Search

The neonatal hemostatic system is different from that of adults. The differences in levels of procoagulant and anticoagulant factors and the evolving equilibrium in secondary hemostasis during the transition from fetal/neonatal life to infancy, childhood, and adult life are known as "developmental hemostasis." In regard to primary hemostasis, while the number (150,000–450,000/µl) and structure of platelets in healthy neonates closely resemble those of adults, there are significant functional differences between neonatal and adult platelets. Specifically, platelets derived from both cord blood and neonatal peripheral blood are less reactive than adult platelets to agonists, such as adenosine diphosphate (ADP), epinephrine, collagen, thrombin, and thromboxane (TXA2) analogs. This platelet hyporeactivity is due to differences in expression levels of key surface receptors and/or in signaling pathways, and is more pronounced in preterm neonates. Despite these differences in platelet function, bleeding times and PFA-100 closure times (an in vitro test of whole-blood primary hemostasis) are shorter in healthy full-term infants than in adults, reflecting enhanced primary hemostasis. This paradoxical finding is explained by the presence of factors in neonatal blood that increase the platelet-vessel wall interaction, such as high von Willebrand factor (vWF) levels, predominance of ultralong vWF multimers, high hematocrit, and high red cell mean corpuscular volume. Thus, the hyporeactivity of neonatal platelets should not be viewed as a developmental deficiency, but rather as an integral part of a developmentally unique, but well balanced, primary hemostatic system. In clinical practice, due to the high incidence of bleeding (especially intraventricular hemorrhage, IVH) among preterm infants, neonatologists frequently transfuse platelets to non-bleeding neonates when platelet counts fall below an arbitrary limit, typically higher than that used in older children and adults. However, recent studies have shown that prophylactic platelet transfusions not only fail to decrease bleeding in preterm neonates, but are associated with increased neonatal morbidity and mortality. In this review, we will describe the developmental differences in platelet function and primary hemostasis between neonates and adults, and will analyze the implications of these differences to platelet transfusion decisions. [ABSTRACT FROM AUTHOR]

The present study assessed the criteria for initiating cytoreduction and response to conventional therapies in 1446 patients with essential thrombocythemia (ET), 267 (17%) of which were CALR‐mutated. In low risk patients, time from diagnosis to cytoreduction was shorter in CALR‐positive than in the other genotypes (2·8, 3·2, 7·4 and 12·5 years for CALR, MPL, JAK2V617F and TN, respectively, P < 0·0001). A total of 1104 (76%) patients received cytoreductive treatment with hydroxycarbamide (HC) (n = 977), anagrelide (n = 113), or others (n = 14). The estimated cumulative rates of complete haematological response (CR) at 12 months were 40 % and 67% in CALR and JAK2V617F genotypes, respectively. Median time to CR was 192 days for JAK2V617F, 343 for TN, 433 for MPL, and 705 for CALR genotypes (P < 0·0001). Duration of CR was shorter in CALR‐mutated ET than in the remaining patients (P = 0·003). In CALR‐positive patients, HC and anagrelide had similar efficacy in terms of response rates and duration. CALR‐mutated patients developed resistance/intolerance to HC more frequently (5%, 23%, 27% and 15% for JAK2V617F, CALR, MPL and TN, respectively; P < 0·0001). In conclusion, conventional cytoreductive agents are less effective in CALR‐mutated ET, highlighting the need for new treatment modalities and redefinition of haematologic targets for patients with this genotype. [ABSTRACT FROM AUTHOR]

Objectives: In patients with essential thrombocythemia (ET), after the JAK2V617F driver mutation, mutations in CALR are common (classified as type 1, 52‐bp deletion or type 2, 5‐bp insertion). CALR mutations have generally been associated with a lower risk of thrombosis. This study aimed to confirm the impact of CALR mutation type on thrombotic risk. Methods: We retrospectively investigated 983 ET patients diagnosed in Spanish and Polish hospitals. Results: With 7.5 years of median follow‐up from diagnosis, 155 patients (15.8%) had one or more thrombotic event. The 5‐year thrombosis‐free survival (TFS) rate was 83.8%, 91.6% and 93.9% for the JAK2V617F, CALR‐type 1 and CALR‐type 2 groups, respectively (P =.002). Comparing CALR‐type 1 and CALR‐type 2 groups, TFS for venous thrombosis was lower in CALR‐type 1 (P =.046), with no difference in TFS for arterial thrombosis observed. The cumulative incidence of thrombosis was significantly different comparing JAK2V617F vs CALR‐type 2 groups but not JAK2V617F vs CALR‐type 1 groups. Moreover, CALR‐type 2 mutation was a statistically significant protective factor for thrombosis with respect to JAK2V617F in multivariate logistic regression (OR: 0.45, P =.04) adjusted by age. Conclusions: Our results suggest that CALR mutation type has prognostic value for the stratification of thrombotic risk in ET patients. [ABSTRACT FROM AUTHOR]

Patients with polycythemia vera (PV) or essential thrombocythemia (ET) presenting with splanchnic vein thrombosis (SVT) might have a specific clinico-biological profile. To investigate this hypothesis, 3705 PV/ET patients from three national registers, 118 of them presenting with SVT, were reviewed. After correction for age and sex, PV/ET patients with SVT showed an increased risk of death (HR 2.47, 95% CI 1.5-4.01, p < 0.001), venous thrombosis (IRR 3.4, 95%CI 2.1-5.5, p < 0.001), major bleeding (IRR 3.6, 95%CI 2.3-5.5, p < 0.001), and second cancer (IRR 2.37, 95%CI 1.4-4.1, p = 0.002). No case of acute leukemia was documented among patients with PV/ET presenting with SVT and seven of them (6%) progressed to myelofibrosis. SVT was not associated with lower risk of MF after correction by age and sex. Patients with SVT more frequently died from complications related to hepatic disease, major bleeding, or second cancer, resulting in a 5-year reduction of age- and sex-adjusted median survival. In conclusion, PV and ET patients presenting with SVT have shorter survival than patients with PV and ET of the same age and sex. This excess mortality is related to liver disease, major bleeding, and second cancer rather than to the natural evolution of the MPN. [ABSTRACT FROM AUTHOR]

