Grey platelet syndrome: evidence for alpha-granule localization of the platelet plasminogen activator inhibitor-1 pool.

The case of an 11-year-old boy with grey platelet syndrome is described. Platelets had the typical grey and ghostly appearance on May-Grünwald/Giemsa staining, caused by the absence of alpha granules confirmed by electron microscopy. Alpha granule protein content, i.e., beta-thromboglobulin and platelet factor 4, was less than 3% of normal and alpha granule secretion in response to thrombin was not detectable photometrically. The plasminogen activator inhibitor-1 pool in the patient's platelets was 5% of normal, confirming previous indirect evidence for the storage of this protein within the alpha-granule. Dense body secretion of adenosine triphosphate and 5-hydroxytryptamine was normal. Aggregation occurred normally in response to adenosine diphosphate and there was a slight delay in response to collagen.     

The thrombopoietin level in the cord blood in premature infants born to mothers with pregnancy-induced hypertension

OBJECTIVE: To investigate the level of thrombopoietin in the cord blood of preterm infants, and its relationship with neonatal platelet count and pregnancy-induced hypertension. STUDY METHOD: Thrombopoietin levels in the cord blood of preterm neonates, with or without maternal pregnancy-induced hypertension, were measured by enzmye-linked immunosorbent assay. RESULTS: The platelet count was significantly lower in very low birth weight infants, infants with maternal pregnancy-induced hypertension, and infants with maternal thrombocytopenia. Neonatal thrombocytopenia was associated with maternal pregnancy-induced hypertension and very low birth weight. The neonatal platelet count was correlated significantly with the birth weight and the maternal platelet count. There was no difference in the cord blood level of thrombopoietin between infants born to mothers with pregnancy-induced hypertension and those without. No correlation was found between the thrombopoietin level and the neonatal platelet count. A positive correlation between the cord blood thrombopoietin and the maternal platelet count was identified. CONCLUSIONS: Maternal pregnancy-induced hypertension and very low birth weight were significantly associated with thrombocytopenia in premature infants, which cannot be explained by decreased thrombopoietin level.     

Intratumoral consumption of indium-111-labeled platelets in a child with splenic hemangioma and thrombocytopenia

The authors report Kasabach-Merritt syndrome (KMS) in a patient with thrombocytopenia and splenic hemangioma. A 13-month-old boy with a history of anemia, thrombocytopenia, and abdominal mass was admitted to the hospital. The scintigraphic studies showed that a large mass contiguous to the spleen was responsible for the platelet uptake. After partial splenectomy, the platelet count returned to normal. This report of KMS in a child with splenic hemangioma suggests that the scintigraphic studies are mandatory to confirm diagnosis. Indium-111-labeled platelets are useful in identifying hemangiomatous sequestration of platelets in patients with thrombocytopenia.     

Alpha-interferon therapy induces improvement of platelet counts in children with chronic idiopathic thrombocytopenic purpura

PURPOSE: To investigate alpha-interferon (IFN) therapy for children with chronic idiopathic thrombocytopenic purpura (ITP). PATIENTS AND METHODS: Patients with refractory ITP lasting more than 12 months from diagnosis were included if they had platelet counts <50 x 10(9)/L and had received no treatment during the past month. Patients received IFN (3 x 10(6) U/m2 per dose), three times per week for 4 weeks; if partial (<150 x 10(9)/L) or no response was obtained, the same dose was continued for another 8 weeks. In patients with favorable response and subsequent decrease to pre-treatment values, an additional 4 weeks of treatment could be administered. RESULTS: Fourteen patients (ages 4-20 y) receiving 17 IFN courses were included. Mean initial platelet count was 29 +/- 15 x 10(9)/L. A significant increase was achieved during 14 of 17 courses (82.4%). All but two responses were transitory, and platelets returned to initial values after IFN discontinuation (mean 44 +/- 26 days). Considering the best response achieved by each patient, we observed: 1) 10 patients who achieved a sustained improvement of platelet count throughout the treatment period, decreasing to initial values after therapy was stopped; 2) one patient who achieved platelet count >150 x 10(9)/L, remaining with normal platelets at 18 months; 3) one patient who achieved platelet count >150 x 10(9)/L, remaining with platelets between 100 and 140 x 10(9)/L at 48 months; 4) one patient who had no response; and 5) one patient in whom therapy worsened the thrombocytopenia. A mild to moderate flu-like syndrome and a moderate decrease of the absolute neutrophil count were the only side effects observed. CONCLUSION: Interferon therapy induces a significant increase of platelet count and seems to be a valid alternative therapy to attempt the achievement of prolonged remission in refractory ITP, to defer splenectomy in younger children, or to improve platelet count before planned splenectomy.     

