Search

Background Large β-globin gene cluster deletions (hereditary persistence of fetal hemoglobin [Hb] or β-, δβ-, γδβ-, and ϵγδβ-thalassemia), are associated with widely disparate phenotypes, including variable degrees of microcytic anemia and Hb F levels. When present, increased Hb A2 is used as a surrogate marker for β-thalassemia. Notably, ϵγδβ-thalassemias lack the essential regulatory locus control region (LCR) and cause severe transient perinatal anemia but normal newborn screen (NBS) results and Hb A2 levels. Herein, we report a novel deletion of the ϵ, Aγ, Gγ, and ψβ loci with intact LCR, δ-, and β-regions in 2 women and newborn twins. Methods Capillary electrophoresis (CE), high-performance liquid chromatography (HPLC), DNA sequencing, multiplex ligation-dependent probe amplification (MLPA), gap-polymerase chain reaction (gap-PCR), and long-read sequencing (LRS) were performed. Results NBS showed an Hb A > Hb F pattern for both twins. At 20 months, Hb A2 was increased similarly to that in the mother and an unrelated woman. Unexplained microcytosis was absent and the twins lacked severe neonatal anemia. MLPA, LRS, and gap-PCR confirmed a 32 599 base pair deletion of ϵ (HBE1) through ψβ (HBBP1) loci. Conclusions This deletion represents a hemoglobinopathy category with a distinct phenotype that has not been previously described, an ϵγ-thalassemia. Both the NBS Hb A > F pattern and the subsequent increased Hb A2 without microcytosis are unusual. A similar deletion should be considered when this pattern is encountered and appropriate test methods selected for detection. Knowledge of the clinical impact of this new category will improve genetic counselling, with distinction from the severe transient anemia associated with ϵγδβ-thalassemia.

We describe presenting features, treatment strategies, and follow-up events involving 41 patients (median age 39 years, range 1-81; 54% males) with high oxygen affinity (HOA) hemoglobinopathy-associated erythrocytosis, seen at our institution (1973-2020). Thirty-four (83%) patients carried β-chain (13 Malmo, 4 Olympia, 3 San Diego, 2 Wood) and 7 (17%) α-chain (4 Dallas and one each Columbia-Missouri, Jackson, and Wayne) variants. Median (range) hemoglobin (Hgb)/hematocrit (Hct), serum erythropoietin and p50 were 18 g/dL/52.9% (16-21.9/48-66), 10.4 mIU (4-36.3), and 20 mmHg (12-25), respectively. Family history was documented in 24 patients and history of thrombosis in two (5%). Treatment included phlebotomy in 23 and antiplatelet therapy in 21 patients. At a median follow-up of 10 years, 23 (56%) patients reported one or more symptoms that were thought to be related to their increased Hct while thrombosis was documented in 10 (24%) patients. Neither Hgb/Hct level nor active phlebotomy showed a significant correlation with either thrombotic or nonthrombotic symptoms (p > .1 in all instances). Among 23 pregnancies recorded, 78% resulted in live births and no fetal loss was attributed to erythrocytosis. The current study does not implicate Hgb/Hct level as a major contributor of morbidity in HOA hemoglobinopathy-associated erythrocytosis and suggests limited therapeutic value for phlebotomy.

The objective of this study is to describe the clinical features and outcomes of patients with the newly defined vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic (VEXAS) syndrome. Nine men with somatic mutations in the UBA1 gene were identified; the most frequent variant was p.Met41Thr (7 of 9, 78%). The median age at VEXAS diagnosis was 74 (67, 76.5) years, and patients had a median duration of symptoms for 4 years before diagnosis. Refractory constitutional symptoms (88%), ear and nose chondritis (55%), and inflammatory arthritis (55%) were common clinical features. Vasculitis was noted in 44%. All patients had significantly elevated inflammatory markers and macrocytic anemia. Thrombocytopenia was present in 66% at diagnosis of VEXAS. Eight patients had bone marrow biopsies performed. All bone marrows were hypercellular, and there was vacuolization of the erythroid (100%) or myeloid precursors (75%). Glucocorticoids attenuated symptoms at prednisone doses ≥20 mg per day, but no other immunosuppressive agent showed consistent long-term control of disease. One patient with coexisting plasma-cell myeloma received plasma-cell-directed therapy with improvement of the inflammatory response, which is a novel finding. In conclusion, VEXAS syndrome is a clinically heterogeneous, treatment-refractory inflammatory condition caused by somatic mutation of the UBA1 gene. Patients often present with overlapping rheumatologic manifestations and persistent hematologic abnormalities. As such, internists and subspecialists, including pathologists, should be aware of this condition to avert diagnostic delay, now that the etiology of this syndrome is known.

The presence of increased multinucleated megakaryocytes (aka osteoclast-like) is considered a dysplastic feature in myelodysplastic syndrome; however, its clinical significance in isolation is uncertain. Herein, we report the clinicopathologic and genetic features of 18 such cases of 40,539 bone marrow biopsies spanning 10 years. All 18 patients had ≥25% multinucleated megakaryocytes in otherwise normal bone marrow biopsies, which were evaluated for plasma cell neoplasms (n=9), lymphoma (n=4), or anemia/neutropenia (n=5). None of the 17 patients tested showed acquired cytogenetic abnormalities. Sixteen patients underwent targeted gene panel next-generation sequencing: 9 patients had no pathogenic mutations; 3 harbored a single pathogenic mutation with variant allele frequencies of 7.5%, 7.6%, and 10.7%, likely representing clonal hematopoiesis of indeterminate potential; 1 had 2 pathogenic mutations, 1 of which had a variant allele frequency >20%. Fourteen of 18 patients had a follow-up period >6 months (median: 36.5 mo, range: 7 to 110 mo) and no patients developed a new-onset cytopenia, a progressive cytopenia, or a myeloid neoplasm. The patient with 2 mutations had persistent anemia, worrisome for an emerging MDS. However, given the absence of thrombocytopenia, increased multinucleated megakaryocytes in this patient could be an unrelated incidental finding. Our study indicates that increased multinucleated megakaryocytes as an isolated finding is a rare phenomenon, and this sole morphologic finding is not diagnostic of myelodysplastic syndrome. Diagnostic approaches in the presence of increased multinucleated megakaryocytes are proposed based on different clinical and pathologic scenarios.

Objectives SF3B1 mutations are the most common mutations in myelodysplastic syndromes (MDS). The International Working Group for the Prognosis of MDS (IWG-PM) recently proposed SF3B1-mutant MDS (SF3B1-mut-MDS) as a distinct disease subtype. We evaluated the spectrum and molecular landscape of SF3B1-mutated myeloid disorders and assessed the prognostication in MDS harboring SF3B1 mutations (MDS-SF3B1). Methods Cases were selected by retrospective review. Clinical course and laboratory and clinical findings were collected by chart review. SF3B1-mut-MDS was classified following IWG-PM criteria. Results SF3B1 mutations were identified in 75 of 955 patients, encompassing a full spectrum of myeloid disorders. In MDS-SF3B1, Revised International Prognostic Scoring System (IPSS-R) score greater than 3 and transcription factor (TF) comutations were adverse prognostic markers by both univariate and multivariate analyses. We confirmed the favorable outcome of IWG-PM-defined SF3B1-mut-MDS. Interestingly, it did not show sharp prognostic differentiation within MDS-SF3B1. Conclusions SF3B1 mutations occur in the full spectrum of myeloid disorders. We independently validated the favorable prognostication of IWG-PM-defined SF3B1-mut-MDS. However it may not provide sharp prognostication within MDS-SF3B1 where IPSS-R and TF comutations were prognostic-informative. Larger cohort studies are warranted to verify these findings and refine MDS-SF3B1 prognostication.

