Hemolytic uremic syndrome in children: platelet aggregation and membrane glycoproteins.

PURPOSE: Several mechanisms have been proposed to explain the fibrin-platelet thrombosis at the microcirculation level in the different clinical conditions of hemolytic uremic syndrome (HUS). The relationships between platelet structure and function during the first 4 weeks of evolution of the disease were studied to understand the mechanism of platelet alteration. PATIENTS AND METHODS: Coagulation parameters, platelet counts, and aggregation were studied in 49 children, and membrane glycoproteins (GPs) in 20 of the 49 children (mean age, 17 months) with HUS (Group 2) were studied during the first 4 weeks of evolution of the disease. RESULTS: No disseminated intravascular coagulation was found in patients with recurrent or persistent thrombocytopenia. Platelet aggregation was sequentially performed during the first weeks of evolution. All patients had a functional decrease in the acute period of HUS. Platelet GPs GPIb, GPIIbIIIa, GPIIb, and GPIIIa were evaluated. GPIIbIIIa complex presented low level and never reached normal values during the first 4 weeks of disease. CONCLUSIONS: Platelet alterations are probably caused by multiple mechanisms: "exhausted" platelets, structural membrane alterations caused by arginine-glycine-aspartic peptide blockade, or diminished or nonfunctional membrane GPIb and GPIIbIIIa complexes.

Glanzmann thrombasthenia in children from Argentina.

PURPOSE: Glanzmann thrombasthenia is a well-defined inherited disorder of platelet function characterized by a decrease or absence of functional platelet glycoprotein (GP) GPIIbIIIa. The diagnosis must be considered in patients presenting with mucocutaneous bleeding, purpura, a normal platelet count, abnormal platelet aggregation, and a prolonged bleeding time. In most of the patients, the presence of small amounts of either GPIIb or GPIIIa was detected in their platelets. These observations could provide a basis for determining the clinical and laboratory heterogeneity of the disease. PATIENTS AND METHODS: We studied 10 patients of seven unrelated families with the usual methods and an immunoalkaline phosphatase technique (APAAP) to analyze the biosynthesis of GP in megakaryocytes. RESULTS: The results allowed us to classify six patients as GT type I, three as type II, and one as a variant. CONCLUSION: The nature and severity of the bleeding manifestations, in our patients, were not predictible by the laboratory findings. These confirm the clinical and laboratory heterogeneity of the disease.