Reticulated platelet counts in the assessment of thrombocytopenic disorders

Reticulated platelets (RP) are the youngest platelets in the circulation and can be measured by analysing the RNA content of platelets from whole blood or platelet-rich plasma by flow cytometry. Increased RP are indicative of increased production of platelets. Despite the current lack of standardization for the measurement of RP, it is useful in the assessment of patients with ITP by aiding the distinction of these patients from those with decreased platelet production. RP counts also have a role in the assessment of the complicated patient with multiple possible aetiologies for thrombocytopenia. Measurement of the RP count may hold predictive value for marrow recovery following myelosuppressive or myeloablative chemotherapy, and may play a role in monitoring the administration of the various thrombopoietins currently under clinical trial.     

Juvenile cyclic amegakaryocytic thrombocytopenia: a novel entity

Cyclic thrombocytopenia is a rare disorder described in adults, characterized by periodic platelet count fluctuations of unknown etiology. The authors describe a boy with cyclic changes in platelet counts ranging from 2 x 10(9)/L to 224 x 10(9)/L with a periodicity of 25 days. Since birth, the patient had periods of bruising. Platelet counts were periodically low during these periods. Thrombopoietin plasma levels oscillated inversely with the platelet count, whereas glycocalicin levels oscillated in phase with the platelets. No oscillation was seen in neutrophil and reticulocyte numbers. The bone marrow showed periodic reduction in megakaryocyte counts. In an in vitro megakaryocytopoiesis assay, the patient's CD34+ cells showed megakaryocyte formation, although to a lower level than controls. Addition of patient plasma, collected during the rise in platelet numbers, to cultures with normal bone marrow-derived CD34+ cells caused an increase in the development of CD41+ megakaryoblasts. Because the periods with bruising had existed since birth, apparently this is a form of congenital cyclic thrombocytopenia. The underlying mechanism of the cyclic thrombocytopenia in this patient is not yet clear, and until now, no therapy has been found for this patient. However, platelet transfusions have resulted in cessation of bleeding during thrombocytopenic periods.     

Misdiagnosis of chronic thrombocytopenia in childhood

PURPOSE: Children ultimately diagnosed with nonimmune chronic thrombocytopenia are often referred to pediatric hematology clinics with a provisional diagnosis of autoimmune thrombocytopenic purpura (AITP). The authors' aim was to establish in these patients the features characterizing the mechanism of thrombocytopenia. PATIENTS AND METHODS: The authors performed a retrospective review of the case records of seven children (three boys and four girls, aged 5 months to 7 years) with misdiagnosed chronic AITP referred to a single pediatric hematology center between 1990 and 2000. RESULTS: In the seven children, the suspected diagnosis on referral was AITP and the final diagnosis was inherited thrombocytopenia. Abnormalities of platelets and/or leukocyte morphology were present in all of them. Other features suggestive of inherited thrombocytopenia included a history of familial thrombocytopenia (2/7), failure of steroids and/or intravenous immunoglobulins to raise the platelet count to normal levels (5/7), and moderate increase of Indium-111 platelet turnover in the two patients tested. Platelet-associated IgG (PaIgG) was above the normal threshold in the four children tested; the direct monoclonal antibody immobilization of platelet antigens (MAIPA) test was negative in the four children tested and the serum test was positive in two boys. Bone marrow examination revealed either a normal (4/7) or an elevated (3/7) number of megakaryocytes. CONCLUSIONS: Family history and blood cell morphology analysis in experienced hands are the first steps in discriminating AITP from inherited thrombocytopenia in children with isolated chronic thrombocytopenia. In contrast, bone marrow examination and search for specific autoantibodies using the MAIPA test are of little help. An isotopic platelet life span study, when available, should be performed before considering splenectomy to exclude the diagnosis of inherited thrombocytopenia, especially when steroids and/or IgG IV administration failed to raise the platelet count.     

