New Horizons in Fetal and Neonatal Alloimmune Thrombocytopenia.

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a common cause of severe thrombocytopenia in newborns. Intracranial bleeding may lead to severe neurological sequelae and mortality. Current management of pregnancies at risk is suboptimal. Prenatal FNAIT diagnosis commonly requires invasive procedures and therapy is associated with a high treatment burden. The present review explores advances in the field and their potential contribution to modification of the diagnostic and therapeutic landscape. Topics addressed include the role of noninvasive prenatal testing using fetal cell free DNA, insights into novel and prospective therapeutic options achieved through the development of murine models of FNAIT as well as the forecast for the progress in pregnancy risk stratification through advancement in the investigation of biological characteristics of alloantibodies and their association with the risk of fetal bleeding.

Neonatal Thrombocytopenia: Differing Characteristics of NAIT Versus Non-NAIT.

While neonatal alloimmune thrombocytopenia (NAIT) is the most common cause of severe neonatal thrombocytopenia good clinical predictors are lacking. We analyzed cases of neonatal thrombocytopenia in Schneider Children's Medical Center of Israel to pinpoint qualifiers of NAIT (NAIT+) in comparison to non-NAIT (NAIT-) thrombocytopenia. Patient and maternal data were retrospectively collected on all thrombocytopenic newborns undergoing a workup for NAIT in our tertiary center between 2001 and 2016. Among 26 thrombocytopenic neonates, the mean nadir in NAIT+ patients (25×10 9 /L) was significantly lower than NAIT- patients (64×10 9 /L) ( P <0.001). 61.5% of NAIT+ infants required treatment compared with 23% of non-NAIT ( P =0.015). NAIT+ patients also required more therapeutic modalities than infants with NAIT- thrombocytopenia. Human platelet antigen (HPA)-1a and HPA-5b alloantibodies most frequently caused NAIT. In summary, thrombocytopenia in NAIT+ was significantly more severe compared with NAIT- and more likely to require treatment. In addition, despite the varied ethnic population in Israel, the HPA alloantibodies found in our population were most similar to those common in Western countries. In the absence of rigorous prenatal screening options, we suggest platelet counts below 40 to 50×10 9 /L in a healthy newborn be considered most suggestive for NAIT and warrant urgent NAIT-specific analysis.

Effect of Prolonged Hypothermic Cardiopulmonary Bypass, Heparin, and Protamine on Platelet: A Small-Group Study.

Cardiopulmonary bypass (CPB) is associated with platelet dysfunction (PD), an important cause of postoperative bleeding. The etiology of PD is not completely understood. We mapped the platelets' function during CPB to determine the etiology of PD. Platelets activation, measured by procaspase activating compound-1 and P-selectin expression (CD62P), after activation by adenosine diphosphate and thrombin receptor activator peptide, were decreased by protamine. Changes during CPB were insignificant. Platelet-leukocyte aggregation was increased by CPB but not by protamine. Platelet apoptosis marker, annexin V, was increased by protamine. Changes during CPB were insignificant. Our findings demonstrate that protamine given after CPB plays a central role in PD and count decrease.

[FETAL/NEONATAL ALLOIMMUNE THROMBOCYTOPENIA (F/NAIT) - THE PREVALENCE VERSUS AWARENESS OF A LIFE-THREATENING CLINICAL CONDITION].

AIMS: To determine the prevalence and incidence of HPA antigens and antibodies in the Israeli population and to evaluate the degree of awareness to F/NAIT in Israel. BACKGROUND: In fetal/neonatal alloimmune thrombocytopenia (F/NAIT) the fetus suffers from thrombocytopenia mediated by maternal IgG antibodies directed against fetal platelets leading to intracranial hemorrhage (ICH) in about 20% of cases. The antibodies are directed against Human Platelet Antigens (HPA). Diagnosis of F/NAIT is essential because thrombocytopenia may recur and worsen in subsequent pregnancies; hence awareness of F/NAIT is crucial. METHODS: We conducted a retrospective analysis of cases referred to the platelet immunology laboratory between the years 2011-2015 and medical records of newborns born at Rambam Medical Center during 2010-2015. RESULTS: Of the 322 cases studied, 175 (54.35%) had anti-platelet antibodies. The most common antibody was anti-HPA1a (41.85%) followed by anti-HPA5b (28.75%). The prevalence of HPA antigens was similar to that of the Caucasian population. About 80% of the cases were referred due to neonatal thrombocytopenia, found in a random blood count or after bleeding, and 13% of cases were referred due to suspected ICH during pregnancy. In only 22.6% of cases, the diagnosis was made immediately after birth, and 18.7% of the suspected cases were referred only during the subsequent pregnancy. About 84% of infants with severe thrombocytopenia were not referred to F/NAIT diagnosis. CONCLUSIONS: The prevalence of platelet antigens in the Israeli population is similar to that of the Caucasian population. The paucity of referrals points to the need to establish diagnostic guidelines and raise awareness among caregivers.

