Hereditary thrombocytopenias in childhood.

Thrombocytopenia is generally known in its most severe form as acquired immunologic disease. However, in some cases thrombocytopenia is constitutional and may or may not be associated with thrombocytopathy. This review focuses on the clinical and biologic diagnostic criteria of genetic thrombocytopenia, with specific emphasis on the clinical value of the platelet life span and wishes to reiterate the necessity of their identification, as an excessively rapid diagnosis of ITP may be a source of treatment failure. As an example of constitutional thrombocytopenia, we report here 83 familial cases with pure genetic macrothrombocytopenia. They are characterized by the absence of significant bleeding disorders, stable thrombocyte counts higher than 50 x 10(9)/l, platelet macrocytosis, normal platelet function, normal or never increased presence of megakaryocytes, and rarely positive immunological abnormalities. In all cases, platelet life span clearly indicated a defect of production with destruction linked to the ageing population (more than 7 days) and no abnormal sequestration in the spleen or liver. Thus, apart from thrombocytopenia with thrombocytopathy, kinetic studies are necessary in thrombocytopenias whenever clinical parameters do not suggest the presence of excessive platelet destruction.