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International audience; BACKGROUND : Sickle cell disease (SCD) patients undergo multiple red blood cell (RBC) transfusions and are regularly exposed to low‐prevalence (LP) antigens specific to individuals of African descent. This study evaluated the prevalence of antibodies against LP antigens in SCD patients and the need to identify these antibodies in everyday practice.STUDY DESIGN AND METHODS : Plasma from 211 SCD patients was tested with RBCs expressing the following LP antigens: RH10 (V), RH20 (VS), RH23 (DW), RH30 (Goa), KEL6 (Jsa), and MNS6 (He).RESULTS : Nine LP antibodies were found in eight patients (3.8%): five anti‐RH23, two anti‐RH30, and two anti‐MNS6. The exposure risk, calculated for each LP antigen, was below 3% per RBC unit, for all antigens tested. Thus, in this cohort of transfused SCD patients, the prevalence of LP antibodies was similar to that of antibodies against antigens of the FY, JK, and MNS blood group systems. These findings also reveal the occurrence of anti‐RH23 in SCD patients. No anti‐RH20 or anti‐KEL6 were found, despite the high frequency of mismatch situations.CONCLUSION : These results highlight the immunogenicity of these LP antigens, and the evanescence of antibodies against LP antigens. They also highlight the importance of appropriate pretransfusion testing for patients frequently transfused, who are likely to be exposed to multiple types of blood group antigens.

β-thalassemia, a hereditary blood disorder caused by defective synthesis of hemoglobin β globin chains, leads to ineffective erythropoiesis and chronic anemia that may require blood transfusions. Sotatercept (ACE-011) acts as a ligand trap to inhibit negative regulators of late-stage erythropoiesis in the transforming growth factor β superfamily, correcting ineffective erythropoiesis. In this phase II, open-label, dose-finding study, 16 patients with transfusion-dependent β -thalassemia and 30 patients with non-transfusion-dependent β-thalassemia were enrolled at seven centers in four countries between November 2012 and November 2014. Patients were treated with sotatercept at doses of 0.1, 0.3, 0.5, 0.75, or 1.0 mg/kg to determine a safe and effective dose. Doses were administered by subcutaneous injection every 3 weeks. Patients were treated for ≤22 months. Response was assessed as a ≥20% reduction in transfusion burden sustained for 24 weeks in transfusion-dependent β-thalassemia patients, and an increase in hemoglobin level of ≥1.0 g/dL sustained for 12 weeks in non-transfusion-dependent β-thalassemia patients. Sotatercept was well tolerated. After a median treatment duration of 14.4 months (range 0.6-35.9), no severe life-threatening adverse events were observed. Thirteen percent of patients reported serious but manageable adverse events. The active dose of sotatercept was ≥0.3 mg/kg for patients with non-transfusion-dependent β-thalassemia and ≥0.5 mg/kg for those with transfusion-dependent β-thalassemia. Of 30 non-transfusion-dependent β-thalassemia patients treated with ≥0.1 mg/kg sotatercept, 18 (60%) achieved a mean hemoglobin increase ≥1.0 g/dL, and 11 (37%) an increase ≥1.5 g/dL, sustained for ≥12 weeks. Four (100%) transfusion-dependent β-thalassemia patients treated with 1.0 mg/kg sotatercept achieved a transfusion-burden reduction of ≥20%. Sotatercept was effective and well tolerated in patients with β-thalassemia. Most patients with non-transfusion-dependent β-thalassemia treated with higher doses achieved sustained increases in hemoglobin level. Transfusion-dependent β-thalassemia patients treated with higher doses of sotatercept achieved notable reductions in transfusion requirements. This trial was registered at ClinicalTrials.gov with the number NCT01571635.

Sickle cell disease (SCD) in pregnancy can be associated with adverse maternal and perinatal outcomes. Furthermore, complications of SCD can be aggravated by pregnancy. Optimal prenatal care aims to decrease the occurrence of maternal and fetal complications. A retrospective, French, two-center study compared two care strategies for pregnant women with SCD over two time periods. In the first study period (2005-2010), the women were systematically offered prophylactic transfusions. In the second study period (2011-2014), a targeted transfusion strategy was applied whenever possible, and home-based prophylactic nocturnal oxygen therapy was offered to all the pregnant women. The two periods did not differ significantly in terms of the incidence of vaso-occlusive events. Maternal mortality, perinatal mortality, and obstetric complication rates were also similar in the two periods, as was the incidence of post-transfusion complications (6.1% in 2005-2010 and 1.3% in 2011-2014, P = .15), although no de novo alloimmunizations or delayed hemolysis transfusion reactions were observed in the second period. The results of this preliminary, retrospective study indicate that targeted transfusion plus home-based prophylactic nocturnal oxygen therapy is safe and may decrease transfusion requirements and transfusion-associated complications.

International audience; Silica nanoparticles act as an effector for human native and sickle cell hemoglobin while preserving their tetrameric structure.Manipulating hemoglobin oxygenation using nanoparticles opens the way for the rational design of hemoglobin-based oxygen carriers.Recently, nanoparticles have attracted much attention as new scaffolds for hemoglobin-based oxygen carriers (HBOCs). Indeed, the development of bionanotechnology paves the way for the rational design of blood substitutes, providing that the interaction between the nanoparticles and hemoglobin at a molecular scale and its effect on the oxygenation properties of hemoglobin are finely controlled. Here, we show that human hemoglobin has a high affinity for silica nanoparticles, leading to the adsorption of hemoglobin tetramers on the surface. The adsorption process results in a remarkable retaining of the oxygenation properties of human adult hemoglobin and sickle cell hemoglobin, associated with an increase of the oxygen affinity. The cooperative oxygen binding exhibited by adsorbed hemoglobin and the comparison with the oxygenation properties of diaspirin cross-linked hemoglobin confirmed the preservation of the tetrameric structure of hemoglobin loaded on silica nanoparticles. Our results show that silica nanoparticles can act as an effector for human native and mutant hemoglobin. Manipulating hemoglobin oxygenation using nanoparticles opens the way to the design of novel HBOCs.

International audience; Delayed hemolytic transfusion reaction (DHTR) is a life-threatening complication of transfusion in sickle cell disease (SCD). The frequency of DHTR is underestimated because its symptoms mimic those of vaso-occlusive crisis and antibodies (Abs) are often not detectable. No predictive factors for identifying patients likely to develop DHTR have yet been defined. We conducted a prospective single-center observational study over 30 months in adult sickle cell patients. We included 694 transfusion episodes (TEs) in 311 patients, divided into occasional TEs (OTEs: 360) and chronic transfusion program (CTEs: 334). During follow-up, 15 cases of DHTR were recorded, exclusively after OTEs. DHTR incidence was 4.2% per OTE (95% CI [2.6; 6.9]) and 6.8% per patient during the 30 months of the study (95% CI [4.2; 11.3]). We studied 11 additional DHTR cases, to construct a predictive score for DHTR. The DHTR mortality is high, 3 (11.5%) of the 26 DHTR patients died. The variables retained in the multivariate model were history of DHTR, number of units previously transfused and immunization status before transfusion. The resulting DHTR-predictive score had an area under the ROC curve of 0.850 [95% CI: 0.780-0.930], a negative-predictive value of 98.4% and a positive-predictive value of 50%. We report in our study population, for the first time, the incidence of DHTR, and, its occurrence exclusively in occasionally transfused patients. We also describe a simple score for predicting DHTR in patients undergoing occasional transfusion, to facilitate the management of blood transfusion in SCD patients.

Objective To describe maternal mortality among women with sickle-cell disease in France. Study design Data from the national confidential enquiry into maternal deaths and from reference centres for sickle-cell disease were examined to identify women with this disease who died in France during 1996–2009. The maternal mortality ratio among women with sickle-cell disease was estimated and compared with the ratio in the general population. Characteristics of these women and their pregnancies and circumstances of their deaths were examined in detail. Results Fifteen maternal deaths occurred among an estimated 3300 live births to women with sickle-cell disease, for a maternal mortality ratio of 454 per 100 000 live births (95% CI [254; 750]), versus 9.4/100 000 in the general population. Ten women were homozygous (SS) for sickle-cell disease, and five were composite heterozygotes. The episode leading to death appeared in the antepartum period for seven women (47%). Two women died of septic shock during pregnancy, one at 6 weeks, the other at 24 weeks. The other 13 women (87%) died postpartum. Thirteen deaths were directly attributable to sickle-cell disease. The other two maternal deaths, both considered direct obstetric causes, were due to amniotic fluid embolism and septic shock after post-amniocentesis chorioamnionitis. The expert committee on maternal mortality judged seven of these 15 deaths (47%) to be avoidable. Conclusion Sickle-cell disease is responsible for a major excess risk of maternal death in France, due mainly to direct complications of the disease.