The significance of ABO-incompatibility on umbilical cord platelets

ABO-incompatibility has been proposed as a cause of neonatal thrombocytopenia. We conducted a study in 1982 of 172 deliveries at Odense University Hospital. We investigated umbilical cord blood in all cases and compared ABO-compatible groups with ABO-incompatible groups. No statistically significant difference in platelet counts or number of thrombo-cytopenic neonates was found. In four detected cases with immune anti-A antibody, no influence on platelet count could be observed, and in the cases with hyperbilirubinaemia during the first 24 h no influence of ABO-incompatibility could be demonstrated either. With the platelet suspension immunofluorescence test, A and B antigens were demonstrated on adult platelets and A antigen on umbilical cord platelets. A slight elevated level of PlIgG was detected on umbilical cord platelets in six samples (3.4%). It seemed that PlIgG correlated with the content of anti-A and anti-B IgG in maternal serum, but did not correlate with a reduction in platelet count, hyperbilirubinaemia or HLA-antibodies. A pathogenetic influence of ABO-incompatibility on umbilical cord platelets could not be detected in this study.     

Isolated thrombocytopenia in children with acute lymphoblastic leukemia: a rare event in a Pediatric Oncology Group Study

To determine how many children with acute lymphoblastic leukemia were initially referred to a pediatric hematologist because of isolated significant thrombocytopenia ([platelet count less than 50,000/mm3] and an otherwise normal complete blood cell count and physical findings), a retrospective review of the Pediatric Oncology Group's charts was undertaken. Review of the records of 2239 children enrolled in the past two acute lymphoblastic leukemia protocols showed that none of these children had significant thrombocytopenia with no other hematologic or physical manifestations of acute lymphoblastic leukemia when they were first seen by the hematologist. The results suggest that routine bone marrow aspiration in the child with isolated thrombocytopenia may be unnecessary to rule out acute lymphocytic leukemia.     

Transfusion-associated fall in platelet count in very low birthweight infants

Thirty-three infants with a birthweight of less than 1500 g were investigated retrospectively for the incidence and aetiology of thrombocytopenia occurring during the first week of life. The platelet count fell below 100 x 10(9)/l in 16 infants (48%). There was a moderately strong inverse correlation between the platelet count at its nadir during the first week or the first value below 100 x 10(9)/l and the percentage of blood volume transfused prior to this (r = -0.61; P less than 0.0001). When the platelet count was expressed as a percentage of the initial count the correlation was -0.74 (P less than 0.0001). The results were not affected by the elimination of the 10 infants with clinical conditions regarded as a probable cause of thrombocytopenia. The fitted least-squares regression line suggests that a transfusion equal to 10% of the blood volume on average reduced the platelet count by 19 x 10(9)/l or by 7% in these very low birthweight infants during the first week of life.     

Upshaw-Schulman Syndrome in Two Siblings

Upshaw-Schulman syndrome is a rare disease, and familial occurrence has not been reported. In this paper, two Japanese brothers, aged 2 and 6 years, with microangiopathic hemolytic anemia, thrombocytopenia and fragmented red cells from the newborn period are reported. Unusually large von Willebrand factor (vWF) multimers were found in the plasma samples from both cases during remission, while the quantities of the unusually large vWF multimers decreased greatly at a low platelet count. They were temporarily relieved from hemolytic anemia and thrombocytopenia by infusions of plasma from normal donors. It appears that our patients lack an unidentified plasma factor, which is genetically determined.     

Fetal and neonatal thrombopoietin levels in alloimmune thrombocytopenia

Thrombopoietin (Tpo) is the main hematopoietic growth factor for platelet production. Plasma Tpo levels in autoimmune thrombocytopenic patients are normal or slightly elevated. Although thrombocytopenia exists, Tpo levels are not increased because the produced megakaryocytes and platelets can bind circulating Tpo, thereby normalizing Tpo levels. In this study, plasma samples from fetuses and neonates with neonatal alloimmune thrombocytopenia (NAIT), a different form of immune thrombocytopenia, were measured. Umbilical cord samples from 50 fetuses before treatment because of severe thrombocytopenia and 51 fetuses after treatment, and peripheral blood samples of 21 untreated newborns with NAIT were analyzed. As controls, plasma Tpo levels were determined in 21 umbilical cord samples of 14 nonthrombocytopenic fetuses with hemolytic disease resulting from red blood cell alloimmunization and in umbilical cord samples of 51 healthy newborns. The values were also compared with the plasma Tpo levels in 193 healthy adults. Mean Tpo levels from the groups of fetuses and neonates, including both NAIT and control plasma, were slightly but significantly elevated compared with levels in healthy adults. Tpo levels in NAIT samples were not significantly different from the levels in hemolytic disease samples or in samples from healthy newborns. Thus, as in autoimmune thrombocytopenic patients, normal Tpo levels are present in NAIT patients.     