Intravenous immunoglobulin-induced acute thrombocytopenia.

BACKGROUND: Intravenous immunoglobulin (IVIG) has known efficacy in various hematologic conditions, including immune thrombocytopenic purpura. STUDY DESIGN AND METHODS: We present the clinical course of a patient with splenic marginal zone lymphoma, who developed acute thrombocytopenia on three consecutive episodes, with nadir counts of 27 × 109 , 50 × 109 , and 9 × 109 /L, upon administration of Intratect IVIG for hypogammaglobulinemia. An immunofluorescence test applying flow cytometry and monoclonal antibody immobilization of platelet antigens (MAIPA) assay were used to evaluate the reaction between IgG present in the IVIG preparations and the patient's or healthy donors' platelets (PLTs). RESULTS: A strong direct binding reaction was observed between the patient's PLTs and Intratect IgG using both methods. A similar reaction failed to materialize with controls. Binding was not antigen specific according to MAIPA. CONCLUSIONS: This is the first reported case of thrombocytopenia as a possible adverse effect of IVIG.

Severe complicated neutropenia in two patients with metastatic non-small-cell lung cancer treated with nivolumab.

Checkpoint inhibitors effectively enhance the natural immune response against cancer, but they are also known to induce a unique spectrum of immune-related adverse events. Here, we report the first case of isolated neutropenia subsequent to nivolumab therapy. Prominent activated T-cells were found in the patient's serum and bone marrow alongside evidence of maturational defects in neutrophil precursors. Antineutrophil antibodies were not detected despite reliable testing techniques. A T-cell-mediated response is probable, consistent with the established mechanism for the development of other immune-related toxicities. Awareness of this rare and severe side effect reinforces the importance of early diagnosis and prompt initiation of proper treatment.

Immune-mediated mechanism for thrombocytopenia after Loxosceles spider bite.

Loxoscelism, characterized by high fever, vomiting, malaise, a dermonecrotic lesion, and thrombocytopenia, was diagnosed in a 3-year-old female. Clinical laboratory and dermatological signs are described. Blood test showed a transient hypercoagulable state and the presence of IgG antibodies against platelets, suggesting an immune-mediated mechanism for platelet destruction, in addition to the direct toxic effect of the spider venom. The finding of platelet antibodies after a Loxosceles spider bite has not been previously reported.

Alloimmune platelet transfusion refractoriness circumvented by allogeneic stem cell transplantation.

BACKGROUND: Administration of intensive chemotherapy used in the management of malignancies is accompanied with marrow suppression. Patients undergoing such treatments and especially those with acute leukemia need prolonged blood component support and are at risk for platelet (PLT) refractoriness. Irradiated and filtered blood, although effective, does not eliminate the risk for refractoriness and consequent fatal hemorrhage. STUDY DESIGN AND METHODS: The current report presents a case of an acute myeloid leukemia patient who became alloimmunized to multiple HLA antigens after complicated autologous stem cell transplantation and to whom granulocytes were transfused as part of treatment for overwhelming sepsis. Poor engraftment necessitated prolonged transfusion dependency with rare HLA-compatible donors detected according to the indirect PLT immunofluorescence test. During the proceeding weeks the patient suffered from recurrent severe attacks of gastrointestinal bleeding. When several conservative treatments failed, a fully HLA-matched, bidirectionally ABO-incompatible allogeneic transplantation from a sibling donor was performed. RESULTS: Allogeneic transplantation was uneventful, with stable full donor-derived lymphohematopoietic engraftment. CONCLUSION: Immune PLT refractoriness can appear at later stages of treatment even in severely immunocompromised patients. Granulocyte transfusions could lead to alloimmunization and should therefore be cautiously considered in this patient population.

Early-onset plasmapheresis and LDL-apheresis provide better disease control for pediatric homozygous familial hypercholesterolemia than HMG-CoA reductase inhibitors and ameliorate atherosclerosis.

Plasmapheresis (PA) and low-density lipoprotein apheresis (LDL-A) were assessed in five children with homozygous familial hypercholesterolemia (HFH) previously receiving statins. LDL-A required smaller extracorporeal blood volumes. Mean HDL-cholesterol reduction post-procedure was 32% and 60% with LDL-A and PA, respectively. Non-HDL-C reduction was 64% and 69%, respectively. Pre-procedural LDL-C decreased significantly with weekly versus biweekly LDL-A. Carotid intimal media thickness (IMT) studies demonstrated disappearance of atheromatous lesions and normal ITM in 4/5 patients. Echocardiography revealed normal aortic valves, coronary orifices and supra-valvular area in all patients. Apheresis is effective in pediatric HFH. It may be started in patients weighing 14 kg.