Background Hemolytic disease of the fetus and newborn (HDFN) attributable to anti-M is rare, although case reports implicate anti-M in varying severities of HDFN, including fetal hydrops and intrauterine death. Case description We describe the case of a newborn with HDFN associated with an atypical immunoglobulin (Ig) G anti-M that reacted best at cold temperatures. The maternal antibody detected in pregnancy was not reactive at 37°C, and a direct antiglobulin test (DAT) on red blood cells (RBCs) from the newborn was negative, suggesting an anti-M that should not have been clinically relevant. However, the infant developed hyperbilirubinemia (bilirubin level, 17.6 mg/dL), hemolytic anemia (hemoglobin nadir, 5.5 g/dL), and reticulocytopenia. Laboratory testing demonstrated the presence of an IgG anti-M in maternal and neonatal samples reacting best at 4°C. This passively acquired IgG anti-M provoked hemolytic anemia in the infant and likely suppressed erythropoiesis, resulting in reticulocytopenia with prolonged anemia. He was treated for IgG anti-M HDFN with 10 intravenous Ig infusions and 10 days of oral prednisone followed by a taper. He required seven transfusions with M- RBCs. His hemoglobin level normalized at 3 months of age. Follow-up at 2 years revealed no hematologic or neuro-developmental concerns. Conclusion To our knowledge, this is the second report of HDFN attributable to an IgG anti-M reacting preferentially at cold temperature with no 37°C reactivity. Clinically relevant IgG anti-M may elude standard testing. Early recognition and testing for cold-reacting IgG anti-M should be considered for newborns with hemolysis, a negative DAT, and prolonged anemia.

Hb Bronovo [α103(G10)His→Leu, HBA2: c.311A>T] is an α-globin variant that interferes with and decreases binding efficiency to α hemoglobin (Hb) stabilizing protein (AHSP), a chaperone molecule. The...

FLT3-internal tandem duplication occurs in 20–30% of acute myeloid leukemia and confers an adverse prognosis with its allelic ratio being a key risk stratifier. The US Food and Drug Administration recently approved FLT3 inhibitors midostaurin and gilteritinib in FLT3 mutation-positive acute myeloid leukemia. Historically, FLT3 was tested by fragment analysis, which has become the standard method endorsed by international guidelines. However, next generation sequencing is increasingly used at acute myeloid leukemia diagnosis given its ability to simultaneously evaluate multiple clinically informative markers. As FLT3-internal tandem duplication detection was known to be challenging by next generation sequencing and the results carry profound prognostic and therapeutic implications, it is important to thoroughly examine its performance in FLT3-internal tandem duplication detection and allelic ratio classification. In a comparative study with fragment analysis, we retrospectively reviewed our experience using a custom-designed, hybridization capture-based, targeted next generation sequencing panel. Among 7902 cases, FLT3-internal tandem duplication was detected in 335 with variable sizes (3–231 bp) and insertion sites. Fragment analysis was also performed in 402 cases, demonstrating 100% concordance in FLT3-internal tandem duplication detection. In 136 dual-tested, positive cases, 128/136 (94%) exhibited concordant high/low allelic ratio classifications. The remaining 6% showed borderline low allelic ratio by next generation sequencing. The two methods were concordant in FLT3-tyrosine kinase domain mutation detection at the hotspot D835/I836 targeted by fragment analysis. Furthermore, seven mutations which may benefit from FLT3 inhibitor therapy were detected by next generation sequencing, in regions not covered by fragment analysis. Our study demonstrates that using a hybridization capture-based chemistry and optimized bioinformatics pipeline, next generation sequencing can reliably detect FLT3-internal tandem duplication and classify its allelic ratio for acute myeloid leukemia risk stratification. Next generation sequencing also exhibits superior comprehensiveness in FLT3 mutation detection and may further improve personalized, targeted therapy in acute myeloid leukemia.

KEY POINTS Theoretical models suggest there is no benefit of high affinity haemoglobin to preserve maximal oxygen uptake in acute hypoxia but the comparative biology literature has many examples of species that are evolutionarily adapted to hypoxia and have high affinity haemoglobin. We studied humans with high affinity haemoglobin and compensatory polycythaemia. These subjects performed maximal exercise tests in normoxia and hypoxia to determine how their altered haemoglobin affinity impacts hypoxic exercise tolerance. The high affinity haemoglobin participants demonstrated an attenuated decline in maximal aerobic capacity in acute hypoxia. Those with high affinity haemoglobin had no worsening of pulmonary gas exchange during hypoxic exercise but had greater lactate and lower pH than controls for all exercise bouts. High affinity haemoglobin and compensatory polycythaemia mitigated the decline in exercise performance in acute hypoxia through a higher arterial oxygen content and an unchanged pulmonary gas exchange. ABSTRACT The longstanding dogma is that humans exhibit an acute reduction in haemoglobin (Hb) binding affinity for oxygen that facilitates adaptation to moderate hypoxia. However, many animals have adapted to high altitude through enhanced Hb binding affinity for oxygen. The objective of the study was to determine whether high affinity haemoglobin (HAH) affects maximal and submaximal exercise capacity. To accomplish this, we recruited individuals (n = 11, n = 8 females) with HAH (P50 = 16 ± 1 mmHg), had them perform normoxic and acute hypoxic (15% inspired oxygen) maximal exercise tests, and then compared their results to matched controls (P50 = 26 ± 1, n = 14, n = 8 females). Cardiorespiratory and arterial blood gases were collected throughout both exercise tests. Despite no difference in end-exercise arterial oxygen tension in hypoxia (59 ± 6 vs. 59 ± 9 mmHg for controls and HAH, respectively), the HAH subjects' oxyhaemoglobin saturation ( Sa,O2 ) was ∼7% higher. Those with HAH had an attenuated decline in maximal oxygen uptake ( VO2max ) (4 ± 5% vs. 12 ± %, p

Pulse oximetry is routinely used in the newborn nursery for clinical monitoring and to detect critical congenital heart disease. The differential diagnoses for reduced peripheral oxygen saturation in an infant include congenital heart disease, respiratory distress syndrome, transient tachypnea of the newborn, persistent pulmonary hypertension of the newborn, meconium aspiration syndrome, pneumonia, pneumothorax, and sepsis. The diagnostic evaluation for neonatal hypoxemia can be invasive and expensive. When this evaluation is unrevealing, other interventions may be tried without clear benefit to the patient, including, but not limited to, supplemental oxygen. Therefore, it is important to consider alternative, albeit rare, diagnoses, including hemoglobinopathies with abnormal oxygen binding properties. Mutations in the structure of alpha- and beta-globin chains can alter the affinity of hemoglobin for oxygen, and changes in oxygen affinity may result in changes in the oxygen saturation detected by pulse oximetry. These changes may or may not be of clinical significance. This case report describes Hemoglobin Sunshine Seth, a rare low-oxygen-affinity hemoglobin variant presenting as reduced peripheral oxygen saturation in an otherwise well-appearing infant male.

Secondary acquisition of t(9;22)(q34;q11.2)/BCR-ABL1 fusion in the context of de novo acute myeloid leukemia (AML) with inv(3)(q21q26)/GATA2-MECOM rearrangement has been rarely reported. Furthermore, t(2;11)(p23;q23)/KMT2A-ASXL2 fusion has been rarely described with only a single case reported to date. We report a 45-year-old male with a diagnosis of de novo AML harboring GATA2-MECOM rearrangement in conjunction with a related subclone with concomitant inv(3) and t(9;22). The patient was treated with a tyrosine kinase inhibitor (TKI) which lead to disappearance of the inv(3)/t(9;22) subclone and subsequent expansion of the inv(3) ancestral clone. The patient was started on a 7+3 induction regimen with TKI but had persistent disease. He was placed on several additional treatment protocols and only achieved morphologic remission with a combination of fludarabine, cytarabine and filgrastim with TKI. Approximately 11.5 months after diagnosis the patient relapsed with the inv(3) clone predominating initially, followed by return of the inv(3)/t(9;22) subclone and the emergence of a second subclone with concomitant inv(3) and t(2;11)(p23;q23). Mate-pair sequencing was performed and identified a KMT2A-ASXL2 in-frame fusion, which was only recently described in a single case of therapy-related AML. For BCR-ABL1 positive AML, which generally carries a poor prognosis, treatment with TKIs has been proposed in combination with standard chemotherapy. In our case, treatment with TKI alone led to initial response of the BCR-ABL1 positive clone, but the ancestral clone quickly expanded and subsequent standard AML therapy may have led to further clonal evolution and re-emergence of the BCR-ABL1 clone in the absence of therapeutic selection.