Cardiac involvement is common in sickle cell disease (SCD). Studies are needed to establish haematological determinants of this involvement and prognostic markers. The aim of the study was to identify haematological factors associated with cardiac involvement in SCD and their impact on prognosis.This longitudinal observational study was performed on 1780 SCD patients with SS or S-β(0)-thalassemia referred to our centre. Six hundred fifty-six met our inclusion criteria (availability of a blood-workup and echocardiogram obtained1 year apart, no heart valve surgery and no current pregnancy). Median age was 31 (interquartile range, 25-40) years, and median haemoglobin (Hb) was 87 (80-95)g/L. Left ventricular (LV) dilation, left atrial dilation, cardiac index (CI)4 L/min/m(2), LV ejection fraction55%, and tricuspid regurgitant velocity (TRV) ≥2.5 m/s were found in 35, 78, 23, 8.5, and 17% of patients, respectively. Compared with other patients, those in the fourth quartiles (Q4) of LV end-diastolic dimension index (LVEDDind) and left atrial dimension index (LADind) and those with high CI had significantly lower Hb, % foetal Hb (HbF), and red blood cell (RBC) counts; and significantly higher lactate dehydrogenase, bilirubin, and %dense RBCs. Independent haematologic determinants of Q4 LVEDDind and LADind were low RBC count and %HbF; high %dense RBCs were associated with LADind. Low %HbF and RBC count were associated with high CI. High %dense RBCs or no α-thalassemia gene deletion was associated with greater severity of anaemia and cardiac dilation and with higher CI. During the median follow-up of 48 (32-59) months, 50 (7.6%) patients died. Tricuspid regurgitant velocity ≥ 2.5 m/s was a predictor of mortality. The risk of death increased four-fold when left ventricular ejection fraction55% was present also (P = 0.0001).Cardiac dilation and CI elevation in patients with SCD are associated with haematologic variables reflecting haemolysis, RBC rigidity, and blood viscosity. Tricuspid regurgitant velocity ≥ 2.5 and LV dysfunction (even mild) predict mortality.

Previous clinical trials suggested that inhaled nitric oxide (iNO) could have beneficial effects in sickle cell disease (SCD) patients with acute chest syndrome (ACS). To determine whether iNO reduces treatment failure rate in adult patients with ACS, we conducted a prospective, double-blind, randomized, placebo-controlled clinical trial. iNO (80 ppm, N = 50) gas or inhaled nitrogen placebo (N = 50) was delivered for 3 days. The primary end point was the number of patients with treatment failure at day 3, defined as any one of the following: (1) death from any cause, (2) need for endotracheal intubation, (3) decrease of PaO2/FiO2 ≥ 15 mmHg between days 1 and 3, (4) augmented therapy defined as new transfusion or phlebotomy. The two groups did not differ in age, gender, genotype, or baseline characteristics and biological parameters. iNO was well tolerated, although a transient decrease in nitric oxide concentration was mandated in one patient. There was no significant difference in the primary end point between the iNO and placebo groups [23 (46 %) and 29 (58 %); odds ratio (OR), 0.8; 95 % CI, 0.54–1.16; p = 0.23]. A post hoc analysis of the 45 patients with hypoxemia showed that those in the iNO group were less likely to experience treatment failure at day 3 [7 (33.3 %) vs 18 (72 %); OR = 0.19; 95 % CI, 0.06–0.68; p = 0.009]. iNO did not reduce the rate of treatment failure in adult SCD patients with mild to moderate ACS. Future trials should target more severely ill ACS patients with hypoxemia. NCT00748423.

Polymerization of HbS and cell sickling are the prime pathophysiological events in sickle cell disease (SCD). Over the last 30 years, a substantial understanding at the molecular level has been acquired on how a single amino acid change in the structure of the beta chain of hemoglobin leads to the explosive growth of the HbS polymer and the associated changes in red cell morphology. O2 tension and intracellular HbS concentration are the primary molecular drivers of this process, and are obvious targets for developing new therapies. However, polymerization and sickling are driving a complex network of associated cellular changes inside and outside of the erythrocyte, which become essential components of the inflammatory vasculopathy and result in a large range of potential acute and chronic organ damages. In these areas, a multitude of new targets for therapeutic developments have emerged, with several ongoing or planned new therapeutic interventions. This review outlines the key points of SCD pathophysiology as they relate to the development of new therapies, both at the pre-clinical and clinical levels.

Alloimmunization against red blood cells (RBCs) is the main immunological risk associated with transfusion in patients with sickle cell disease (SCD). However, about 50-70% of SCD patients never get immunized despite frequent transfusion. In murine models, CD4(+) T cells play a key role in RBC alloimmunization. We therefore explored and compared the CD4(+) T-cell phenotypes and functions between a group of SCD patients (n = 11) who never became immunized despite a high transfusion regimen and a group of SCD patients (n = 10) who had become immunized (at least against Kidd antigen b) after a low transfusion regimen. We studied markers of CD4(+) T-cell function, including TLR, that directly control lymphocyte function, and their spontaneous cytokine production. We also tested responders for the cytokine profile in response to Kidd antigen b peptides. Low TLR2/TLR3 expression and, unexpectedly, strong expression of CD40 on CD4(+) T cells were associated with the nonresponder status, whereas spontaneous expression of IL-10 by CD4(+) T cells and weak Tbet expression were associated with the responder status. A Th17 profile was predominant in responders when stimulated by Jb(k) . These findings implicate CD4(+) T cells in alloimmunization in humans and suggest that they may be exploited to differentiate responders from nonresponders.

International audience; No abstract available

International audience; The severity of β-thalassaemia (β-thal) intermedia is mainly correlated to the degree of imbalanced α/non α-globin chain synthesis. The phenotypic diversity of β-thal depends on this imbalance and reflects all possible combinations of α- and β-globin genotypes, levels of fetal haemoglobin (HbF) and co-inheritance of other modulating factors. This study aimed to demonstrate the validity of a new surrogate of α/non α-globin biosynthetic ratio by measuring the soluble α-Hb pool in lysed red blood cells. Our results confirm that the α-Hb pool measurement allows a good discrimination between β-thal intermedia patients, controls and α-thal patients (P < 0·003). Receiver operator characteristic analyses revealed an area under the curve of 0·978 for the α-Hb pool measurement at a threshold of 120 ng free α-Hb/mg of total Hb/ml of haemolysate (ppm) with a sensitivity and specificity of 86% and 100%, respectively, to discriminate between β-thal and not β-thal subjects. Significant correlations were observed between the α-Hb pool and biological parameters of β-thal, the most significant association being observed with red cell hexokinase activity. This study indicates that the α-Hb pool could be a new marker for assistance in diagnostic orientation of β-thal intermedia patients and may be clinically useful for monitoring the evolution of the disequilibrium of globin synthesis in response to treatments.

International audience; No abstract available

Summary The management of sickle cell nephropathy (SCN) at an early stage is an important issue to prevent renal and cardiovascular morbidity and mortality. This study aimed to evaluate in this population, whether angiotensin converting enzyme inhibitors (ACEIs) treatment could exert a cardio-renal protection in a SCN cohort. Forty-two SCN patients (urine albumin:creatinine ratio (ACR) > 10 mg/mmol) were treated with ACEIs for 6 months, then evaluated for ACR, measured glomerular filtration rate (mGFR) together with haematological and cardiovascular parameters. A 1-month washout was also performed in order to differentiate short- and long-term ACEIs effects. A decrease in ACR baseline value (>30%) was detected in 62% of cases (mean ACR: 46·4 ± 7·6 and 26·4 ± 3·9 mg/mmol at baseline and 6 months respectively; P = 0·002), whereas mGFR values were unchanged. ACR decrease was detected at 1 month following ACEI initiation (32·9 ± 6·9, P = 0·02) with a persistent trend after withdrawal (P = 0·08). ACEIs also decreased diastolic blood pressure (P = 0·007), pulse wave velocity (P = 0·01), tricuspid regurgitation velocity (TRV; P = 0·04), asymmetric dimethyl arginine (ADMA: P = 0·001) and haemoglobin (P = 0·01) while conventional haemolytic biomarkers were unchanged. Our data suggest that ACEIs are safe and effective at decreasing albuminuria in sickle cell patients with a beneficial effect on specific mortality risk factors, such as TRV and asymmetric dimethyl arginine.

Background. Optimal modalities for diagnosis, treatment, and surveillance of portal or splenic vein thrombosis have not yet been defined. The present retrospective study aimed to investigate the role of computed tomography performed systematically before and after laparoscopic splenectomy to assess the incidence of portal or splenic vein thrombosis, predictors, and outcomes. Methods. Computed tomography scans were obtained from 170 patients undergoing elective laparoscopic splenectomy between 2005 and 2015. Pre- and postoperative splenic vein diameter was measured at the splenoportal junction and at a distance of 2, 4, 6 cm from it. Univariate and multivariate analyses were used to identify portal or splenic vein thrombosis risk factors and predictors of treatment outcome. Results. Overall, 68.2% of patients had benign hematologic diseases; 64.1% showed splenomegaly. Portal or splenic vein thrombosis occurred in 53.5% of patients (91/170), of whom 49.5% were asymptomatic. Preoperative splenic vein diameter measurements at 2, 4, and 6 cm from the splenoportal junction were significantly greater in portal or splenic vein thrombosis patients than in no-portal or splenic vein thrombosis patients. Patients with splenic vein diameter $8 mm at all measured sites had a greater risk of developing portal or splenic vein thrombosis (P = .009; odds ratio, 2.57; 95% confidence interval, 1.26–5.23). The majority of thromboses involved the distal splenic vein (45.1%, 41/91), and 41.7% of patients had thromboses located in multiple sites. Fully 71.4% showed complete resolution of portal or splenic vein thrombosis. Thrombus location at a single site predicted a favorable treatment outcome (P < .0001). Conclusion. Portal or splenic vein thrombosis is a frequent complication of splenectomy that occurs asymptomatically in half of cases. Computed tomography could have an important role in identifying patients at risk of developing portal or splenic vein thrombosis as well as in predicting portal or splenic vein thrombosis resolution. (Surgery 2017;162:1219-30.)

