Primary thrombophilia in Mexico IX: the glycoprotein IIIa PLA1/A2 polymorphism is not associated with the sticky platelet syndrome phenotype.

INTRODUCTION: The sticky platelet syndrome (SPS) seems to be a common cause of thrombosis, although no molecular substrate to explain platelet hyperaggregability has been found. OBJECTIVE: To analyze an association between the SPS phenotype and the platelet glycoprotein (GP) IIIa PL(A1/A2) (human platelet antigen [HPA]-1a/b) gene polymorphism. METHODS: Along an 18-month period, Mexican mestizo thrombophilic patients were prospectively accrued. The SPS phenotype was assessed by aggregometry, whereas a tetra-primer amplification refractory mutation system (ARMS) polymerase chain reaction analysis was used to detect the PLA1 and PLA2 alleles. RESULTS: A total of 95 individuals with SPS and 127 healthy donors were studied; in 11 of the donors and 16 of the patients with SPS the A2 allele of the GP IIb/IIIA was found, yielding a weak and nonsignificant association (odds ratio 2.14, 95% CI 0.94-4.85). CONCLUSION: In Mexican mestizo patients, the platelet GP IIIa PL(A1/A2) gene polymorphism does not lead to the SPS phenotype.

Platelet dysfunction-eosinophilia syndrome in parasitized Venezuelan children.

Platelet dysfunction was detected in six children with purpura and eosinophilia. We conducted clinical evaluations, hematologic and platelet function tests, clotting studies (bleeding time, prothrombin time, partial thromboplastin time, thrombin time, factor XIII, factor VIII, and von Willebrand factor), assays for IgG and IgM antibodies to platelets, and a search for stool parasites. Mild bleeding phenomena (ecchymoses, petechiae, epistaxis, and gingival) were transient. All children showed intestinal parasites and marked eosinophilia (mean count = 2,615.2 cells/muL, 95% confidence interval = 1,259.6-5,429.8). Main abnormalities included prolonged bleeding times (50%) and defective aggregation with collagen (100%) adrenaline (66%), or ADP (66%). Antibodies to platelets were not detected. Anti-parasite therapy reversed the hemorrhagic manifestations and normalized eosinophil counts and platelet alterations. No relationship could be established between excess eosinophils, intensity of bleeding, or type and degree of platelet abnormalities. Thrombocytopathic features mimicked the intrinsic defect of storage pool disease. The possible pathogenic roles of eosinophilia and parasitism are reviewed. This is the first report of this pathologic combination in Latin American children.

Sebastian syndrome: report of the first case in a South American family.

The Sebastian syndrome (SS) is a MYH9-related disorders, which are an extremely infrequent group of four autosomal dominant illnesses. SS consist of giant platelets, leukocyte inclusions and thrombocytopenia. To our knowledge, there are no case reports of this syndrome in South America. The propositus was a 35-year-old Argentine woman with a history of purpuric lesions in her lower limbs and thrombocytopenia. Idiopathic thrombocytopenia purpura (ITP) was previously diagnosed, but she did not respond to treatment with steroids. Family history failed to provide any evidence of hearing loss, easy bruising, nephritis, renal failure or cataracts. The patient and 11 members of her family were evaluated. The diagnosis of SS was established by demonstrating giant platelets, thrombocytopenia and leukocyte inclusions in peripheral smear in two relatives and by peripheral smear and electronic microscopy in the propositus. MYH9-related disorders should be suspected whenever a patient has a low platelet count or a bleeding diathesis of unknown origin. In these cases, the history, carefully peripheral smear exam, immunocytochemistry and electronic microscopy will be of great help. Differentiation ITP with SS is important to avoid unnecessary diagnostic studies and treatments.

Reticulated platelet values in normal and thrombocytopenic neonates.

OBJECTIVES: Reticulated platelets (RPs) are newly synthesized platelets with increased ribonucleic acid content. The percentage of RPs is elevated in adults with thrombocytopenia as a result of increased platelet destruction. The objectives of this study were to determine normal RP values in neonates at birth and to determine whether neonates with thrombocytopenia as a result of increased platelet destruction have an increased percentage of RPs. STUDY DESIGN: The RP percentages were measured at birth in 89 neonates without thrombocytopenia in three gestational age groups (<30,30 to 36, and >36 weeks), six neonates with immune thrombocytopenia, and one neonate with thrombocytopenia as a result of decreased platelet production. RESULTS: The RP percentages in neonates without thrombocytopenia >36 weeks and 30 to 36 weeks of gestation were 4.0% +/- 2.4% (mean +/- SD) and 4.6% +/- 1.7%, respectively, similar to values reported in healthy adults. Neonates younger than 30 weeks of gestation had significantly higher RP percentages (8.8% +/- 5.1%) than older neonates (p

Impaired cytoplasmic ionized calcium mobilization in inherited platelet secretion defects.

Defects in platelet cytoplasmic Ca++ mobilization have been postulated but not well demonstrated in patients with inherited platelet secretion defects. We describe studies in a 42-year-old white woman, referred for evaluation of easy bruising, and her 23-year-old son. In both subjects, aggregation and 14C-serotonin secretion responses in platelet-rich plasma (PRP) to adenosine diphosphate (ADP), epinephrine, platelet activating factor (PAF), arachidonic acid (AA), U46619, and ionophore A23187 were markedly impaired. Platelet ADP and adenosine triphosphate (ATP), contents and thromboxane synthesis induced by thrombin and AA were normal. In quin2-loaded platelets, the basal intracellular Ca++ concentration, [Ca++]i, was normal; however, peak [Ca++]i measured in the presence of 1 mmol/L external Ca++ was consistently diminished following activation with ADP (25 mumol/L), PAF (20 mumol/L), collagen (5 micrograms/mL), U46619 (1 mumol/L), and thrombin (0.05 to 0.5 U/mL). In aequorin-loaded platelets, the peak [Ca++]i studied following thrombin (0.05 and 0.5 U/mL) stimulation was diminished. Myosin light chain phosphorylation following thrombin (0.05 to 0.5 U/mL) stimulation was comparable with that in the normal controls, while with ADP (25 mumol/L) it was more strikingly impaired in the propositus. We provide direct evidence that at least in some patients with inherited platelet secretion defects, agonist-induced Ca++ mobilization is impaired. This may be related to defects in phospholipase C activation. These patients provide a unique opportunity to obtain new insights into Ca++ mobilization in platelets.