Rituximab-associated acute thrombocytopenia: an under-diagnosed phenomenon.

Acute infusion reactions are the most common documented adverse reactions reported with rituximab, with overt cytokine release syndrome, and hematological adverse events being much rarer. The clinical course of a patient with mantle cell lymphoma, who developed acute thrombocytopenia and leukopenia following rituximab administration, is described and the literature reviewed. Serum complement and the levels of three cytokines--TNF-alpha, IL-6, and IL-1, were measured 2 days after the infusion of rituximab by using ELISA assay. Drug-dependent antibodies against platelets were evaluated by two procedures as follows: an immunofluorescence test applying flow cytometry and Monoclonal Antibody Immobilization of Platelet Antigen (MAIPA). Serum levels of TNF-a were significantly increased compared with normal, whereas those of IL-6 and IL-1 were not increased significantly. Flow cytometry assay and the MAIPA assay failed to detect rituximab-dependent antibodies against platelets. Complement levels were decreased compared with normal. Literature search yielded 10 publications reporting on another 15 patients. The most common type of lymphoma was mantle cell lymphoma, six patients had bone marrow involvement, and 10 patients had splenomegaly. In 10 patients, acute cytopenia was preceded by cytokine release syndrome or infusion-related symptoms. Usually, thrombocytopenia was not associated with bleeding manifestations. Thrombocytopenia was the most commonly acute cytopenia reported. The postulated pathogenesis is associated with cytokine release syndrome and complement activation. Patients with potential risk factors like splenomegaly and bone marrow involvement, who develop clinical manifestations compatible with cytokine release syndrome, should be closely monitored for rituximab-associated cytopenia.

Impact of red blood cell transfusion on clinical outcomes in patients with acute myocardial infarction.

Divergent views remain regarding the safety of treating anemia with red blood cell (RBC) transfusion in patients with acute coronary syndrome (ACS). We used a prospective database to study effect of RBC transfusion in patients with acute myocardial infarction (MI; n = 2,358). Cox regression models were used to determine the association between RBC transfusion and 6-month outcomes, incorporating transfusion as a time-dependent variable. The models adjusted for baseline variables, propensity for transfusion, and nadir hemoglobin previous to the transfusion. One hundred ninety-two patients (8.1%) received RBC transfusion. Six-month mortality rates were higher in patients receiving transfusion (28.1% vs 11.7%, p <0.0001). The adjusted hazard ratio (HR) for mortality was 1.9 in transfused patients (95% confidence interval [CI] 1.3 to 2.9). Interaction between RBC transfusion and nadir hemoglobin with respect to mortality (p = 0.004) was significant. Stratified analyses showed a protective effect of transfusion in patients with nadir hemoglobin < or=8 g/dL (adjusted HR 0.13, 95% CI 0.03 to 0.65, p = 0.013). By contrast, transfusion was associated with increased mortality in patients with nadir hemoglobin >8 g/dL (adjusted HR 2.2, 95% CI 1.5 to 3.3; p <0.0001). Similar results were obtained for the composite end point of death/MI/heart failure (p for interaction = 0.04). In conclusion, RBC transfusion in patients with acute MI and hemoglobin < or =8 g/dL may be appropriate. The increased mortality observed in transfused patients with nadir hemoglobin above 8 g/dL underscores the clinical difficulty of balancing risks and benefits of RBC transfusion in the setting of ACS.

Transfusion medicine during the summer of 2006: lessons learned in northern Israel.

In July 2006 a Hizballah attack erupted at the Lebanon-Israel border. Reported here is the experience of the Rambam Health Care Campus--a level I trauma center--during 33 days of warfare. Two hundred ninety-five soldiers and 209 civilians were admitted to the emergency department (ED). Forty-eight wounded soldiers (16%) and 12 civilians (6%) had transfusion. Twenty soldiers and 1 civilian had massive transfusions. The ratio between packed red blood cells and fresh frozen plasma (FFP) used for patients who had massive transfusion was 3:2. In these patients, the median prothrombin time international normalized ratio and partial thromboplastin time increased during the first 2 hours after admission from 1.29 to 1.51 and from 33.6 to 39 seconds, respectively. Twenty patients who had massive transfusion survived. Patients with an injury severity score of at least 16 had a higher need for blood products than others, with a lower severity score, with a mean packed red blood cells unit transfusion of 7 vs 4 (P = .03) and FFP transfusion of 13 vs 1.5 (P = .002), respectively. In conclusion, we observed that early transfusion of FFP to casualties with penetrating wounds requiring massive transfusion is needed to overcome the coagulopathy present. The presence of a transfusion service representative on-site in the ED is recommended to ensure proper identification and labeling of blood samples. Real-time consultations provided by a transfusion medicine physician in the operation theater was also found to be essential.