Pulmonary artery thrombosis (PAT) is involved in lung vascular dysfunction during acute chest syndrome (ACS) complicating sickle cell disease (SCD). No clinical score is available to identify patients eligible for multi-detector computed tomography (MDCT) angiography during ACS. This retrospective study aimed to develop a risk score for PAT during ACS (PAT-ACS risk score). Patients with SCD were investigated by MDCT during ACS. A logistic regression was performed to determine independent risks factors for PAT and to build the PAT-ACS risk score. A total of 43 episodes (11·9%) of PAT were diagnosed in 361 episodes of ACS. Multivariate analysis identified four risk factors, which were included in the PAT-ACS risk score: a baseline haemoglobin >82 g/l, the lack of a triggering factor for ACS, a platelet count >440 × 109 /l and a PaCO2

Silent white matter changes (WMCs) on brain imaging are common in individuals with sickle cell disease (SCD) and are associated with cognitive deficits in children. We investigated the factors predictive of WMCs in adults with homozygous SCD and no history of neurological conditions. Patients were recruited from a cohort of adults with homozygous SCD followed up at an adult sickle cell referral center for which steady-state measurements of biological parameters and magnetic resonance imaging scans of the brain were available. WMCs were rated by consensus, on a validated age-related WMC scale. The prevalence of WMCs was 49% (95% confidence interval [CI], 39%-60%) in the 83 patients without vasculopathy included. In univariable analysis, the patients who had WMCs were more likely to be older (P = .003) and to have hypertension (P = .02), a lower mean corpuscular volume (P = .005), a lower corpuscular hemoglobin concentration (P = .008), and a lower fetal hemoglobin percentage (%HbF) (P = .003). In multivariable analysis, only a lower %HbF remained associated with the presence of WMCs (odds ratio [OR] per 1% increase in %HbF, 0.84; 95% CI, 0.72-0.97; P = .021). %HbF was also associated with WMC burden (P for trend = .007). Multivariable ordinal logistic regression showed an inverse relationship between WMC burden (age-related WMC score divided into 4 strata) and HbF level (OR for 1% increase in %HbF, 0.89; 95% CI, 0.79-0.99; P = .039). Our study suggests that HbF may protect against silent WMCs, decreasing the likelihood of WMCs being present and their severity. It may therefore be beneficial to increase HbF levels in patients with WMCs.

Background: Sickle cell disease (SCD) is one of the most commonly inherited diseases worldwide and one of the most frequently occurring genetic disorders in France. Delayed hemolytic transfusion reaction (DHTR) is a classic complication in patients with SCD who undergo blood transfusions, and this condition may lead to hyperhemolysis syndrome (HS). DHTR is described as a transfusion complication and is often associated with anti-RBC antibodies. Case report: We report the death of a 47-year-old man of Martinican origin, with sickle cell disease (SCD) and no history of alloimmunization, who was admitted to the Sens Medical Center in July 2015 due to a vaso-occlusive crisis (VOC). An antibody screening test based on the gel technique was conducted and no anti-RBC antibodies were detected. The patient was readmitted with a VOC two days after discharge and subsequently developed DHTR/HS after transfusion episodes. He succumbed to acute complications involving severe multiple organ failure after being transferred to Henri-Mondor University Hospital in Creteil. This case report was made available thanks to our Haemovigilance Network. Conclusion: This case demonstrates the importance of DHTR prevention using national guidelines to carefully assess indications for RBC transfusion in patients with SCD. Early diagnosis is crucial to prevent this life-threatening complication. Special attention should be given to less well-known and less-well monitored patients who may be at high risk for DHTR. In any event, DHTR/HS without detectable anti-RBC antibodies presents a clinical and biological challenge to our understanding of this disorder.

Sickle cell disease (SCD) is a chronic inflammatory disease associated with multiple organ damage, chronic anemia, and infections. SCD patients have a high rate of alloimmunization against red blood cells (RBCs) following transfusion and may develop autoimmune diseases. Studies in mouse models have suggested that regulatory T cells (Treg) play a role in alloimmunization against RBC antigens. We characterized the phenotype and function of the Treg cell population in a homogeneous cohort of transfused SCD patients. We found that the distribution of Treg subpopulations differed significantly between SCD patients and healthy blood donors. SCD patients have a particular Treg phenotype, with strong CTLA-4 and CD39 expression and weak HLA-DR and CCR7 expression. Finally, we show that this particular phenotype is related to SCD rather than alloimmunization status. Indeed, we observed no difference in Treg phenotype or function in vitro using autologous feeder cells between strong and weak responders to alloimmunization.

Strokes are one of the most severe complications of sickle-cell disease. Most studies have been restricted to children with sickle-cell disease. To better understand the characteristics and follow-up of strokes occurring from childhood to adulthood, we undertook a retrospective cohort study of 69 stroke patients among the 2,875 patients consulting at the French Adult Sickle-Cell Disease Referral Center. Between 1970 and 2008, they had experienced 104 strokes: 80 ischemic, 22 hemorrhagic, and 2 intracranial sinus thromboses. Coma and/or fatal outcomes underscored the severity of strokes in sickle-cell disease patients.Hemorrhagic strokes occurred mostly in adults and carried a higher risk of death than ischemic stroke. The mechanisms underlying sickle-cell disease associated strokes were reevaluated and etiologies were determined for first stroke and recurrences, in childhood and adulthood. Sickle-cell disease vasculopathy concerned only SS patients and remains their most frequent stroke etiology. Cardioembolism, vaso-occlusive crisis and triggering factors were other etiologies identified in adults. Recurrences occurred in 19 SS patients only after a first ischemic stroke. SC patients' strokes occurred in adulthood and were associated with cardiovascular risk factors. Our findings provide novel information about cerebrovascular pathologies throughout the lives of sickle-cell disease patients and suggest the need for different diagnostic and therapeutic management approaches in those different settings.

SummaryBackground Leg ulcers (LUs) are a chronic and severe complication of sickle cell disease (SCD). A prospective study in patients with SCD to identify factors associated with complete healing and recurrence of LUs is lacking. Objectives To determine clinical and biological factors associated with SCD-LU complete healing and recurrence. Methods This prospective, observational cohort study was conducted at two adult SCD referral-centre sites (2009–2015) and included 98 consecutive patients with at least one LU lasting ≥ 2 weeks. The primary end points compared patients with healed vs. nonhealed LUs at week 24, and patients with vs. without recurrence during follow-up. Results The median (interquartile range) LU area, duration and follow-up were, respectively, 6·2 cm2 (3–12·8), 9 weeks (4–26) and 65·8 weeks (23·8–122·1). At week 24, LUs were healed in 47% of patients, while 49% of LUs recurred. Univariate analyses identified inclusion LU area < 8 cm2 (82% vs. 35%; P < 0·001), inclusion LU duration < 9 weeks (65% vs. 35%; P = 0·0013) and high median fetal haemoglobin level (P = 0·008) as being significantly associated with complete healing at week 24, and low lactate dehydrogenase level (P = 0·038) as being associated with recurrence. Multivariate analyses retained LU area < 8 cm2 (odds ratio 6·73, 95% confidence interval 2·35–19. 31; P < 0·001) and < 9 weeks’ duration (OR 3·19, 95% confidence interval 1·16–8·76; P = 0·024) as being independently associated with healing at week 24. Factors independently associated with recurrence could not be identified. Conclusions SCD-LU complete healing is independently associated with the clinical characteristics of LUs rather than the clinical or biological characteristics of SCD.

Introduction La drepanocytose, l’hemoglobinopathie congenitale la plus frequente dans le monde est une cause croissante de maladie renale chronique et est a l’origine d’une morbimortalite considerable. Les femmes drepanocytaires sont a haut risque de complications au cours de la grossesse, notamment de pre-eclampsie (PE), cependant, le pronostic renal a long terme n’a jamais ete evalue chez ces patientes. Patients/materiels et methodes Etude cas-temoin dans 2 centres Parisiens entre 2011 et 2016 incluant les femmes presentant un syndrome drepanocytaire majeur et un episode de PE appariees a un groupe de patientes drepanocytaires (groupe T) n’ayant pas presente de PE au cours de la grossesse et appariees sur le genotype et la date du debut de grossesse. Resultats Nous avons identifie 30 patientes drepanocytaires avec un episode de PE et 30 T (60 seront recueillies au total). Le suivi moyen etait de 4 ans dans le groupe PE versus 3,4 ans dans le groupe T. La PE survenait, en moyenne, a 33 SA avec, comme criteres de severite : 3 HELLP syndrome, 1 eclampsie et 13 insuffisances renales aigues stade 1 selon les criteres KDIGO. La moyenne d’âge etait de 30 ans dans le groupe PE versus 29 ans chez les T (p = 0,6). Il n’y avait pas de difference significative entre les patientes PE et les T concernant l’hemoglobine de base : 8,7 g/dL versus 8,5 g/dL et les LDH : 522 ui/L versus 402 ui/L respectivement. Le DFG de base etait de 139 mL/min/1,73 m2 dans le groupe PE versus 149 mL/min/1,73 m2 dans le groupe T (p = 0,2). On notait 78 % de cesariennes dans le groupe PE contre 56 % dans le groupe T (p = 0,1). Le poids de naissance des nouveaux nes etait de 2037 g versus 2268 g a un terme de 34 SA versus 36 SA dans les groupes PE et T respectivement (p = 0,2). Au sein du groupe PE, la creatinine etait significativement plus elevee au moment de la PE par rapport au controle 3 mois plus tard (60 μmol/L versus 43 μmol/L respectivement, p = 0,02). A la fin du suivi, le DFG moyen etait de 127,1 mL/min/1,73 m2 dans le groupe PE versus 146,6 mL/min/1,73 m2 dans le groupe T (p = 0,04). Discussion L’association drepanocytose et PE pourrait s’expliquer par l’ischemie-reperfusion iterative favorisee par la falciformation des globules rouges entrainant un relargage de facteurs pro-angiogeniques dans la circulation. Conclusion Les donnees preliminaires de ce travail suggerent que la pre-eclampsie pourrait entrainer une degradation acceleree de la fonction renale chez les patientes drepanocytaires.