Background: The mechanisms underlying neonatal platelets hyporesponsiveness are not fully understood. While previous studies have demonstrated developmental impairment of agonist-induced platelet activation, differences in inhibitory signaling pathways have been scarcely investigated. Objective: To compare neonatal and adult platelets with regard to inhibition of platelet reactivity by prostaglandin E1 (PGE1). Methods: Platelet-rich plasma from umbilical cord (CB) or adult blood was incubated with PGE1 (0–1 μM). We assessed aggregation in response to adenosine diphosphate (ADP), collagen, and thrombin receptor activating peptide as well as cyclic adenosine 3′5′-monophosphate (cAMP) levels (ELISA). Gαs, Gαi2, and total- and phospho-protein kinase A (PKA) were evaluated in adult and CB ultrapure and washed platelets, respectively, by immunoblotting. Results: Neonatal (vs. adult) platelets display hypersensitivity to inhibition by PGE1 of platelet aggregation induced by ADP and collagen (PGE1 IC50: 14 and 117 nM for ADP and collagen, respectively, vs. 149 and 491 nM in adults). They also show increased basal and PGE1-induced cAMP levels. Mechanistically, PGE1 acts by binding to the prostanoid receptor IP (prostacyclin receptor), which couples to the Gαs protein-adenylate cyclase axis and increases intracellular levels of cAMP. cAMP activates PKA, which phosphorylates different target inhibitor proteins. Neonatal platelets showed higher basal and PGE1-induced cAMP levels, higher Gαs protein expression, and a trend to increased PKA-dependent protein phosphorylation compared to adult platelets. Conclusion: Neonatal platelets have a functionally increased PGE1-cAMP-PKA axis. This finding supports a downregulation of inhibitory when going from neonate to adult contributing to neonatal platelet hyporesponsiveness. [ABSTRACT FROM AUTHOR]

The RASGRP2 gene encodes the Ca2+ and DAG-regulated guanine nucleotide exchange factor I (CalDAG-GEFI), which plays a key role in integrin activation in platelets and neutrophils. We here report two new RASGRP2 variants associated with platelet dysfunction and bleeding in patients. The homozygous patients had normal platelet and neutrophil counts and morphology. Platelet phenotyping showed: prolonged PFA-100 closure times; normal expression of major glycoprotein receptors; severely reduced platelet aggregation response to ADP and collagen (both patients); aggregation response to PAR1 and arachidonic acid markedly impaired in one patient; PMA-induced aggregation unaffected; platelet secretion, clot retraction, and spreading minimally affected. Genetic analysis identified two new homozygous variants in RASGRP2: c.706C>T (p.Q236X) and c.887G>A (p.C296Y). In both patients, CalDAGGEFI protein was not detectable in platelet lysates, and platelet αIIbβ3 activation, as assessed by fibrinogen binding, was greatly impaired in response to all agonists except PMA. Patient neutrophils showed normal integrin expression, but impaired Mn2+-induced fibrinogen binding. In summary, we have identified two new RASGRP2 mutations that can be added to this rapidly growing form of inherited platelet function disorder. [ABSTRACT FROM AUTHOR]

Our objective is to describe a chronic myeloid leukemia patient with a severe liver toxicity likely due to a drug–drug interaction between imatinib and sertraline. The patient started treatment with sertraline three months after starting imatinib. From the beginning of sertraline treatment, the patient developed vomiting, and five weeks later she developed a severe hepatic failure and was admitted to the hospital. The Naranjo nomogram showed a probable correlation between this adverse effect and the interaction between imatinib and sertraline. This interaction is extremely rare and the mechanism of action is not clear; it could be a mix of pharmacokinetic and pharmacodynamic processes. To our knowledge, this is the first case in medical literature of a severe liver toxicity due to an interaction between imatinib and sertraline. This interaction is also not described in the main secondary data sources, such as Lexicomp® and Micromedex®. However, due to the severity of this event, the hepatic function should be carefully monitored in patients treated with imatinib and sertraline. [ABSTRACT FROM AUTHOR]

This study has retrospectively analyzed the efficacy of single-agent prednisone, usually given after failure of other therapies, in 30 patients with myelofibrosis (MF) and severe anemia. Initial dose was 0.5-1 mg/kg daily, with tapering to the minimum effective dose in responders. Twelve patients (40%) achieved anemia response according to the revised International Working Group for Myelofibrosis Research and Treatment criteria, after a median time of 1.1 months on treatment. Median response duration was 12.3 months. Patients with constitutional symptoms or > 2% circulating blasts had a trend for a lower response rate. A platelet increase > 50 x 109/L was observed in three out of 11 patients with baseline counts < 100 x 109/L. Median survival from prednisone start was significantly longer in anemia responders (5.0 years, 95% CI = 3.5-6.5, vs 1.5 years, 95% CI = 0.2-2.8; p = 0.002). Prednisone can improve the anemia and thrombocytopenia in selected MF patients after failure to standard therapies. [ABSTRACT FROM AUTHOR]