Background Loss of function mutations in the EGLN1 gene are a cause of erythrocytosis. EGLN1 encodes for prolyl hydroxylase domain protein 2 (PHD2). PHD2 hydroxylates and downregulates hypoxia-inducible factor-2α (HIF-2α), a transcription factor that regulates erythropoiesis. While the large majority of erythrocytosis-associated EGLN1 mutations occur within its catalytic domain, rare mutations reside in its zinc finger. This zinc finger binds a Pro-Xaa-Leu-Glu motif in p23, an HSP90 cochaperone that facilitates hydroxylation of HIF-α, an HSP90 client. Essentially nothing is known about the specific interactions between the PHD2 zinc finger and p23. Results Here, we characterize an erythrocytosis-associated mutation in the zinc finger, K55N, that abolishes interaction with p23. We provide evidence that the affected residue, Lys-55, interacts with Asp-152 of p23. We also present results that indicate that PHD2 Arg-32 interacts with p23 Glu-160. Conclusion These studies not only reinforce the importance of the PHD2 zinc finger in the control of erythropoiesis, but also lead to a model in which a peptide motif in p23 binds in a specific orientation to a predicted groove in the zinc finger of PHD2.

Arterial oxygen tension and oxyhemoglobin saturation ([Formula: see text]) decrease in parallel during hypoxia. Distinguishing between changes in oxygen tension and oxygen content as the relevant physiological stimulus for cardiorespiratory alterations remains challenging. To overcome this, we recruited nine individuals with hemoglobinopathy manifesting as high-affinity hemoglobin [HAH; partial pressure at 50% [Formula: see text] (P50) = 16 ± 0.4 mmHg] causing greater [Formula: see text] at a given oxygen partial pressure compared with control subjects ( n = 12, P50 = 26 ± 0.4 mmHg). We assessed ventilatory and cardiovascular responses to acute isocapnic hypoxia, iso-oxic hypercapnia, and 20 min of isocapnic hypoxia (arterial Po2 = 50 mmHg). Blood gas alterations were achieved with dynamic end-tidal forcing. When expressed as a function of the logarithm of oxygen partial pressure, ventilatory sensitivity to hypoxia was not different between groups. However, there was a significant difference when expressed as a function of [Formula: see text]. Conversely, the rise in heart rate was blunted in HAH subjects when expressed as a function of partial pressure but similar when expressed as a function of [Formula: see text]. Ventilatory sensitivity to hypercapnia was not different between groups. During sustained isocapnic hypoxia, the rise in minute ventilation was similar between groups; however, heart rate was significantly greater in the controls during 3 to 9 min of exposure. Our results support the notion that oxygen tension, not content, alters cellular Po2in the chemosensors and drives the hypoxic ventilatory response. Our study suggests that in addition to oxygen partial pressure, oxygen content may also influence the heart rate response to hypoxia.NEW & NOTEWORTHY We dissociated the effects of oxygen content and pressure of cardiorespiratory regulation studying individuals with high-affinity hemoglobin (HAH). During hypoxia, the ventilatory response, expressed as a function of oxygen tension, was similar between HAH variants and controls; however, the rise in heart rate was blunted in the variants. Our work supports the notion that the hypoxic ventilatory response is regulated by oxygen tension, whereas cardiovascular regulation may be influenced by arterial oxygen content and tension.

Patients with large granular lymphocytic leukemia (LGLL) frequently present with neutropenia. When present, anemia is usually accompanied by neutropenia and/or thrombocytopenia and isolated anemia is uncommon. We evaluated a cohort of 244 LGLL patients spanning 15 years and herein report the clinicopathologic features of 34 (14%) with isolated anemia. The patients with isolated anemia showed a significantly male predominance (p = 0.001), a lower level of hemoglobulin (p 0.0001) and higher MCV (p = 0.017) and were less likely to have rheumatoid arthritis (p = 0.023) compared to the remaining 210 patients. Of the 34 LGLL patients with isolated anemia, 13 (38%) presented with pure red cell aplasia (PRCA), markedly decreased reticulocyte count and erythroid precursors, and more transfusion-dependence when compared to non-PRCA patients. There was no other significant clinicopathologic difference between PRCA and non-PRCA patients. 32 patients were followed for a median duration of 51 months (6-199). 24 patients were treated (11/11 PRCA and 13/21 non-PRCA patients, p 0.02). The overall response rate to first-line therapy was 83% [8/11 (72.7%) for PRCA, 12/13 (92.3%) for non-PRCA], including 14 showing complete response and 6 showing partial response with a median response duration of 48 months (12-129). Half of non-PRCA patients who were observed experienced progressive anemia. During follow-up, no patients developed neutropenia; however, 5/27 (18.5%) patients developed thrombocytopenia. No significant difference in overall survival was noted between PRCA and non-PRCA patients. In summary, this study demonstrates the unique features of LGLL with isolated anemia and underscores the importance of recognizing LGLL as a potential cause of isolated anemia, which may benefit from disease-specific treatment. LGLL patients with PRCA were more likely to require treatment but demonstrated similar clinicopathologic features, therapeutic responses, and overall survival compared to isolated anemia without PRCA, suggesting PRCA and non-PRCA of T-LGLL belong to a common disease spectrum.

Germline predisposition syndromes (GPS) result from constitutional aberrations in tumor suppressive and homeostatic genes, increasing risk for neoplasia in affected kindred. In this study, we present clinical and genomic data on 144 Mayo Clinic patients with GPS; 59 evaluated prospectively using an algorithm-based diagnostic approach in the setting of a dedicated GPS/ inherited bone marrow failure syndrome (IBMFS) clinic. Seventy-two (50%) patients had IBMFS (telomere biology disorders-32,Fanconi anemia-18, Diamon Blackfan Anemia - 11, congenital neutropenia-5, Schwachman-Diamond Syndrome-5 and Bloom Syndrome-1), 27 (19%) had GPS with antecedent thrombocytopenia (RUNX1-FPD-15, ANKRD26-6, ETV6-2, GATA1-1, MPL-3), 28 (19%) had GPS without antecedent thrombocytopenia (GATA2 haploinsufficiency-16, DDX41-10, CBL-1 and CEBPA-1) and 17 (12%) had general cancer predisposition syndromes (ataxia telangiectasia-7, heterozygous ATM variants-3, CHEK2-2, TP53-2, CDK2NA-1, NF1-1 and Nijmegen Breakage Syndrome-1). Homozygous and heterozygous ATM pathogenic variants were exclusively associated with lymphoproliferative disorders (LPD), while DDX41 GPS was associated with LPD and myeloid neoplasms. The use of somatic NGS-testing identified clonal evolution in GPS patients, with ASXL1, RAS pathway genes, SRSF2 and TET2 being most frequently mutated. Fifty-two (91%) of 59 prospectively identified GPS patients had a change in their management approach, including additional GPS-related screening in 42 (71%), referral for allogenic HSCT workup and screening of related donors in 16 (27%), medication initiation and selection of specific conditioning regimens in 14 (24%), and genetic counseling with specific intent of fertility preservation and preconceptual counselling in 10 (17%) patients; highlighting the importance of dedicated GPS screening, detection and management programs for patients with hematological neoplasms. This article is protected by copyright. All rights reserved.

Background Sickle cell disease is a homozygous hemoglobinopathy with vaso-occlusive complications secondary to abnormal sickling of red blood cells under stressful conditions such as hypoxia. Children with sickle cell trait have a heterozygous genetic state, typically without symptoms. Observation An 8-year-old boy diagnosed with sickle cell trait was found to have multiple complications consistent with sickle cell disease, including pain crises, osteomyelitis, and priapism. Over a 6-year period, he underwent routine laboratory evaluations without a definitive diagnosis. The diagnosis of a compound heterozygous state of hemoglobin S/hemoglobin Quebec-Chori was eventually made on the basis of mass spectrometry and confirmed with hemoglobin subunit beta gene sequencing. Conclusion Expanding diagnostic evaluation in patients with abnormal clinical presentations is vital to making the correct diagnosis and hence earlier institution of appropriate management of rare hemoglobinopathies.