Introduction: Hemolytic anemia combines 3 components to various extents: extravascular hemolysis, intravascular hemolysis and dyserythropoiesis. Global hemolysis in excess to defense lines induces oxidative and inflammatory syndromes and vascular damages in various organs. Therefore, accurate hemolysis biomarkers are required for a better evaluation of hemolytic disorders, such as sickle cell disease (SCD) or thalassemia syndromes and to evaluate the efficacy of various therapies. Accordingly, we have developed a new spectrophotometric method to measure and calculate several hemolysis biomarkers in plasma or serum including Hemoglobin in various forms (HbO2, HbCO, MetHb), Heme or Hemin bound to albumin or to hemopexin, total bilirubin and total hemopexin. Patients and Method : Blood samples were collected at steady-state for 77 SCD adults (mean age 39.8 ± 10.2 yrs, M/F ratio 0.64) and 23 beta thalassemia patients (mean age 42.7 ± 16 yrs, M/F ratio 0.91); SCD patients (SS or Sb0-Thalassemia) were either treated with Hydroxycarbamide (HU: 27) or not (NT: 50). For comparison, plasma samples from healthy volunteers (HV) were also analyzed. Continuous variables were expressed as means ± SD or medians [interquartile range], depending on their normal or asymmetric distributions. Categorical variables were expressed as numbers (%). Univariate analyses were done using Student's t-test or Mann-Whitney non-parametric test, depending on the distribution. Correlation were analyzed using a spearman test. The dosage methodology is based on the light absorption spectrophotometry of plasma samples using an appropriate mathematical conversion of the signal, reference spectra of the different species and some chemical modifications of the iron redox and ligation states. Results: The levels of plasma Hb were statistically higher in homozygous SCD patients compared to beta-thalassemia patients (p=0.001) and healthy volunteers, with median of 6.3 [3.4-11], 2.6 [1-5.4] and 1.7 [0.5-3] µM respectively (Table 1). Interestingly levels of plasma heme were higher in beta thalassemia patient compared to SCD patients (p=0.0001) and HV, with a mean of 1.05 [0.05-3], 10.5 [3.5-24] and ≤ 0.2 µM level of detection respectively (Table 1). A significant negative correlation was found between heme and hemopexin levels in both diseases (p Discussion and Conclusions: plasma Hb is a more accurate dosage for intra vascular hemolysis than other biomarkers which are not specific of intra vascular hemolysis and could be biased by other pathological conditions: LDH or ASAT can be increased in hepatic or muscular cytolysis, bilirubin is dependent on the heme oxygenase and glycuronyl transferase activities, and reticulocytes are dependent on erythropoiesis. Our results showed that the intra-vascular hemolysis is more pronounced in SCD compared to beta-thalassemia based on the plasma Hb levels. The elevated plasma heme concentration in beta thalassemia is a new finding that should be investigated in more details. It could reflect the ineffective erythropoiesis or heme export from erythroblasts or macrophages involving hemopexin scavenging. Disclosures Bencheikh: Hemanext: Research Funding. Bartolucci:HEMANEXT: Membership on an entity's Board of Directors or advisory committees; AddMedica: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.

Background: Transfusion is a major therapeutic of sickle cell disease (SCD); however, DHTR is one of the most feared complications . Prevention of allo immunization, by extended RBC matching is insufficient to prevent all cases of DHTR. Therefore, B cell depletion therapy should be also useful, especially in previously immunized patients to avoid the emergence of new allo-antibodies. Rituximab (RTX) is used for preventing alloimmunization for patients with a history of DHTR. Therefore, secondary prevention with rituximab prior a new exposure to transfused RBCs could be a relevant option. Here, we will report our experiences of RTX use in SCD adult patients with a previous history of DHTR. Methods: In this retrospective observational study, the data from 58 consecutive RTX infusion in 44 SCD patients with history of DHTR in our French referral center for SCD were analysed. Medical, biological and blood bank records of patients, clinical signs, rate of hemoglobin A (HbA) after transfusion (TF) were collected. To evaluate the persistence of transfused RBCs, the DHTR risk probability on days 15 and 30 after TF was evaluated according to Mekontso Dessaps nomogram. We also reported serious adverse events like infections in the year after RTX infusion. In cases of programmed surgery, 1 gramme of RTX was administred at day 1 and 15 few weeks before or one injection in emergency situation, with low dose of steroides. Adjuvant measure to avoid transfusion like EPO, Iron injection and hydroxyurea was decided in some cases. Results: We analyzed 58 cases of RTX administered to 44 adult patients with SCD, 10 of whom received two or more times this drug. A transfusion (TF) was required in 33/58 cases (56%). We distinguished three groups of patients. In the first group of 21 cases (36%), rituximab was used preventively before planned surgery at risk of bleeding, only 8 cases were transfused. In the second group of 30 cases (53%) during an acute event, in 19 cases patients received a transfusion. The third group of 7 patients received RTX during an active DHTR with hyperhemolysis requiring transfusion to protect an imminent transfusion and finally 6 of them was transfused. To evaluate the efficacy of transfusion we analyzed group 1 and 2 together and separately the third group with active DHTR and hyperhemolysis. In the first and second groups, HbA measurements was not available or interpretable in 11,1% of cases. On day 15 after TF, 77,8% of cases were classified as having a low probability of hemolysis, 7.4 % as intermediate probability and 3.7% as high probability. On day 30 after TF: 55,6% were into the low probability of hemolysis subgroup, 11,1% in the intermediate probability and 22,2% in the high probability group. (Figure 1) In group 3, HbA measurement wasn't available in 2 cases. On day 15 after TF, no cases were classified as having a low probability of hemolysis, 33,3 % as intermediate probability and 33.3% as high probability. On day 30 after TF: 33,3% were in the intermediate probability and 50 % in the high probability group. (Figure 2) Infection requiring intravenous antibiotic were observed in 19 cases/58 (32.7%) with a bacterial documentation in 73,7 %. In 63% of these cases, patients have been hospitalized in intensive care unit for acute events before RTX administration and had other risk factors of infection. The median time of apparition of infection was 28 days [11.5-46.5]. We report 4 deaths (6,8%), two patient died due to a hyperhemolysis syndrome with multiorgan failure that started before RTX administration, two other were due to an end stage cancer. These deaths are not related to the use of RTX. Conclusion: This study suggests that RTX can be safely used for preventing DHTR in patients with a previous history of DHTR and detected antibodies. We show that transfusion efficiency at day 15 post TF is better than days 30 postTF. The effectiveness of TF in active DHTR with h yperhemolysis is much lower, as most patients lose the transfused units at day 30 post TF.Beyond the use of RTX, the use of other measures such as hydroxyurea and erythropoietin to avoid the need of transfusion in these patients must be emphasized. Infection risk after RTX therapy is difficult to assess. In most cases an active inflammatory event was in process. Additional prospective studies are needed to improve the management of this challenging clinical situation. Disclosures Michel: Novartis: Consultancy; Amgen: Consultancy; Rigel: Consultancy. Galactéros:Addmedica: Membership on an entity's Board of Directors or advisory committees. Bartolucci:Novartis: Membership on an entity's Board of Directors or advisory committees; AddMedica: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; HEMANEXT: Membership on an entity's Board of Directors or advisory committees; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees.