Taking a wider view on fetal/neonatal alloimmune thrombocytopenia.

In fetal/neonatal alloimmune thrombocytopenia (FNAIT), platelets are destroyed by maternal antibodies directed against fetal/neonate antigens. Thrombocytopenia can be severe and lead to intracranial hemorrhage (ICH) in about 10% of cases. Although three types of antigen groups, presented on platelets [ABO blood group antigens, human leukocyte antigens (HLA) and human platelet antigens (HPA)] are known to be implicated in immune platelet destruction, antibodies against HPA are most commonly involved in FNAIT and hence are the target of extensive research. Awareness of FNAIT by physicians as well as the availability of the most sensitive diagnostic methods capable of detecting a wide range of antibodies are crucial for the diagnosis of FNAIT and the prevention of severe thrombocytopenia and its bleeding risks in subsequent pregnancies.

Thrombin is a selective inducer of heparanase release from platelets and granulocytes via protease-activated receptor-1.

Heparanase, known to be involved in angiogenesis and metastasis, was shown to form a complex with tissue factor (TF) and to enhance the generation of factor Xa. Platelets and granulocytes contain abundant amounts of heparanase that may enhance the coagulation system upon discharge. It was the aim of this study to identify the inducer and pathway of heparanase release from these cells. Platelets and granulocytes were purified from pooled normal plasma and were incubated with ATP, ADP, epinephrine, collagen, ristocetin, arachidonic acid, serotonin, LPS and thrombin. Heparanase levels were assessed by ELISA, heparanase procoagulant activity assay and western blot analysis. The effects of selective protease-activated receptor (PAR)-1 and 2 inhibitors and PAR-1 and 4 activators were studied. An in-house synthesised inhibitory peptide to heparanase was used to evaluate platelet heparanase involvement in activation of the coagulation system. Heparanase was released from platelets only by thrombin induction while other inducers exerted no such effect. The heparanase level in a platelet was found to be 40 % higher than in a granulocyte. Heparanase released from platelets or granulocytes increased factor Xa generation by three-fold. PAR-1 activation via ERK intracellular pathway was found to induce heparanase release. In conclusion, heparanase is selectively released from platelets and granulocytes by thrombin interacting with PAR-1. Heparanase derived from platelets and granulocytes is involved in activation of the extrinsic coagulation pathway. The present study implies on a potential anticoagulant effect, in addition to anti-platelet effect, of the new clinically studied PAR-1 inhibitors.

Preimplantation genetic diagnosis for fetal neonatal alloimmune thrombocytopenia due to antihuman platelet antigen maternal antibodies.

OBJECTIVE: To develop a reliable preimplantation genetic diagnosis protocol for antihuman platelet antigen-1 incompatibility for a family in whom antenatal treatment was not possible because of the mother's hypersensitivity to intravenous immunoglobulin (IVIG). METHODS: Haplotypes were constructed from genomic DNA of the family members. A polymerase chain reaction protocol that included eight microsatellite polymorphic markers and the ITGB3-specific (T196C, rs5918) polymorphism were multiplexed to be used in a single cell protocol, and single blastomeres were analyzed. RESULTS: In one preimplantation genetic diagnosis cycle, out of 28 retrieved oocytes, 24 embryos fertilized and 12 underwent biopsy. Three embryos were found to be antihuman platelet antigen-1b/1b homozygotes and two were transferred. This cycle resulted in an uneventful pregnancy and birth of a healthy child. CONCLUSION: In cases in which there is antihuman platelet antigen incompatibility and IVIG cannot be administered, preimplantation genetic diagnosis is a reliable alternative to enable birth of unaffected children.

Tyrosine kinase inhibitors induced immune thrombocytopenia in chronic myeloid leukemia?

The outcome and quality of life of chronic myeloid leukemia (CML) patients has remarkably changed with the treatment of tyrosine kinase inhibitors (TKIs). Currently, hematopoietic stem cell transplantation (HSCT) is considered mainly as a third line salvage therapy in cases of TKIs resistance or intolerance. Here we describe a patient with chronic phase CML who developed both resistance and late occurrence of s severe thrombo-cytopenia on first and second generation TKIs and eventually underwent HSCT. Although the mechanism of the myelosuppression is not fully understood, we showed for the first time the development of dose dependent platelet antibodies in the presence of TKIs, suggesting the possibility of TKIs induced thrombocytopenia. Our case emphasizes that late development of severe myelosuppression during imatinib treatment is probably an important indication for consideration of early HSCT.