Kasabach-Merritt syndrome: therapeutic considerations

During the past 15 years we have managed six children with capillary hemangiomas in association with consumptive coagulopathy--the Kasabach-Merritt syndrome. Their ages when first seen ranged from 2 weeks to 4 years with a mean of 19 months. In three of the patients, the hemangiomas remained small for many months and then suddenly enlarged and hemorrhagic diatheses appeared. The duration of the thrombocytopenia ranged from 5 to 20 months, a time span that in some of the patients was influenced by the type of treatment used. Each patient received a variety of therapies including the following: medications to control the coagulopathy; mechanical, cytolytic, and pharmacologic treatment to eradicate the lesion; and blood product support with platelets and cryoprecipitate for severe bleeding. A prompt elevation of the platelet count occurred in three of the patients after the lesion was biopsied. Subtotal resection of the lesion resulted in an immediate increase of the platelet count in one patient. A transient increase in platelet counts and fibrinogen levels was observed in another patient following several embolizations of a portion of the hemangioma. Other modes of therapy were difficult to evaluate, especially because the same therapy applied at different times in the same patient effected a different type of response. Eventually, all of the patients experienced resolution of their lesions and, with this, concomitant reversal of the coagulopathy.     

Transfusion-associated fall in platelet count in very low birthweight infants

Abstract Thirty-three infants with a birthweight of less than 1500 g were investigated retrospectively for the incidence and aetiology of thrombocytopenia occurring during the first week of life. The platelet count fell below 100 × 10⁹/l in 16 infants (48%). There was a moderately strong inverse correlation between the platelet count at its nadir during the first week or the first value below 100 × 10⁹/l and the percentage of blood volume transfused prior to this ( r =−0.61; P < 0.0001). When the platelet count was expressed as a percentage of the initial count the correlation was −0.74 ( P < 0.0001). The results were not affected by the elimination of the 10 infants with clinical conditions regarded as a probable cause of thrombocytopenia. The fitted least-squares regression line suggests that a transfusion equal to 10% of the blood volume on average reduced the platelet count by 19 × 10⁹/l or by 7% in these very low birthweight infants during the first week of life.     

MYH9 related platelet disorders - often unknown and misdiagnosed

MYH9 related platelet disorders are a relatively rare cause of thrombocytopenia. Located on chromosome 22, the MYH9 gene encodes the motorprotein non-muscular myosin heavy chain IIA (NMMHCIIA). Heterozygous defects in this gene lead to 4 different autosomal dominant syndromes namely May-Hegglin anomaly, Epstein syndrome, Fechtner syndrome and Sebastian platelet syndrome. All 4 syndromes are characterized by macrothrombocytopenia and a mild bleeding tendency. Depending on the position of the causative mutation within the gene, the risk increases for syndromic manifestations such as renal failure, hearing loss and pre-senile cataract. Mutations in the neck region of the NMMHCIIA protein are more likely associated with these comorbidities than mutations in the N- or C-terminal part of the gene. MYH9 related platelet disorders should be excluded in patients with chronic thrombocytopenia and large platelets. Most sensitive for diagnosis/exclusion are immunofluorescence studies using a blood smear. The biggest risk for these patients is ineffective but potentially harmful treatment based on the misdiagnosis of immune thrombocytopenia. This review provides a workflow for diagnosis and treatment of MYH9 related thrombocytopenia.     

Hemostasis in Glanzmann's thrombasthenia (GT): GT platelets interfere with the aggregation of normal platelets