Introduction: Over the past decades, there have been substantial improvements in the medical care of sickle cell patients, leading to an increase in life expectancy, despite the fact that the latest studies in adults do not see any change in age at death. Pediatric mortality has declined significantly with the introduction of systematic antibiotics, the preventive care cerebral vasculopathy and therapeutic education for families. It seems important to analyze the morbidity and mortality risks to decide the necessary preventive measures. In this study we will describe the circumstances of death, the profiles of the patients and the risk factors in SCD adult patients. Materiel and method: We retrospectively reviewed the records of patients which died between 2001 and 2019 and treated in our national referral center (Henri Mondor Hospital) where 3500 patients are followed. Basic biological parameters, chronic and acute complications present in these patients as well as their treatment, median age at death, causes and circumstances of death were identified when the information was available. Results: During this period, 198 deaths were recorded or reported by families of patients. 54% were men. Patients ranged in age from 16 to 69 years and median age at death was 37 years IQR [30-47]. Concerning the type of hemoglobinopathy there were 158 homozygous patients (77%), 28 SC (14%), 11 heterozygous Sβ0 (5%) and 4 heterozygous Sβ+(2%).The causes of death are summarized in the Table 1. Patients had chronic terminal stage organ failure in more than 30% of cases, with indication for organ transplantation (renal, hepatic or cardiac) in 60 of them and 10 precapillary PAHs. 18% of patients were dialyzed. The diagnosis of DHTR was not reported in previous studies and probably under-diagnosed but 12 (6%) patients died of hyperhemolysis with multi-organ failure in this study. Nine deaths occurred during pregnancy and 17 during a travel. Biological, echo graphics data and risk factor analysis is ongoing. Discussion: The median age of death does not seem to improve from the study of Platt et al, however our cohort appears to age, we observed an increase in the number of aged patients over 45. The causes of death have evolved compared to data avaliable from previous studies, chronic organ failures are the leading cause of mortality especially in patients with renal impairment. The prevention of the onset of these complications is one of the new challenges especially renal diseases which was associated with premature mortality. DHTR and brain hemorrhages are new entities probably previously under-diagnosed. Pregnancy remains a risk period, which should strengthen its monitoring. Table 1 Disclosures Michel: Novartis: Consultancy; Rigel: Consultancy; Amgen: Consultancy. Galactéros:Addmedica: Membership on an entity's Board of Directors or advisory committees. Bartolucci:Roche: Membership on an entity's Board of Directors or advisory committees; HEMANEXT: Membership on an entity's Board of Directors or advisory committees; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; AddMedica: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Hydroxyurea (HU) is approved in EU and USA for the prevention of vaso-occlusive crises (VOC) including acute chest syndromes (ACS) in patients over 2 years with sickle-cell disease (SCD). Patients on HU wishing to conceive should stop treatment 3 to 6 months before pregnancy if possible. Pregnancy in SCD female patients are considered at risk for the mother and the fetus. This condition is associated with increased pain, infections, thromboembolic events,[1] and vaso-occlusion in placenta can lead to adverse fetal outcomes.[2] A few cases of HU exposure during pregnancy in SCD patients previously published[3],[4] suggested that the risk of deleterious teratogenic effect of HU shown in animal species[5] may have been overestimated in humans.[6] Therefore, a much larger dataset of pregnancies with HU exposure was needed. ESCORT-HU study (European Sickle Cell Disease COhoRT - HydroxyUrea) is a multicentric, prospective, non-interventional European study initiated to collect information about long-term safety of HU when used in current practice. This is the first study in which all pregnancy courses were collected irrespectively of action taken with HU before or during pregnancy. Overall 1906 patients were enrolled from 63 centers in France, Germany, Greece and Italy, 854 men (45%) and 1052 women (55%) among them around 2/3 aged from 15 to 49 years during the follow-up. During the study, 125 pregnancies in 101 women and 12 pregnancies in 10 partners of male patients were collected in the study, regardless HU exposure. In pregnancies with HU paternal exposure, 10 live births and 2 miscarriages were reported. Durations of HU exposure and outcomes of pregnancies in females treated with HU are provided in Table 1. The mean age at the pregnancy was 30 years. The mean HU duration before pregnancy was nearly 5 years. In only 16 pregnancies with maternal exposure (15%) HU was stopped at least 15 days before conception. In 43 pregnancies (34%), transfusions were reported. Live births were reported in 73% of pregnancies with maternal HU exposure excluding voluntary abortions. There was no statistical difference (Chi-squared test) in the proportions of live birth in exposed and non-exposed females (p=0.577). VOC or ACS have been reported in 3 women after the stop of HU. Although women are advised to stop HU before pregnancy, in current practice continuation of HU may be required and HU remains the only alternative to protect the mother and the fetus from deleterious effects of VOC. In conclusion, the data on pregnancy outcome following HU exposure are reassuring when compared to those in general SCD population. Overall in ESCORT-HU, 61% of pregnancies resulted in live birth, which is more than the 42% of pregnancies in the MSH study participants.4 It is notable, without considering voluntary abortions, that the percentage of live birth in ESCORT-HU reached 71%. The rate of preterm delivery (13%) was similar to the one (16%) in HbSS patients from a French cohort.[7] The fertility in women treated with HU seems to be even better and no particular problem in newborns has been reported to date. Disclosures Galactéros: Addmedica: Membership on an entity's Board of Directors or advisory committees. Cannas:Addmedica: Membership on an entity's Board of Directors or advisory committees. Bartolucci:AddMedica: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; HEMANEXT: Membership on an entity's Board of Directors or advisory committees. Voskaridou:Addmedica: Membership on an entity's Board of Directors or advisory committees; Acceleron: Consultancy, Research Funding; Genesis: Consultancy, Research Funding; Protagonist: Research Funding; Celgene Corporation: Consultancy, Research Funding.

Introduction: Fetal hemoglobin (HbF) expression is a major modulator of sickle cell disease (SCD) severity by decreasing the HbS polymerization. However, the distribution of HbF in red blood cells (RBC) is heterogeneous in SCD patients. In the hypothesis of an HbF "threshold" in RBCs for inhibiting the HbS polymerization, accurate measurement of the HbF content in each red blood cell (HbF/RBC) is mandatory. To this purpose we developed a new and accurate method allowing the direct measurement of HbF content per RBC. Thanks to it, as a proof of concept, we analyzed HbF distribution and content in RBC from SCD patients before and after 6 months of treatment by hydroxyurea (HU). To determine if a threshold of HbF/RBC could modulate SCD, we analyzed the associations between the %RBC reaching different thresholds of HbF (in picograms), and biological parameters and the incidence of severe VOC. Methods: 14 SCD (βS/βS or βS/β0) patients were included to study HbF distribution during HU for a period of 6 months. RBCs were collected during each outpatient visit (Week 0, Week 2, Week 4, Week 12, and ≥ Week 24). HbF content was measured in RBCs using an anti-Human-HbF antibody by flow cytometry. Normalized RBC fluorescence intensity was then converted in picograms of HbF/RBC by using the linear association between mean HbF content and mean RBC fluorescence obtained from subjects presenting homogeneous HbF distribution (patients with hereditary persistence of HbF (HPFH), or β-Thalassemia or δβ-Thalassemia). Quantitative analysis were performed before and during HU treatment to characterize the response by comparing percentages of RBC classes based on different ranges of HbF/RBC during HU treatment. We therefore analyzed the associations between HbF/RBC thresholds (%RBC containing at least 2, 4, 6, 8, 10 or 20 pg HbF) and biological parameters before and ≥ 6 months of HU treatment. Finally HbF/RBC thresholds at Week 0 were compared to the incidence of hospitalized VOC within 3 years before W0, and HbF/RBC thresholds at Week 24 were compared to the incidence of hospitalized VOC within 3 years after W24 at a stable dose. Results: After 6 months of HU, mean %HbF, assessed by HPLC, raised from 6.16% (±3.5) to 15.2% (±8.7) (mean ± standard deviation). Quantitative analysis of HbF/RBC revealed a statistically significant decrease between D0 and ≥M6 of 24% of RBCs containing less than 2 pg (p = 0.0015) and a 2-fold increase of RBCs containing between 2 and 4 pg (p = 0.0025) (Friedman test). For biological parameters we observed an increase in mean %HbF, MCV and MCH and a decrease in RBC count significantly associated (p The incidence of VOC within 3 years after HU treatment was not statistically significant than during the 3 years before (p = 0.4414 - Wilcoxon test). VOC incidence under treatment decreased in 6/14 patients, did not change in 4/14 and increased in 4/14. The incidence of VOC over 3 years was not associated with the %HbF assessed by HPCL (r = -0.0358; p = 0.8564 - Spearman test). We observed a statistically significant correlation between the incidence of VOC over 3 years and the HbF threshold of 4 pg (r = -0.5068; p = 0.0059). We therefore determined the percentage of RBCs by thresholds of HbF, associated to ≤ 1 VOC over 3 years (Table 1). For example, if more than 20% RBCs have ≥ 4 pg of HbF, we calculated a sensitivity and a specificity of 58.3% and 100% respectively, and a positive and a negative predictive value of 100.0% and 76.2% respectively, to have ≤ 1 VOC over 3 years. Conclusion: Our results strengthen the hypothesis that the percentage of RBC above a threshold of HbF is the important parameter to measure. These results need to be replicated in a larger cohort but they open up interesting prospects for analysis of new therapeutic efficacy, including gene therapy and HbF inducers. Disclosures Galactéros: Addmedica: Membership on an entity's Board of Directors or advisory committees. Bartolucci:Agios: Membership on an entity's Board of Directors or advisory committees; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; HEMANEXT: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; AddMedica: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.