A novel unstable Gγ-globin variant, Hb F-Wentzville [Gγ24(B6)Gly→Glu; HBG2: c.74G>A, (p.Gly25Glu)], was identified in a young infant who required a single transfusion of erythrocytes for hemolytic anemia. This is the first reported γ-globin variant affecting the highly conserved glycine residue at helical position B6. In the tertiary structure of hemoglobin (Hb), glycine at B6 is in close proximity to another invariant glycine residue at E8. Prior studies have shown that replacement of the B6 or E8 glycine residues with bulkier amino acids disrupts packing between the B and E helices, resulting in Hb instability. Thus, Hb F-Wentzville is analogous to the following unstable β-globin B6 variants: Hb Savannah (HBB: c.74G>T, p.Gly24Val), Hb Riverdale-Bronx (HBB: c.73G>C, p.Gly24Arg), and Hb Moscva (HBB: c.74G>A, p.Gly24Asp).

Objective To describe the multifactorial etiologies of extreme thrombocytosis (EXT) in different care settings and the frequency of finding an occult malignancy. Patients and Methods We conducted a retrospective chart review at Mayo Clinic from January 1, 2011, through December 31, 2016. Adult patients who had at least 2 readings of platelet counts greater than 1000×109/L within 30 days of each other were included. We determined the causes of EXT on the basis of preset definitions of precipitating factors and identified the dominant causes on the basis of the trend of platelet counts. Results A total of 44,490 patients had thrombocytosis, and 305 patients (0.7%) had EXT. In 242 patients (79.3%), EXT was multifactorial. Surgical complications (54.1%) and hematologic malignancies (27.9%) were the 2 most dominant causes. Thirty-eight patients (12.5%) had new diagnoses of malignancies, mostly myeloproliferative neoplasms. In inpatients, surgical complications (71.9%), concurrent/previous splenectomy (50.5%), and infections (44.9%) were the most common causes, whereas hematologic malignancies (56.9%), iron deficiency (36.7%), and previous splenectomy (28.4%) were the most common causes in outpatients. Hematologic malignancy was 3.4 times more likely to be the cause of EXT in outpatients than in inpatients (56.9% vs 16.8%), and a new diagnosis of hematologic malignancy was 1.9 times more likely to be made in outpatients (15.6% vs 8.2%). Eighty-four percent of patients had resolution of EXT within 30 days. One patient died during the period of EXT. Nonsurgical patients with hematologic malignancies had the most prolonged period of EXT. Conclusion Extreme thrombocytosis is a multifactorial hematologic condition, and its etiology differs substantially between inpatients and outpatients. Occult hematologic malignancies are uncommon in EXT when other major causes are present.

Introduction Methemoglobin (MetHb) and sulfhemoglobin (SHb) measurements are useful in the evaluation of cyanosis. When one or both values are elevated, additional analysis is important to establish the etiology of the disorder. Methemoglobinemia occurs from acquired or hereditary causes with diverse treatment considerations, while true sulfhemoglobinemia is only acquired and treatment is restricted to toxin removal. Some toxic exposures can result in a dual increase in MetHb and SHb. Hereditary conditions, such as M-Hemoglobin variants (M-Hbs), can result in increased MetHb and/or SHb values but are clinically compensated and do not require treatment if they are cyanotic but otherwise clinically well. Methods Herein, we report 53 hemoglobin variant cases that have associated MetHb and SHb levels measured by an adapted Evelyn-Malloy laboratory assay method. Results Our data indicate M-Hbs cause variable patterns of MetHb and SHb elevation in a fairly reproducible pattern for the particular variant. In particular, α globin chain M-Hbs can mimic acquired sulfhemoglobinemia due to an isolated increased SHb value. Conclusion If the patient appears clinically well other than cyanosis, M-Hbs should be considered early in the evaluation process to differentiate from acquired conditions to avoid unnecessary testing and treatment regimens and prompt genetic counseling.

The objective of this study is to describe the clinical features and outcomes of patients with the newly defined vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic (VEXAS) syndrome. Nine men with somatic mutations in the UBA1 gene were identified; the most frequent variant was p.Met41Thr (7 of 9, 78%). The median age at VEXAS diagnosis was 74 (67, 76.5) years, and patients had a median duration of symptoms for 4 years before diagnosis. Refractory constitutional symptoms (88%), ear and nose chondritis (55%), and inflammatory arthritis (55%) were common clinical features. Vasculitis was noted in 44%. All patients had significantly elevated inflammatory markers and macrocytic anemia. Thrombocytopenia was present in 66% at diagnosis of VEXAS. Eight patients had bone marrow biopsies performed. All bone marrows were hypercellular, and there was vacuolization of the erythroid (100%) or myeloid precursors (75%). Glucocorticoids attenuated symptoms at prednisone doses ≥20 mg per day, but no other immunosuppressive agent showed consistent long-term control of disease. One patient with coexisting plasma-cell myeloma received plasma-cell-directed therapy with improvement of the inflammatory response, which is a novel finding. In conclusion, VEXAS syndrome is a clinically heterogeneous, treatment-refractory inflammatory condition caused by somatic mutation of the UBA1 gene. Patients often present with overlapping rheumatologic manifestations and persistent hematologic abnormalities. As such, internists and subspecialists, including pathologists, should be aware of this condition to avert diagnostic delay, now that the etiology of this syndrome is known.

Purpose: molecular testing is often indicated for recently transfused patients. However, there are no guidelines regarding the potential interference from donor DNA or whether it is necessary to wait for a period of time post-transfusion prior to genetic testing. While the majority of patients are transfused in the non-trauma setting using leukoreduced (LR) red blood cell products, the degree of leukoreduction varies among centers and is not universally practiced. Methods: whole blood units collected from anonymous donors were used in an in vitro transfusion model. One unit was split: half being leukoreduced simulating a leukopenic recipient and half left untreated. Donors were simulated by leukoreduced, partially leukoreduced (PLR), or non-leukoreduced units, transfused in 2, 5, or 16 unit equivalents. DNA from the combinations were subjected to short tandem repeat (STR) analysis for chimerism detection. Results: donor DNA was not detectable in any of the LR combinations, but detected in the PLR combinations, ranging from 0.1 to 1.5% donor DNA in the immunocompetent recipient and 6.3&ndash, 27.8% in the leukopenic recipient. Non-LR donor DNA was also detected (13&ndash, 95%). Conclusion: donor-derived DNA from leukoreduced blood products is unlikely to interfere with the interpretation of germline genetic testing in immunocompetent recipients but may interfere in immunocompromised recipients.

Hb Bronovo [α103(G10)His→Leu

A novel unstable

Patients with a sole del(20q) chromosomal abnormality and without morphologic features of a myeloid neoplasm (MN) have shown variable clinical outcomes. To explore the potential risk stratification markers in this group of patients, we evaluated their genetic mutational landscape by a 35-gene MN-focused next-generation sequencing (NGS) panel and examined the association of mutations to progression of MNs. Our study included 56 patients over a 10-year period with isolated del(20q), of whom 23 (41.1%) harbored at least one mutation. With a median follow-up of 32.6 months (range: 0.1−159.1), 9 of 23 patients with mutation(s) progressed to MNs, while all 33 patients without mutations did not progress to MN. Kaplan−Meier survival analysis demonstrated the presence of mutation(s) as a significant risk factor for progression to MN (P < 0.0001). MN progression was strongly associated with the presence of non-DNMT3A/TET2/ASXL1 epigenetic modifiers and nonspliceosome mutations (P = 0.003). There was no significant difference among patients with and without MN progression with respect to the number of mutations, variant allele frequency, percentage of del(20q), and other clinical/laboratory variables. This study illustrates the underlying genetic heterogeneity and complexity of isolated del(20q), and underscores the prognostic value of NGS mutational analysis in these cases.