The transfusion requirements for a 6-year-old Glanzmann's thrombasthenia (GT) patient undergoing tonsillectomy and adenoidectomy were studied. Transfusion of pheresed platelets from a single normal donor increased the platelet count by 63 x 10(9)/L but did not correct the bleeding time. Since the ratio of normal:GT platelets in vivo was approximately 1:5, it was possible that GT platelets interfered with the function of normal platelets. To test this hypothesis, mixtures of platelet-rich plasma (PRP) from a normal donor and the patient were studied to determine a ratio of normal:GT platelets that would yield acceptable in vitro aggregation. Normal:GT ratios of 1:4 and 3:2 resulted in 25% and 59% aggregation, respectively. Mixtures of normal and nonfunctional ethylene glycol tetra-acetic acid-treated platelets gave similar results. Aggregates from mixtures of normal and patient platelets were also examined morphologically by light microscopy and were proportional in size to the normal:GT platelet ratio. Transfusion of platelets from the pheresis of four donors increased the patient's platelet count by greater than 300 x 10(9)/L (normal:GT ratio 1:1), produced 53% aggregation, and resulted in satisfactory postoperative hemostasis. The platelet transfusion requirement for this GT patient was much greater than would have been expected in the absence of aggregation-defective platelets.     

Neonatal thrombocytopenia: what we do and don't know

The evaluation and management of thrombocytopenia is a frequent challenge for neonatologists, as it affects 22-35% of infants admitted to the neonatal intensive care unit. Multiple disease processes can cause neonatal thrombocytopenia, and these can be classified as those inducing early thrombocytopenia (72 h). Most cases of neonatal thrombocytopenia are mild to moderate, and do not warrant intervention. In approximately 25% of affected neonates, however, the platelets count is <50x10(9)/L, and therapy with platelet transfusions is considered to decrease the risk of hemorrhage. The existing evidence to establish platelet transfusion triggers in neonates is very limited, but it suggests that transfusing platelets to non-bleeding neonates with platelet counts >50x10(9)/L does not decrease the risk of intraventricular hemorrhage (IVH), and that 30x10(9)/L might be an adequate threshold for stable non-bleeding neonates. However, adequately powered multi-center studies are needed to conclusively establish the safety of any given set of neonatal transfusion guidelines.     

Increase in platelet count is not affected by the platelet yield of single donor pheresed platelets

OBJECTIVES: To determine if the rise in platelet count after transfusion in neonates is associated with platelet yield of the pheresed platelet unit. STUDY DESIGN: Cohort study of infants in a level 3 Neonatal Intensive Care Unit that received single donor platelets (SDP). Platelet rise in infants were compared between 3 groups: underproduction, destruction, and idiopathic. The main outcome variable studied was the rise in platelet count posttransfusion. Statistical analysis included analysis of variance, Pearson correlation, and multivariate linear regression. RESULTS: The gestational age was 28+/-4.5 weeks. The platelet yield was 4.2+/-0.7 (x10(11)) and resultant platelet rise was 71+/-58.6x1000/mm3. Infants with platelet underproduction (n=30) had a greater rise compared with infants with platelet destruction (n=51) after transfusion (95.3+/-58 vs. 59.6+/-57.5x1000/mm3, P=0.01). After controlling for confounding variables, there was no correlation between the platelet yield and platelet rise, but the etiology of the thrombocytopenia remained associated with increased platelet rise. CONCLUSIONS: There was no association between platelet yield of SDP and platelet rise. Infants with thrombocytopenia related to platelet underproduction had a greater rise in platelets after transfusion compared with those with platelet destruction, independent of yield or volume of the SDP transfusion.     

Neonatale Thrombozytopenie

Thrombocytopenia is the most common hematological abnormality in the investigation of the blood picture of preterm and term neonates. For the initial evaluation of thrombocytopenia five criteria are very useful. (1) Onset within 72?h after birth (early onset vs. late onset beginning >72h after birth), (2) clinically ill vs. otherwise healthy neonate, (3) the severity (<50??×?10⁹/l) and kinetics of thrombocytopenia (reduction in platelet numbers of >50??×?10⁹/l per day), (4) the likelihood of a maternal/placental or a fetal/neonatal cause and (5) dysmorphic stigmata or malformations as indications for a systemic disorder. If thrombocytopenia persists longer than 10 days specific diagnostics are recommended, including the analysis of platelet morphology, measurement of the immature platelet fraction (IPV) and/or of the mean platelet volume (MPV) and the measurement of transaminases. The individual risk of bleeding depends not only on the cause of thrombocytopenia but also on the specific biology of fetal/neonatal platelets as well as on the plasmatic coagulation system and the vascular endothelium. As controlled trials have not provided any evidence that prophylactic platelet transfusion reduces the risk of bleeding in neonates without primary hematological or immunological causes of thrombocytopenia, restrictive platelet transfusion thresholds have become established in non-bleeding neonates.