Background: Pyruvate kinase (PK) deficiency is a congenital hemolytic anemia caused by mutations in the PKLR gene, leading to a deficiency of the glycolytic enzyme red cell PK (PK-R). Current treatments for PK deficiency are supportive only. Mitapivat (AG-348) is an oral, small-molecule, allosteric PK-R activator in clinical trials for PK deficiency. We previously described results from DRIVE PK, a phase 2, randomized, open-label, dose-ranging study in adults with PK deficiency (N=52) treated with mitapivat for a median of 6 months. Aim: To report long-term safety and efficacy of mitapivat in patients who continue treatment in the ongoing Extension period of the DRIVE PK study (ClinicalTrials.gov NCT02476916). Methods: Patients were eligible to participate if ≥18 years of age with a confirmed diagnosis of PK deficiency (enzyme and molecular testing); baseline hemoglobin (Hb) levels ≤12.0 g/dL (males) or ≤11.0 g/dL (females); and if they had not received more than 3 units of red blood cells in the prior 12 months, with no transfusions in the prior 4 months. Patients were initially randomized 1:1 to receive mitapivat 50 mg twice daily (BID) or 300 mg BID for a 6-month Core period. Dose adjustment was allowed during the Core period based on safety and efficacy. Patients experiencing clinical benefit without concerning safety issues related to mitapivat (investigator discretion) could opt to enter the Extension period, with follow-up visits every 3 months. Safety (adverse events [AEs]) and efficacy (hematologic parameters including Hb) were assessed. Protocol amendments during the Extension period required that (1) patients who did not have an increase from baseline Hb of ≥1.0 g/dL for ≥3 of the prior 4 measurements withdraw from the study, and (2) patients treated with mitapivat doses >25 mg BID undergo a dose taper and continue on the dose that maintained their Hb level no lower than 1.0 g/dL below their pre-taper Hb level. Results: Fifty-two patients enrolled in this study and were treated in the 24-week Core period; 43 (83%) patients completed the Core period and 36 (69%) entered the Extension period. Eighteen patients discontinued from the Extension period: investigator decision (n=8), AEs (n=1), consent withdrawal (n=1), noncompliance (n=1), or other (n=7). Thus, 18 patients, all of whom received ≥29 months of treatment with mitapivat (median 35.6, range 28.7-41.9) have continued treatment. Ten of these 18 patients were male, 11 had a prior splenectomy, and 5 had a history of iron chelation. Median age was 33.5 (range 19-61) years; mean baseline Hb was 9.7 (range 7.9-12.0) g/dL. All patients had ≥1 missense PKLR mutation. The doses (post-taper) at which treatment was continued were (BID): ≤25 mg (n=12), 50 mg (n=5), and 200 mg (n=1). Improvements in Hb levels and markers of hemolysis (reticulocytes, indirect bilirubin, haptoglobin) were sustained (Figure). Among the 18 patients, headache was the most commonly reported AE during both the Extension (n=7, 38.9%) and Core (n=10, 55.6%) periods. Reports of insomnia and fatigue during the Extension period (n=5, 27.8% each) were the same as or similar to those during the Core period. There were fewer reports of nausea (2 vs 6) and hot flush (0 vs 5) in the Extension period. Nasopharyngitis was reported in 5 patients in the Extension period vs 1 patient in the Core period. These data are consistent with the AE profile for the 52 patients treated overall in the Core period, in that headache (44%), insomnia (40%), and nausea (38%) were the most commonly reported AEs and were transient (generally resolved within 7 days without intervention). Conclusion: Chronic daily dosing with mitapivat for a median of 3 years was well tolerated, with no new safety signals reported. Increased Hb levels and improvements in hemolysis markers were sustained at the optimized individual doses. These long-term data support the potential of mitapivat as the first disease-altering therapy for PK deficiency. Two phase 3 trials are underway to further study the effect of mitapivat in patients with PK deficiency. Disclosures Grace: Novartis: Research Funding; Agios Pharmaceuticals, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Layton:Novartis: Membership on an entity's Board of Directors or advisory committees; Cerus Corporation: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees. Galactéros:Addmedica: Membership on an entity's Board of Directors or advisory committees. Barcellini:Novartis: Research Funding, Speakers Bureau; Alexion: Consultancy, Research Funding, Speakers Bureau; Apellis: Consultancy; Incyte: Consultancy, Other: Advisory board; Agios: Consultancy, Other: Advisory board; Bioverativ: Consultancy, Other: Advisory board. van Beers:Agios Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Research Funding; RR Mechatronics: Research Funding. Ravindranath:Agios Pharmaceuticals, Inc.: Other: I am site PI on several Agios-sponsored studies, Research Funding. Kuo:Agios: Consultancy; Alexion: Consultancy, Honoraria; Apellis: Consultancy; Bioverativ: Other: Data Safety Monitoring Board; Bluebird Bio: Consultancy; Celgene: Consultancy; Novartis: Consultancy, Honoraria; Pfizer: Consultancy. Sheth:Apopharma: Other: Clinical trial DSMB; CRSPR/Vertex: Other: Clinical Trial Steering committee; Celgene: Consultancy. Kwiatkowski:bluebird bio, Inc.: Consultancy, Research Funding; Apopharma: Research Funding; Novartis: Research Funding; Terumo: Research Funding; Celgene: Consultancy; Imara: Consultancy; Agios: Consultancy. Hua:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Hawkins:Bristol Myers Squibb: Equity Ownership; Infinity Pharma: Equity Ownership; Agios: Employment, Equity Ownership; Jazz Pharmaceuticals: Equity Ownership. Mix:Agios: Employment, Equity Ownership. Glader:Agios Pharmaceuticals, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Hydroxyurea (HU) is approved in the EU and USA for prevention of vaso-occlusive crises (VOC) including acute chest syndromes (ACS) in patients over 2 years with sickle-cell disease (SCD). The major benefits of HU in SCD are directly related to its abilities to increase HbF, decrease sickling of red blood cells and hemolysis, leading to reduction of vaso-occlusive episodes, need for blood transfusions and consequently reduction of morbidity and mortality. Adherence to the treatment is paramount for effectiveness, but in spite of proven benefits, barriers to adherence persist.[1] ESCORT-HU study (European Sickle Cell Disease COhoRT - HydroxyUrea), is a multicentric, prospective, non-interventional European study designed to evaluate the safety profile of HU in real life. Patients were enrolled from January 2009 to June 2017 with a follow-up of up to 10 years. All interruptions and resumptions of HU treatment exceeding 15 days were recorded in this study. We hereby present the analysis of the group of patients who self-discontinued HU at least once during the study before informing their caregiver, with a view to identify potential barriers to long-term adherence. In total, 1906 patients were enrolled in ESCORT-HU from 63 centers in France, Germany, Greece and Italy. Of these, 619 patients (32%) stopped HU for over 15 days at least once, and around a third (11% of all patients) were due to patient's will. The mean duration of HU treatment before the first discontinuation was 4.8 ± 5.1 years. Data are summarized in table 1. Compared to the rest of the cohort, the 'treatment discontinuation' group had similar distribution by gender and indication for HU prescription, but a higher proportion of adults stopped HU more than 15 days. It is notable that the proportion of patients with SC genotype was higher in the 'treatment discontinuation' group (4.5% vs 1.7%). The patients in the 'treatment discontinuation' group had more frequent SCD symptoms before enrolment in the study (table 2). Hematological and clinical improvement compared to the baseline was observed in both groups. However, average mean Corpuscular Volume (MCV) and Fetal Hemoglobin percentage (HbF%) were lower and mean percentages of patients with SCD symptoms were higher over the three years of follow-up in the 'treatment discontinuation' group, suggesting that HU daily dose was insufficient (table 2). Sixty patients have no treatment resumption date reported which suggest a permanent interruption of their treatment. Among them 32% preferred to switch to another HU medicinal product and 13% have safety issue (table 3). Understanding and managing self-discontinuation of HU before taking medical advice is challenging for the physician. It is tempting to speculate that it may be due, at least in part, to lack of effectiveness potentially due to an underdosage of the treatment. Resistance to the treatment may also be suggested based on past literature data revealing a great variability in the response (determined by HbF%) to HU therapy. There is evidence that genetic modifiers affect individual response to HU.[2],[3] Finally, weariness from long-term use may also explain the patient's wish to discontinue HU. But treatment at optimal effective should be the primary goal of caregivers. [1]Smaldone A., Manwani D., Green NS, Greater number of perceived barriers to hydroxyurea associated with poorer health-related quality of life in youth with sickle cell disease, Pediatr Blood Cancer. 2019 [2] Steinberg MH, Voskaridou E, Kutlar A, Loukopoulos D, Koshy M, et al. (2003). Concordant fetal hemoglobin response to hydroxyurea in siblings with sickle cell disease. Am J Hematol 72: 121-126 [3] Ware RE, Despotovic JM, Mortier NA, Flanagan JM, He J, et al. (2011) Pharmacokinetics, pharmacodynamics, and pharmacogenetics of hydroxyurea treatment for children with sickle cell anemia. Blood 118: 4985-4991 Disclosures Galactéros: Addmedica: Membership on an entity's Board of Directors or advisory committees. Voskaridou:Celgene Corporation: Consultancy, Research Funding; Protagonist: Research Funding; Genesis: Consultancy, Research Funding; Acceleron: Consultancy, Research Funding; Addmedica: Membership on an entity's Board of Directors or advisory committees. Cannas:Addmedica: Membership on an entity's Board of Directors or advisory committees.

The severity of β-thalassemia intermedia (β-TI) is correlated to the degree of imbalanced globin chain synthesis. Phenotypic diversity of β-thalassemia (β-thal) depends on this imbalance, which ref...

Introduction La drepanocytose s’accompagne frequemment d’une acidose metabolique, dont le mecanisme n’est pas completement elucide. Methodes Dans cette etude prospective monocentrique, 25 patients drepanocytaires ayant un DFG estime par CKD-EPI (DFGe) > 60 ml/min/1,73m2 ont eu un test d’acidification urinaire par administration de furosemide (qui augmente le flux de sodium dans le tube distal, necessaire a la secretion d’H + ) et de fludrocortisone (qui augmente la reabsorption de sodium par la cellule principale, favorisant ainsi la secretion d’H+ par la cellule intercalaire α). Les urines sont ensuite recueillies toutes les heures pendant 4 heures. Un defaut d’acidification des urines est retenu si le pH urinaire reste superieur a 5,3 ou si l’ammoniurie reste inferieure a 33mEq/min. Resultats obtenus ou attendus Parmi les 25 patients ayant ete explores (36 ans [24–43], 17 femmes), 13 avaient une reponse anormale. Parmi ces patients, l’aldosteronemie etait normale, rendant peu probable le diagnostic d’acidose tubulaire de type 4. Neuf patients sur 13 avaient une bicarbonatemie basale normale. En comparaison aux patients ayant une reponse normale, les patients avec reponse anormale etaient significativement plus âges, plus frequemment traites par du bicarbonate de sodium, avait une uricemie plus elevee, une activite hemolytique plus importante, un DFGe plus bas, une excretion nette d’acide plus basse et une osmolarite urinaire sur echantillon plus basse. Une osmolarite urinaire sur echantillon inferieure a 391 mOsm/kgH2O avait une valeur predictive positive de 100 %, et permettait donc de predire avec une probabilite de 100 % une reponse anormale au test en-dessous de ce seuil. Une osmolarite urinaire en-dessous de 449 mOsm/kgH2O avait une valeur predictive negative de 100 %, et permettait donc de predire avec une probabilite de 100 % une reponse normale au test au-dessus de ce seuil. Conclusion Cette etude suggere que l’osmolarite urinaire sur echantillon permet de depister l’acidose tubulaire chez les patients drepanocytaires.