Background Approximately 100 high oxygen affinity (HOA) hemoglobin (Hgb) variants have been reported to date; review of the Mayo Clinic laboratory database (1974-2018) identified 80 distinct variants including 12 novel variants (60 β, 20 α). One-third of HOA Hgb variants result in secondary erythrocytosis, provoking concern regarding increased risk for thrombosis. Current management guidelines lack supporting evidence regarding the utilization of phlebotomy in such cases. We describe presenting features, treatment strategies and follow-up events involving 41 consecutive cases seen at our institution. Methods Study patients were recruited from our institutional laboratory and clinical Hgb variant database. Initial evaluation for Hgb variants was conducted by capillary electrophoresis and high-performance liquid chromatography. Additional testing which included mass spectrometry and isoelectric focusing was pursued as necessary. Since the majority of variants were difficult to identify by protein studies, DNA sequencing of HBB, or HBA1, HBA2 genes was performed for confirmation. Symptoms and thrombosis, both at presentation and during follow up, were recorded. Therapeutic interventions were based on physician discretion and mostly included phlebotomy and/or aspirin therapy; a careful response assessment was performed to determine the impact of each therapy on symptoms and/or thrombosis. Results A total of 41 patients with HOA Hgb variant-associated erythrocytosis (median age 39 years, range 1-81; 54% males) were seen at our institution between January 1973 and February 2020. The majority of the patients carried β-chain variants (n=34; 83%), common variants being Hgb Malmo (n=13), Olympia (n=4), San Diego (n=3), and Wood (n=2). Among the 7 patients with α-chain variants, Hgb Dallas was the most frequent (n=4). Presenting median values (range) for Hgb/Hct, serum erythropoietin and p50 were 18 g/dl/52.9%(16-21.9g/dl/48-66%) 10.4 mIU (4-36.3 mIU), and 20 mmHg (12-25 mmHg), respectively. Family history was documented in 34 patients, of which 24 (71%) reported one or more affected family members. Family history of thrombosis was documented in 7 patients (21%). CV risk factors were present in half of the patients; by contrast, history of thrombosis prior to or at diagnosis was documented in only two patients (5%). Of 23 pregnancies reported in 12 women, live birth rate was 78% (n=18); none of the fetal losses were attributed to erythrocytosis. Active therapies at the time of initial referral consisted of phlebotomy (n=12), aspirin (n=11) and systemic anticoagulation (n=1). At a median follow-up of 10 years (range; 0.04-44), 23 patients had reported one or more symptoms, attributed to hyper-viscosity, such as headaches, fatigue, and lightheadedness. Neither Hct level at diagnosis (p=0.32) nor phlebotomy (p=0.16; 75% patients on vs 52% not on phlebotomy) or aspirin therapy (p=0.75; 55% patients on vs 60% not on aspirin) appeared to influence the occurrence of symptoms. Phlebotomy relieved symptoms in 7 (42%) symptomatic patients; however, 7 (30%) of 23 patients on phlebotomy reported one or more adverse symptoms that were attributed to phlebotomy-induced iron deficiency. Ten patients (24%) experienced thrombosis prior to or following diagnosis: 6 arterial and 4 venous. Median age at thrombotic event was 51 years and median hematocrit 52%; active therapies at the time of event included phlebotomy in 5 patients, aspirin in 4, and systemic anticoagulation in 2. Hct level at diagnosis (p=0.10) or the time of event (p=0.67) did not correlate with occurrence of thrombosis. Additionally, the incidence of thrombosis was no different among patients receiving or not receiving phlebotomy (5/23(22%) vs 5/18(28%), respectively; p=0.66). The presence of CV risk factors was predictive of arterial events (p=0.002). Two of the 4 venous events developed in the context of concomitant thrombophilia. Eight patients (20%), median age 28 years, without CV risk factors, were observed without therapy for a median of 9.5 years (range; 0.4-21) and have not experienced any thrombosis to date. Conclusions We found no association between Hct level and either thrombotic or non-thrombotic symptoms in HOA hemoglobinopathy-associated erythrocytosis; furthermore, implementation of aggressive phlebotomy did not provide a clear benefit with respect to thrombosis risk reduction. Figure 1 Figure 1. Disclosures Patnaik: StemLine: Research Funding; Kura Oncology: Research Funding.

Introduction: VEXAS syndrome (vacuoles, E1 ubiquitin ligase, X-linked, autoinflammatory, somatic) is a newly recognized inflammatory disorder caused by somatic mutations in the UBA1 gene. Bone marrows from these patients reveal a range of morphological changes in hematopoietic precursor cells. In this study, we aim to assess the laboratory indices and morphologic spectrum of bone marrow pathology in VEXAS syndrome. Methods: We identified 16 cases of VEXAS syndrome. All cases had confirmed UBA1 mutation. We reviewed bone marrow biopsies corresponding to the date of diagnosis. This study was approved by the Mayo Clinic Institutional Review Board. Results: All patients were male with a median age of 73 years - associated autoimmune disorders included Sweet syndrome, inflammatory arthritis, relapsing polychondritis and granulomatosis with polyangiitis. 14/16 patients had anemia with median hemoglobin of 10.4 (Range: 6.7- 14.1 g/dL). 15/16 had macrocytosis with median MCV 110.4 (Range: 94.8- 123.1 /fL). 5/16 had thrombocytopenia with median platelet count 174 (Range: 20- 500 x10^9/L). 7/16 had leukopenia with median WBC 3.65 (Range: 2.4- 11.6 x10^9/ L). The ESR and CRP medians were 61.0 mm/hr and 81.5 mg/L, respectively. Karyotype was performed in 12 patients of which 11 were normal and the remaining case showed a complex karyotype. An NGS panel targeting the most frequent myeloid disorder associated gene mutations was negative in 10/15 cases. GS for myeloid mutations revealed pathogenic mutations in 5 patients, involving genes TET2 (2/5), DNMT3A (2/5), and TP53 (1/5). Conclusions: Bone marrow findings in VEXAS syndrome, in this series of 16 patients, are individually non-specific, yet when taken altogether in the overtly abnormal cases, are very suggestive when the clinical index of suspicion is high. In such scenarios, the combined clinical and bone marrow findings should prompt discussion and consideration for UBA1 mutation testing given the significant clinical implications for patient management and prognosis. Disclosures Patnaik: StemLine: Research Funding; Kura Oncology: Research Funding. Warrington: Eli Lilly: Research Funding; Kiniksa: Research Funding.

The εγδβ thalassemias (EGDBT) are infrequently occurring deletions of the β globin gene cluster on chromosome 11. EGDBTs can be an unsuspected cause of severe neonatal anemia that resolves during the first year of life into a normal Hb A2 thalassemic phenotype, presumed to be due to an imbalance of β-like chains during development. First described in 1972, they are categorized into two groups, both with loss of the five DNase I hypersensitivity sites upstream of the β gene (HBB) called the locus control region (LCR). In group 1 deletions, all or most of the β globin gene cluster including HBB is deleted; in group 2 deletions, removal of the LCR silences an intact HBB. Large deletions that do not involve LCR but remove the embryonic (HBE) and fetal genes (HBG2/HBG1) [LCR(ε Gγ Aγ) 0δβ] have not been reported. It is not known whether a deletion with intact LCR as well as δ and β genes would similarly manifest as neonatal anemia that resolves into a normocytic phenotype with normal hemoglobin fraction percentages after infancy. Four individuals with an LCR(ε Gγ Aγ) 0δβ deletion have been evaluated. These include monochorionic, diamniotic twin girls whose newborn screen (NBS) returned significant for Hb A percentage greater than Hb F for both twins. NBS was repeated two weeks later with the same result. The newborns were induced late pre-term (36 weeks and 6 days) after an uncomplicated pregnancy, including no features of twin to twin transfusion. Both infants had no anemia and bilirubin levels remained in the low to low-intermediate risk zones. Neither twin received transfusions or phototherapy during admission. At a follow up visit at 20 months of age a hemoglobin electrophoresis was performed which showed borderline Hb A2 and no Hb F in both twins (Table 1). Ferritin levels were low-normal in Twin A (14 µg/L) and low in Twin B (9 µg/L). Both infants were found to have a heterozygous large deletion affecting HBE, HBG2, HBG1, and HBBP1 loci by Multiplex Ligation-dependent Probe Amplification (MLPA), a method that uses multiple DNA probe pairs to determine the size of the DNA segment deleted. MLPA deletion/duplication testing on the α genes was negative. No β globin variants were identified by DNA sequencing. An evaluation was performed on the 25 year-old healthy mother and showed similar findings including the heterozygous large deletion. Mother and infants continue to be asymptomatic with normal red cell indices for age (Table 1). The fourth was an unrelated 40-year-old female with mild anemia screened by hemoglobin electrophoresis for obstetric evaluation who was found to have borderline Hb A2 (see table 1). MLPA showed a heterozygous deletion involving the same loci. Again, no β globin variants were identified by DNA sequencing. All four cases showed the same MLPA pattern except one non-specific probe commonly altered in common gamma gene conversion events. Long range sequencing performed on one case confirmed a single contiguous 32,599 bp deletion that matched the MLPA data (g.5262276-5294875). The detected deletion has not been reported in literature and differs from EGDBT mutations in that the LCR is intact. As the LCR controls expression of the entire gene cluster, this mutation is expected to display different phenotypic features than classic EGDBT. HBD and HBB are not deleted and therefore adequate transcription of Hb A2 and Hb A are expected with no imbalance of α/β chains after the neonatal period. It is postulated this finding explains the decreased Hb F levels in the NBS test result. The Hb A2 increase is likely a product of this deletion and does not indicate β-thalassemia. The heterozygous absence of HBE and HBG2/HBG1 may result in upregulation of HBD and HBB expression through loss of FKLF and FKLF-2 binding. In addition, HBB-EKLF binding would have less competition as the gamma promoter elements have been heterozygously deleted. In summary, in contrast to classic EGDBTs which cause transient severe neonatal anemia and resolve to normal Hb A2 thalassemic indices, this novel LCR(ε Gγ Aγ) 0δβ deletion was associated with normal CBC values with an absence of severe neonatal anemia, inverted Hb F/Hb A percentages at birth and borderline Hb A2 levels. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Context: Germline predisposition syndromes (GPS) are genetic disorders that increase the risk of all types of malignancies, with a growing list of genes associated specifically with hematological malignancies. Although many of these conditions have syndromic features, some GPS patients present without identifiable traits. We have established a hematology GPS clinic that uses an algorithmic approach to diagnose GPS patients. Objective: To illustrate the heterogeneity of GPS and the benefits of an algorithmic approach to identify non-syndromic GPS patients. Design: Medical records were reviewed retrospectively from patients diagnosed with GPS at our institution from 1994 to 2018. Prospectively, we investigated new pediatric and adult patients with GPS from 2017 to 2020 using an algorithmic approach summarized as follows: 1) Evaluation of relevant family history, 2) phenotype-specific functional assays (telomere measurement, breakage assay, erythrocyte adenosine deaminase testing), 3) germline genetic testing through a custom-designed gene panel, and 4) research whole exome sequencing for negative cases. Both a detailed explanation of the algorithm and the methodology for genetic variant interrogation are included in Mangaonkar et al. MC Proc 2019. Setting: This study was carried out at the Division of Hematology at Mayo Clinic. Patients or Other Participants: GPS was investigated in pediatric and adult patients with one or more first-degree relatives with hematological/visceral malignancies, in those with antecedent thrombocytopenia, or in those with specific features indicative of inherited bone marrow failure (IBMF) (short telomere syndromes, GATA2 haploinsufficiency, Fanconi anemia, Schwachman-Diamond syndrome). Interventions: N/A Main Outcomes Measures: The number of patients diagnosed with GPS both retrospectively and prospectively were tallied and compared. Results: A total of 146 individuals were included in the study divided as follows: 28 (19.4%) presented with hematological malignancy with precedent thrombocytopenia, 27 (18.8%) without precedent thrombocytopenia, 74 (51.3%) showed IBMF, and 15 (10.4%) showed general cancer predisposition syndrome. Eighty-five patients were retrospectively included, while 61 were prospectively evaluated through our algorithmic approach. Among retrospective patients, 7.1% (6 patients) did not present syndromic features, while this value increased to 14.7% (9 patients) when using the algorithmic approach. Conclusions: By using an algorithmic approach, we can identify a higher percentage of GPS patients without syndromic features.

Introduction Germline predisposition syndromes (GPS) are inherited disorders associated with germinal aberrations that increase the risk of malignancies. While aberrations in certain genes increase the risk for all types of malignancies (Tp53, ATM, CDKN2A, CHEK2), there is a growing list of genes associated specifically with hematological malignancies (GATA2, RUNX1, DDX41, ETV6, ANKRD26). At our institution, we have established a hematology GPS clinic to diagnose and manage GPS and with this report, detail our experience with 130 patients. Methods GPS were investigated in pediatric and adult patients with one or more first degree relatives with hematological/visceral malignancies or in those with antecedent thrombocytopenia (ANKRD26, RUNX1, ETV6), or with specific syndromic features (short telomere syndromes/STS, GATA2 haploinsufficiency, Fanconi anemia/FA, Shwachman-Diamond syndrome/SDS). Depending on the phenotype, specific functional assays such as flow-FISH for telomere length assessment and chromosomal breakage assays were ordered. After informed consent and genetic counselling, germline testing was carried out on peripheral blood mononuclear cell, skin fibroblast, or hair follicle-derived DNA. A custom-designed marrow failure NGS panel (200 genes) was used in most cases and interrogation of variants, in silico studies, and functional assays were carried out as previously described (Mangaonkar et al MC Proc 2019). Copy number variations were identified by aCGH. At the time of progression/worsening cytopenias, bone marrow/lymph node biopsies and NGS (next generation sequencing) were carried out where indicated. Results 130 patients with germline predisposition have been identified to date. The spectrum of disorders seen include STS 29 (22%), FA 17 (13%), GATA2 16 (12%), Diamond Blackfan anemia/DBA 13 (10%), RUNX1-FPD 12 (9%), ATM deletions/mutations 11 (8%), ANKRD26 6 (5%), SDS 5 (4%), DDX41 4 (3%), MPL 3 (2%), CHEK2, MECOM, Tp53 mutations 2 (2%) each, and CBL, CEPBA, ELANE, NF1, CDKN2A, CSF3R, ETV6, and GATA1 mutations, 1 (1%) each. Evidence for clonal evolution (CCUS) and hematological malignancies were seen in 51 (39%) patients, involving all the aforementioned genes/syndromes with the exception of DBA, CBL, ETV6, MPL, CSF3R, and GATA1. Seven (64%) of 11 patients with germline ATM deletions/mutations developed lymphoid malignancies; homozygous ATM (Follicular NHL-1, Burkitt lymphoma-1, T-ALL-1, T-LPD-1) and heterozygous ATM (T-PLL-1, DLBCL-1, CLL-1). Clonal evolution occurred in 11 (69%) of 16 GATA2 haploinsufficient patients (CCUS-2, MDS-3, CMML-1, AML-5) and in 7 (58%) of 12 RUNX1-FPD patients (CCUS-1, MDS-1, MDS/MPN-3, AML-2). Five of 29 (17%) STS patients had clonal progression (CCUS-2, MDS-2, AML-1), and 5 (29%) of 17 FA patients progressed to MDS-2 or AML-3. JMML was seen in one patient with a germline NF1 mutation, while 1 (20%) of 5 SDS patients progressed to AML. NGS data at progression was available in 24 (55%) of 44 myeloid/CCUS progressions, with somatic truncating ASXL1 mutations being most frequent (29%), followed by RAS pathway mutations (15%). AML/MDS progressions in STS, FA, and SDS were universally associated with complex/monosomal karyotypes, translating to refractory disease. Seventeen (39%) of 44 patients with myeloid predisposition underwent allogenic HCT (GATA2-7, FA-3, RUNX1-FPD-3, STS-2, NF1-1, Tp53-1), with 10 (59%) being alive at last follow up (Table 1). Conclusion We demonstrate the spectrum of germline aberrations associated with predisposition to hematological malignancies and outline the phenotypic heterogeneity of clonal transformation. The advent of NGS allows identification of clonal progression earlier than morphological changes, with mutations in ASXL1 and RAS pathway genes being commonly implicated. This study supports the universal development of dedicated germline predisposition clinics. Disclosures Pruthi: CSL Behring: Honoraria; Genentech Inc.: Honoraria; Bayer Healthcare: Honoraria; HEMA Biologics: Honoraria; Instrumentation Laboratory: Honoraria; Merck: Honoraria.