Introduction Du fait de l’anemie chronique, de l’hypogonadisme hypogonadotrope et des traitements chelateurs du fer, la grossesse reste de nos jours un defi chez les patientes presentant une beta-thalassemie homozygote ou heterozygote composite. Materiels et methodes Nous decrivons dans cette etude le deroulement des grossesses et la prise en charge de la beta-thalassemie, entre 1995 et 2015, chez des patientes suivies dans le registre national des thalassemies pour une beta-thalassemie majeure ou une beta-thalassemie intermediaire, transfusion–dependantes pendant la grossesse. Nous comparons dans un second temps ces patientes a un groupe de patientes non atteintes puis effectuons, pour finir une revue de la litterature recensant, les cas de grossesses au cours de la beta-thalassemie. Resultats Durant cette periode de 20 ans, 79 grossesses dont 16 fausses couches precoces ont ete recensees chez 37 patientes. Cinquante-six grossesses ont pu etre etudiees. Parmi elles, 5 grossesses etaient des grossesses gemellaires. Le recours a la procreation medicalement assistee a ete necessaire pour 16 % des grossesses. Le terme moyen a l’accouchement etait de 37,7 semaines d’amenorrhee et le poids moyen a la naissance etait de 2,760 g. Une cesarienne a ete necessaire dans 53,6 % des cas. Durant la grossesse, 6 evenements thromboemboliques, 6 infections severes, 6 cas d’hypertension gravidique, 6 retards de croissance intra-uterins, 3 cas d’alloimmunisation, 2 complications cardiaques (independantes de la surcharge en fer) et 1 preeclampsie ont ete retrouves. Le traitement chelateur du fer a ete arrete au debut de chaque grossesse excepte pour une, menee sous Deferoxamine. Les patientes beta-thalassemiques majeures ont ete plus transfusees pendant la grossesse que precedemment. Durant le postpartum, aucune complication majeure n’a ete retrouvee, si ce n’est 5 cas d’infections. Lors de la comparaison de ces patientes avec le groupe de patientes controles, le recours a la procreation medicalement assistee et le taux de cesariennes etaient plus importants chez les patientes beta-thalassemiques. Le poids de naissance etait plus petit, malgre un terme a l’accouchement similaire entre les 2 groupes. Les complications thromboemboliques, l’apparition d’hypertension gravidique, l’hemorragie de la delivrance et le retard de croissance intra-uterin etaient plus frequemment retrouves chez les patientes beta-thalassemiques. Concernant la periode du post-partum, il n’y avait pas de difference en termes de complications globales entre les 2 groupes, en dehors des infections, plus frequemment retrouvees chez les patientes beta-thalassemiques. Conclusion La grossesse parait sans danger chez les patientes beta-thalassemiques transfusees, avec peu de complications obstetricales et aucune complication liee a la surcharge en fer, notamment cardiaque. Ces patientes accouchent globalement a terme, mais le poids de naissance de ces bebes semble plus petit que dans la population generale.

Background and Purpose— There is little evidence about characteristics of ischemic stroke (IS) occurring in adults with sickle-cell disease (SCD). The objective of this study was to assess characteristics of first-ever IS in adults with SCD and to assess whether they differ from those occurring in child patients with SCD. Methods— Adult and child individuals with SCD who had a first-ever IS were identified from cohorts of patients followed up in an adult and a child sickle cell referral center. Mechanisms of IS were determined by consensus meeting from all available explorations using the following predefined classification: Vasculopathy, cardioembolism, other defined cause, and undetermined. Treatment and stroke recurrences were recorded from prospective follow-up performed in the referral centers. Results— Twenty-nine adults and 26 children had a first-ever IS; mean age (SD) was 7.1 (4.3) and 32.3 (11.6), respectively. With regard to IS mechanism, vasculopathy was less often the cause of IS in adults (12/29, 41%) than in children (24/26, 92%; P P log rank=0.046) despite exchange-blood transfusion in patients with vasculopathy. Conclusions— First-ever IS occurring in adults with SCD has specificities that justify further studies conducted in adults with SCD to improve understanding and management.

International audience; INTRODUCTION: The lung computed tomography (CT) features of acute chest syndrome (ACS) in sickle cell disease patients is not well described, and the diagnostic performance of bedside chest radiograph (CR) has not been tested. Our objectives were to describe CT features of ACS and evaluate the reproducibility and diagnostic performance of bedside CR. METHODS: We screened 127 consecutive patients during 166 ACS episodes and 145 CT scans (in 118 consecutive patients) were included in the study. RESULTS: Among the 145 CT scans, 139 (96%) exhibited a new pulmonary opacity and 84 (58%) exhibited at least one complete lung segment consolidation. Consolidations were predominant as compared with ground-glass opacities and atelectasis. Lung parenchyma was increasingly consolidated from apex to base; the right and left inferior lobes were almost always involved in patients with a new complete lung segment consolidation on CT scan (98% and 95% of cases, respectively). Patients with a new complete lung segment consolidation on CT scan had a more severe presentation and course as compared with others. The sensitivity of bedside CR for the diagnosis of ACS using CT as a reference was good (>85%), whereas the specificity was weak (

Key points Recent hemodynamic studies performed in large cohorts of adult patients with sickle cell disease have established the prevalence of pulmonary hypertension in this disease about 6 to 10%. Over half of these correspond to postcapillary pulmonary hypertension. Precapilliary arterial pulmonary hypertension seems to be a relatively infrequent complication of the disease. It is characterized by a different hemodynamic profile of idiopathic PAH with lower levels of pulmonary pressures and pulmonary vascular resistance. However, pulmonary vascular disease appears to have a significant impact on the functional status and vital prognosis of patients with sickle cell disease. The predictive value of echocardiography to detect pulmonary hypertension in this population is low (25–32%) when the threshold of tricuspid regurgitation velocity of 2.5 m/s is used. At present, no specific treatments for pulmonary arterial hypertension is currently approved for the treatment of PAH associated with sickle cell disease due to lack of data in this specific population.

Background: Little is known about the rate of, and factors affecting, progression of talar osteonecrosis related to sickle cell disease. Adult patients with sickle cell disease who presented with hip osteonecrosis were evaluated for talar osteonecrosis with radiographs and magnetic resonance imaging (MRI). Forty-five of them (75 tali) were diagnosed with talar osteonecrosis, and this group was evaluated for factors influencing the progression of the disease. Methods: Forty-five patients with sickle cell disease and osteonecrosis of the talus were identified with radiographs and MRI between 1985 and 1995. Seven of these patients were homozygous for hemoglobin S (S/S genotype), 26 had hemoglobin S/hemoglobin C, and 12 had hemoglobin S/beta-thalassemia. The talar osteonecrosis was graded with radiographs and MRI. The patients were followed with clinical examination and radiographs every 6 months until talar collapse and every year after the collapse. Results: The osteonecrosis was unilateral in 15 patients and bilateral in 30 at the time of the initial examination. Forty-five ankles were asymptomatic and 30 were symptomatic at the initial evaluation. MRI performed at the time of the most recent follow-up, and compared with MRI performed at diagnosis, did not show partial or total regression of the osteonecrosis in any of the patients, even those with asymptomatic stage-I osteonecrosis. At the time of the most recent follow-up (mean, 20 years; range, 15 to 25 years), pain and collapse had developed in all except 12 ankles. The stage of the osteonecrosis at the initial visit, pain, the genotype of the sickle cell disease, and the extent and location of the lesion in the talus were risk factors for progression of the disease. Conclusions: In the majority of the patients with sickle cell disease, osteonecrosis of the talus should be expected to show relevant clinical and radiographic evidence of progression over a long period. Level of Evidence: Prospective Level II. See Instructions for Authors for a complete description of levels of evidence.

Background Our understanding of the pathophysiologic processes underlying sickle cell nephropathy remains incomplete. We performed a pilot study to investigate the potential value of magnetic resonance imaging (MRI) for the assessment of kidney oxygenation and detection of potential changes to tissue perfusion and cellular integrity during a vaso-occlusive crisis. Study Design A case-control study. Setting & Participants 10 homozygous patients with sickle cell disease (SCD), without kidney disease (based on estimated glomerular filtration rate and albuminuria), underwent renal MRI during a vaso-occlusive crisis episode. The imaging data obtained were compared with those for a second MRI performed at steady state (median, 56 [IQR, 37-72] days after the vaso-occlusive crisis MRI). The control group consisted of 10 apparently healthy individuals. Measurements Deoxyhemoglobin level assessed by R2* value was calculated using the blood oxygen level−dependent technique. The intravoxel incoherent motion diffusion-weighted imaging technique was used to calculate D, D*, and F parameters. Results Median medullary R2* values on steady-state MRI were significantly higher for patients with SCD than for controls ( P =0.01) and did not change significantly during the vaso-occlusive crisis. No significant differences in median cortical R2* values were observed. Both cellular integrity (D) and local perfusion (D* and F) were significantly altered in medullary and cortical areas during vaso-occlusive crises in comparison to steady state in patients with SCD. These parameters did not differ significantly between patients with SCD assessed at steady state and the control group. Limitations Small sample size, estimation of glomerular filtration rate according to CKD-EPI creatinine equation without adjustment for race. Conclusions Deoxyhemoglobin levels in the medullary area are higher in patients with SCD, during vaso-occlusive crises and at steady state, than in controls. Alterations to the tissue perfusion and cellular integrity of renal parenchyma are a common finding during vaso-occlusive crises that provide additional evidence that a vaso-occlusive crisis may be associated with subclinical kidney injury detectable on MRI.