Key points Haemoglobin affinity is an integral concept in exercise physiology that impacts oxygen uptake, delivery and consumption. How chronic alterations in haemoglobin affinity impact physiology is unknown. Using human haemoglobin variants, we demonstrate that the affinity of haemoglobin for oxygen is highly correlated with haemoglobin concentration. Using the Fick equation, we model how altered haemoglobin affinity and the associated haemoglobin concentration influences oxygen consumption at rest and during exercise via alterations in cardiac output and mixed-venous P O 2 . The combination of low oxygen affinity haemoglobin and reduced haemoglobin concentration seen in vivo may be unable to support oxygen uptake during moderate or heavy exercise. Abstract The physiological implications, with regard to exercise, of altered haemoglobin affinity for oxygen are not fully understood. Data from the Mayo Clinic Laboratories database of rare human haemoglobin variants reveal a strong inverse correlation (r = -0.82) between blood haemoglobin concentration and P50 , an index of oxygen affinity [Hb = -0.3135(P50 ) + 23.636]. In the present study, observed P50 values for high, normal and low oxygen-affinity haemoglobin variants (13, 26 and 39 mmHg) and corresponding haemoglobin concentrations (19.5, 15.5 and 11.4 g dL-1 respectively) are used to model oxygen consumption as a fraction of delivery at rest ( V O 2 = 0.25 L min-1 , cardiac output = 5.70 L min-1 ) and during exercise ( V O 2 = 2.75 L min-1 , cardiac output = 18.9 l min-1 ). With high-affinity haemoglobin, the model shows that normal levels of oxygen consumption can be achieved at rest and during exercise at the assumed cardiac output levels, with reduced oxygen extraction both at rest (16.8% high affinity vs. 21.7% normal) and during exercise (55.8% high affinity vs. 72.2% normal). With low-affinity haemoglobin, which predicts low haemoglobin concentration, oxygen consumption at rest can be sustained with the assumed cardiac output, with increased oxygen extraction (31.1% low affinity vs. 21.7% normal). However, exercise at 2.75 l min-1 cannot be achieved with the assumed cardiac output, even with 100% oxygen extraction. In conclusion, the model indicates chronic alterations in P50 associate directly with Hb concentration, highlighting that human Hb variants can serve as 'experiments of nature' to address fundamental hypotheses on oxygen transport and exercise.

Multiple algorithms have been published for the evaluation of hereditary erythrocytosis (HE). Typical entry points begin after excluding the more common acquired conditions through investigations of clinical history and assessment of cardiac, pulmonary, or vascular system disorders. Prior exclusion of JAK2 mutations, particularly the common JAK2 V617F mutation, is indicated in adults but less so in pediatric populations. Key decision trees are based on serum erythropoietin levels and p50 results. Recent data reveal some overlap in clinical presentation and laboratory findings in erythrocytosis. Caveats to consider when using algorithmic approaches are discussed.

Nodular fasciitis (NF) is a clonal self-limited neoplastic proliferation characterized by rearrangements of the USP6 locus in most examples. To our knowledge well-documented malignant behavior has never been previously observed in NF. In this report we present an unusual case of NF with classical histologic features that showed a protracted clinical course characterized by multiple recurrences and eventual metastatic behavior over a period of 10 years. Molecular analyses revealed the presence and amplification of the novel PPPR6-USP6 gene fusion, which resulted in USP6 mRNA transcriptional upregulation. These findings further support the oncogenic role of the USP6 protease in mesenchymal neoplasia and expand the biologic potential of NF. © 2016 Wiley Periodicals, Inc.

Background: Molecular genetic testing is increasingly utilized in clinical care, typically with peripheral blood as the preferred specimen. Despite the prevalence of therapeutic blood transfusions, whether donor DNA is present in a sufficient quantity to interfere with recipient genetic testing has not been systematically studied. Microchimerism secondary to transfusion of blood products with donor leukocytes has been well-documented in trauma patients receiving whole blood; however, most medical centers currently transfuse leukoreduced (LR) red blood cell products for non-trauma patients. The degree of leukoreduction varies among centers, but to meet AABB standards must be Methods: We performed an in vitro spiking study utilizing four whole blood units collected from different anonymous donors. Three were leukoreduced at varying levels in order to establish a LR (per our institutional guidelines and standards), a partially leukoreduced (PLR) and a NLR unit, which were then considered "donors". The 4th unit was divided to generate two separate "recipients". The first half was left untreated simulating an immunocompetent recipient while the other was leukoreduced to mimic a leukopenic recipient. Based on a 70 kg patient, we calculated the volume of blood from each "donor" to mix with aliquots of each "recipient" to represent a transfusion of 2, 5, or 16 units, with 2 units corresponding to a double apheresis red blood cell (RBC) transfusion and 16 units corresponding to a near total volume transfusion. DNA was extracted from each individual unit as well as all "transfused" combinations within 24 hours of mixing. Chimerism analysis was then performed by STR analysis using the GlobalFiler PCR amplification kit followed by ChimerMarker analysis software. Results: None of the LR units, despite volume transfused, revealed any level of microchimerism in either the immunocompetent or leukopenic "recipients". The PLR transfused combinations displayed levels ranging from 0.14% to 1.52% of donor chimerism for the immunocompetent "recipient", which is below the limit of detection for most clinical assays evaluating germline genetic variation, and 6.3% to 27.78% of donor chimerism for the leukopenic "recipient", which would be expected to impact a subset of clinical genetic assays. The NLR transfused combinations displayed levels ranging from 13.28% to 95.66% of donor chimerism. Discussion:In vitro "transfusion" of LR RBCs into simulated immunocompetent or leukopenic samples does not lead to detectable donor DNA. However, "transfusion" of PLR and NLR units in an in vitro model reveals significant levels of microchimerism dependent on volume transfused and immune status of the "recipient" which implies possible risk for impact on clinical genetic tests. The minimum time required for clearance of donor leukocytes in the recipient is unknown; we were unable to fully evaluate this and other variables in our in vitro system, but follow-up in vivo studies addressing this question are planned. Disclosures No relevant conflicts of interest to declare.

Background: Genetic variants resulting in quantitative defects in the production of α-spectrin are associated with autosomal recessive hereditary spherocytosis (HS). Because erythroid cells produce α-spectrin in a 3-4:1 ratio in relation to β-spectrin, one defective allele is typically well-tolerated and a single null allele combined with a second partially defective allele may display a sub-clinical phenotype. Protein expression can be reduced by nonsense, frameshift, missense or splicing variants but reported large deletion events are extraordinarily rare (n = 1). Splicing variants include the low expression alleles αLELY - Low Expression LYon (SPTA1:c.6531-12C>T, p.?) and αLEPRA-Low Expression PRAgue (SPTA1:c.4339-99C>T, p.?) which reduce protein expression by 50% and 16%, respectively. Here, we present a family study with a whole gene SPTA1 deletion that characterizes the patient phenotype when a full gene mutation is co-inherited with the αLEPRA and αLELY low expression alleles. Methods: The 6 month-old male proband had a history of congenital Coombs negative hemolytic anemia requiring transfusion from 3 months of age and in whom a red cell membrane disorder was clinically suspected. Pretransfusion CBC and peripheral blood smear results were unknown. Transfused CBC indices were as follows: RBC 4 x 1012/L, HGB 11 g/dL, MCV 76 fL, MCH 27 pg, MCHC 36 g/dL and a reticulocyte count of 1.8%. The proband's mother, of Cuban descent, and father, of European descent, had no history of anemia or HS. Targeted high throughput sequencing of genes related to hereditary hemolytic anemia was performed for the detection of single nucleotide variants (SNVs) and small insertion/deletion variants (indels). Relative quantitative real time PCR (RT-PCR) was utilized to confirm large structural variants. Results: Sequencing identified a large heterozygous deletion that spanned the entire SPTA1 gene (NC_000001.11:g.(?_158656337)_(158581024_?) in the proband and his mother. In addition, the proband had inherited hemizygous αLEPRA from his father. The mother had hemizgous αLELY. The father showed heterozygous αLEPRA and no other SPTA1 variants (Table 1). Conclusion: To our knowledge, only Iolascon et al in 2011 has reported a SPTA1 gene large deletion (SpectrinExeter, exon 11-exon 12 deletion, loss of 83 amino acids) which resulted in a structurally abnormal protein and ellipto-poikilocytosis phenotype when in trans to αLELY. Our current case is the first reported SPTA1 full gene deletion and our family study allows comparison of the effects of coinheritance of the low expression alleles αLEPRA and αLELY. When in combination with complete absence of the SPTA1 gene in trans configuration, αLELY manifests in subclinical effects and αLEPRA causes a recessive HS phenotype, which resulted in severe anemia. This contrast further demonstrates that, unlike αLEPRA, αLELY does not decrease the α-spectrin concentration sufficiently to contribute to the baseline phenotype regardless of the severity of the second allele mutation for quantitative disorders such as HS. Disclosures No relevant conflicts of interest to declare.