Sickle-cell disease (SCD), one of the most common severe monogenic disorders into the world, is associated with an increased frequency of chronic kidney disease. SCD is caused by a point mutation in the gene encoding β globin gene which leads to the formation of hemoglobin S that polymerises after deoxygenation. HbS polymerisation is associated with erythrocyte rigidity and vaso-occlusive episodes that play a central role into SCD pathogenesis. The spectrum of renal diseases during SCD is broad and includes various renal manifestations which become more apparent with increasing age. Underlying pathophysiological processes involved in sickle cell nephropathy are multifactorial but endothelial dysfunction related to chronic hemolysis is a key factor contributing to renal involvement. Our review focuses on the pathogenesis and on the spectrum of renal manifestations occurring in SCD patients.

This review provides an overview of the clinical management of sickle-cell disease (SCD) with recently published findings.Unfortunately, negative observations did not confirm the hope that therapies acting on nitric oxide-cyclic GMP signaling, NSAIDs or Gardos channel inhibitor would control SCD vaso-occlusive crises. The safety of hydroxycarbamide was further supported by two observational studies covering 20 years and over 2 years in young children. Concerning the management of chronic visceral complications of SCD, the STOP II trial showed the risk of discontinuing blood exchange transfusion for children with transcranial Doppler-assessed accelerated blood-flow velocities. The French multicenter Etendard study found that only 25% of SCD patients with tricuspid regurgitation velocity (TRV) 2.5 m/s or more on echocardiograms had catheterization-confirmed pulmonary hypertension. However, elevated TRV, regardless of its cause, was associated with higher mortality. Finally, recent results identified new therapeutic strategies for the treatment and prevention of renal dysfunction, priapism and skin ulcers, but prospective studies are needed to confirm those findings.SCD treatment relies on concomitant preventive and curative measures to control its acute and chronic manifestations. Pathophysiologic advances have enabled better management, with new therapeutics highly likely in the near future.

Abnormal blood flow accounts for most of the clinical morbidity of sickle cell disease (SCD) [1,2]. Most notably, occlusion of flow in the microvasculature causes the acute pain crises [3] that are the commonest cause for patients with SCD to seek medical attention [4] and major determinants of their quality of life [5]. Based on evidence that endothelial P-selectin is central to the abnormal blood flow in SCD we provide results from four of our studies that are germane to microvascular blood flow in SCD. A proof-of-principle study established that doses of heparin lower than what are used for anticoagulation but sufficient to block P-selectin improved microvascular blood flow inpatients with SCD. An in vitro study showed that Pentosan Polysulfate Sodium (PPS) had greater P-selectin blocking activity than heparin. A Phase I clinical study demonstrated that a single oral dose of PPS increased microvascular blood flow in patients with SCD. A Phase II clinical study that was not completed documented that daily oral doses of PPS administered for 8 weeks lowered plasma levels of sVCAM-1 and tended to improve microvascular blood flow in patients with SCD. These data support the concept that P-selectin on the microvascular endothelium is critical to both acute vascular occlusion and chronically impaired microvascular blood flow in SCD. They also demonstrate that oral PPS is beneficial to microvascular sickle cell blood flow and has potential as an efficacious agent for long-term prophylactic therapy of SCD.

Sickle-cell disease (SCD), one of the most common severe monogenic disorders into the world, is associated with an increased frequency of chronic kidney disease. SCD is caused by a point mutation in the gene encoding β globin gene which leads to the formation of hemoglobin S that polymerises after deoxygenation. HbS polymerisation is associated with erythrocyte rigidity and vaso-occlusive episodes that play a central role into SCD pathogenesis. The spectrum of renal diseases during SCD is broad and includes various renal manifestations which become more apparent with increasing age. Underlying pathophysiological processes involved in sickle cell nephropathy are multifactorial but endothelial dysfunction related to chronic hemolysis is a key factor contributing to renal involvement. Our review focuses on the pathogenesis and on the spectrum of renal manifestations occurring in SCD patients.

The pathophysiology of acute chest syndrome (ACS) in patients with sickle cell disease is complex, and pulmonary artery thrombosis (PT) may contribute to this complication.To evaluate the prevalence of PT during ACS using multidetector computed tomography (MDCT).We screened 125 consecutive patients during 144 ACS episodes. One hundred twenty-one MDCTs (in 103 consecutive patients) were included in the study.Twenty MDCTs were positive for PT, determining a prevalence of 17% (95% confidence interval, 10-23%). Revised Geneva clinical probability score was similar between patients with PT and those without. D-dimer testing was very often positive (95%) during ACS. A precipitating factor for ACS was less frequently found in patients with PT as compared with those without. Patients with PT exhibited significantly higher platelet counts (517 [273-729] vs. 307 [228-412] 10(9)/L, P0.01) and lower bilirubin (28 [19-43] vs. 44 [31-71] μmol/L, P0.01) levels at the onset of ACS as compared with others. In addition, patients with PT had a higher platelet count peak (537 [345-785] vs. 417 [330-555] 10(9)/L, P = 0.048) and smaller bilirubin peak (36 [18-51] vs. 46 [32-83] μmol/L, P = 0.048)and lactate dehydrogenase peak (357 [320-704] vs. 604 [442-788] IU/L, P = 0.01) during hospital stay as compared with others.PT is not a rare event in the context of ACS and seems more likely in patients with higher platelet counts and lower hemolytic rate during ACS. Patients with sickle cell disease presenting with respiratory symptoms suggestive of ACS may benefit from evaluation for PT.

Sickle cell disease is an autosomal genetic condition which represents the most frequent genetic disease in Ile-de-France and Caribbean islands. The main clinical manifestations can be divided into infectious disease, hemolytic anemia and vaso-occlusive events. Pulmonary complications represent 20 to 30% of mortality due to sickle cell and can be divided into acute and chronic events. Acute chest syndrome (ACS) is an acute lung injury often preceded by a vaso-occlusive crisis and triggered by different factors including: hypoventilation, pulmonary infectious disease and vascular occlusions. These occlusions can be secondary to fat embolism, thrombosis or sickling. Treatment is mainly supportive combining oxygen supplementation adequate hydration analgesia and sedation. Exchange transfusion may be indicated in severe forms of ACS, characterized by a right ventricular dysfunction and acute respiratory failure. Pulmonary hypertension is the most serious chronic complication. Its frequency is estimated at 6% in adult patients and is more often described in patients with venous ulcers and higher levels of chronic hemolysis. Prognosis is poor with 12.5% of patients dying in the first two years following diagnosis irrespective of the actual pulmonary artery pressure level. There are currently limited data on the effects of any treatment modality. Other respiratory complications such as sleep disorders and nocturnal hypoxemia, infiltrative lung disease and exertional dyspnea are described and should be considered.

M. Cazenave, V. Audard and J.P. Bertocchio, and P Bartolucci and M. Courbebaisse equally contributed to this work Introduction: Metabolic acidosis is encountered in 42% of patients with sickle cell disease (SCD) (Maurel S, Clin J Am Soc Nephrol, 2014) but the pathophysiological processes remain largely unknown. Patients and methods: We conducted a monocentric observational study including SCD patients, at steady state (>1 month of a vaso occlusive crisis and >3 months of a transfusion), with and without overt metabolic acidosis [HCO3-]60 ml/min/1.73 m2 The urinary acidification test was achieved by oral administration of furosemide and fludrocortisone, increasing distal tubular Na+ delivery, Na+ reabsorption via principal cells and H+ secretion via α-intercalated cells (Walsh SB, Kidney Int, 2007). An abnormal test was identified by a failure to lower urinary pH Results: We evaluated 13 SCD patients with metabolic acidosis (4 males, 40.0 years [33.0-44.0], eGFR=114.0 ml/min/1,73m2 [95.0-126.0]) and 12 SCD patients without overt metabolic acidosis (4 males, 29.5 years [24,0.0-37.3], eGFR=128.5 ml/min/1,73m2 [124.8-140.0]). During the test, among overt metabolic acidosis patients, urinary pH remained ≥5.3 in 7 patients and urinary NH4+ excretion remained Regarding hemolysis parameters, patients with overt metabolic acidosis had lower hemoglobin (7.7 [6.8-8.7] vs 9.2 [8.9-9.4] g/dl, p=0.02), higher lactate dehydrogenase (492 [455-636] vs 327 [256-458] IU/l, p=0.01) and a higher average red blood cell density (1.097 [1.096-1.097] vs 1.092 [1.091-1.094], p Discussion: Our study shows that SCD patients with overt metabolic acidosis have a defect in renal acidification process. The positive association between NH4+ excretion and fasting urine osmolality suggests that this metabolic acidosis is likely due to an impaired NH4+availability, probably secondary to the medullary ischemia seen in some SCD patients. This is supported by the fact that SCD patients with metabolic acidosis have a haematological phenotype of hyperhemolysis. Contrary to previous reports (Goossens JP, Clin Chim Act, 1972; Oster JR, Arch Intern Med, 1976), our results highlight that SCD patients with plasma bicarbonate within the normal range are not likely to exert incomplete tubular metabolic acidosis. Conclusion: In SCD patients, metabolic acidosis is related to a renal acidification defect, itself linked to the severity of hemolysis. Disclosures Bartolucci: Addmedica: Research Funding; Novartis US: Membership on an entity's Board of Directors or advisory committees; GBT: Membership on an entity's Board of Directors or advisory committees; Fondation Fabre: Research Funding.