Background: Voxelotor (GBT440) is a small molecule allosteric effector with high specificity for hemoglobin (Hb) that inhibits Hb S polymerization by increasing hemoglobin oxygen affinity. Developed as an oral, once-daily medication, it is undergoing phase 3 randomized clinical trials in sickle cell disease patients. Therapeutic monitoring of Hb quantitative fractions is routine in sickle cell disease patients to assess medication and transfusion effects and future treatment requirements. In the clinical laboratory, some therapies can alter the Hb fraction percentages or characteristic protein migration/elution patterns and can mimic complex hemoglobinopathy disorders causing misinterpretation or unnecessary additional testing. We present the effects of voxelotor on hemoglobin identification/monitoring testing in multiple testing platforms. Methods: A whole blood anticoagulated sample from a male patient who was undergoing treatment for sickle cell disease was received for routine hemoglobin testing. Five additional samples with similar features were also received from three male patients (age range of all patients was 18 to 22 years) with sickle cell disease. Hemoglobin protein analysis was performed using standard methods including cation-exchange high performance liquid chromatography (HPLC), capillary electrophoresis (CE), isoelectric focusing (IEF), intact globin chain mass spectrometry (MS), sickle solubility and hemoglobin stability studies. DNA sequencing of the alpha (HBA1/HBA2) and beta globin (HBB) genes was performed on one sample. Results: CE (initial and 50:50 mix, figures 1A and 1B, respectively) revealed a Hb S peak with a shoulder and additional small peaks at position 203 (D zone) and 234 (cusp of zones E/A2). In some cases the 234 peak interfered with instrument designation of the A2 peak (50:50 mix with normal) and shifted the Hb S peak into the E zone which risks variant misidentification (figure 1C). Our laboratory overcame this limitation by substituting the normal sample with beta thalassemia trait to enhance the Hb A2 peak after mixing. HPLC tracings (figure 1D) showed a duplex peak pattern in the D and S windows with separate peak quantification percentages (index case showed elution at 4.18 and 4.37 minutes with 14.9% and 66.4%, respectively). The dual peaks detected by HPLC partially mimicked compound Hb S/D-Punjab. IEF (figure 1E) showed additional bands at -4.7, and -11.5 (Schneider-Barwick ratios). The additional peaks identified by CE and IEF mimicked an alpha chain hemoglobin variant; however, the expected hybrid patterns were atypical prompting further investigation. Sickle solubility was positive, heat stability studies were negative and mass spectrometry did not definitively detect abnormal peaks other than βS. DNA sequencing of the alpha and beta globin genes did not reveal abnormalities other than homozygous Hb S. Similar hemoglobin patterns were identified in all samples tested. Conclusion: Voxelotor treatment in sickle cell patients results in a distinctive pattern alteration in hemoglobin testing. Methods may not give accurate variant percentage estimation and the treatment may result in shifts in variant mobility causing erroneous laboratory results. Novel therapies are increasing in the treatment of hemoglobin disorders and medication effect should be a consideration when atypical patterns are encountered in the laboratory. Knowledge of these artifacts by clinicians and laboratorians is paramount to avoid erroneous diagnosis, unnecessary additional testing and inaccurate Hb variant quantitation for monitoring purposes. Notification of current treatment regimens to testing facilities is highly recommended in these patients. Figure 1 Disclosures No relevant conflicts of interest to declare.

Introduction: Globin gene sequencing has long been impeded by repetitive regions, homology and structural variation. Currently, long-read sequencing technology has been limited by high cost and error rate. These challenges can be mitigated by sample multiplexing of targeted capture sequencing and the use of consensus reads, respectively. This ongoing study analyzes the utility of long range sequencing technology in identifying historically problematic beta globin cluster mutations. Materials and methods: Long range sequencing was performed on complex beta globin gene cluster cases utilizing the Sequel platform (Pacific Biosciences, Menlo Park, California, United States). Sample input was 1 microgram of DNA extracted from whole blood. Circular Consensus Sequence (CCS) FASTQ sequences files were mapped to reference genome (GRCh37/hg19) using NGMLR, followed by annotation of variants using a custom bioinformatics workflow. Comparison to multiplex ligation-dependent probe amplification (MLPA), Sanger sequencing, array CGH, short-range NGS (300 bp), hemoglobin protein, and clinical data was performed. Results: CCS read length varied from 1 to 10 kb, average 3.5. Analysis of the beta globin cluster region showed impressive superiority and comprehensiveness to Sanger, MLPA, array CGH and short range sequencing technology: 1) single nucleotide variants (SNVs) were identified to a sensitivity and specificity of 99.5%; 2) large structural variants (SVs) such as large deletions, duplications, insertions, crossovers and fusions spanning many kilobases were characterized in the heterozygous, homozygous and compound heterozygous state to a precise genomic coordinate (table 1); 3) phasing SNVs identified Hb S haplotypes (Central African region (CAR), Benin, Senegal, Arab-Indian and Cameroon). Conclusion: 1) Long range sequencing holds significant promise in genotyping hemoglobin disorders. This method improves efficiency with potential for a single test offering with increased resolution, particularly in large deletion analysis. Complex cases greatly benefited from improved range and resolution. 2) The decreased requirement of blood volume for extensive testing is of particular interest for the pediatric population. 3) Genotyping of Hb S patients detected by positive newborn screening will help predict need for prophylaxis or therapy by assessing variant zygosity, phasing and haplotypes. In conclusion, we believe that long range sequencing has immense potential to contribute extensively to thalassemia and hemoglobinopathy diagnostics and is far superior to the currently available technologies for beta globin cluster analysis. Disclosures Jen: Celgene: Employment.

Hereditary erythrocytosis is associated with high oxygen affinity hemoglobin variants (HOAs), 2,3-bisphosphoglycerate deficiency and abnormalities in EPOR and the oxygen-sensing pathway proteins PHD, HIF2α, and VHL. Our laboratory has 40 years of experience with hemoglobin disorder testing and we have characterized HOAs using varied protein and molecular techniques including functional assessment by p50 analysis. In addition, we have more recently commenced adding the assessment of clinically relevant regions of the VHL, BPGM, EPOR, EGLN1 (PHD2), and EPAS1 (HIF2A) genes in a more comprehensive hereditary erythrocytosis panel of tests. Review of our experience confirms a wide spectrum of alterations associated with erythrocytosis which we have correlated with phenotypic and clinical features. Through generic hemoglobinopathy testing we have identified 762 patients with 81 distinct HOA Hb variants (61 β, 20 α), including 12 that were first identified by our laboratory. Of the 1192 cases received for an evaluation specific for hereditary erythrocytosis, approximately 12% had reportable alterations: 85 pathogenic/likely pathogenic mutations and 58 variants of unknown significance. Many have not been previously reported. Correlation with clinical and phenotypic data supports an algorithmic approach to guide economical evaluation; although, testing is expanded if the suspected causes are negative or of uncertain significance. Clinical features are similar and range from asymptomatic to recurrent headaches, fatigue, restless legs, chest pain, exertional dyspnea and thrombotic episodes. Many patients were chronically phlebotomized with reported relief of symptoms. This article is protected by copyright. All rights reserved.