A NOVEL HEREDITARY MACROTHROMBOCYTOPENIA

Purpose: A family is described in which macrothrombocytopenia and hear ing loss are transmitted in an autosomal-dominant fashion. Patients an d Methods: Several members of the family were studied extensively. Rev iew of blood smears, coagulation studies, platelet function testing, a nd electron microscopy were performed. Platelet membrane glycoproteins were examined using flourescein-conjugated antibodies and flow cytome try. Results: Platelet counts ranged from 50,000 to 123,000/mu l. Both mean platelet diameter and volume were increased. No leukocyte inclus ions were noted by light or electron microscopy. Platelet aggregation was normal with adenosine diphosphate (ADP), collagen, and ristocetin but diminished with epinephrine and arachidonic acid. Flow cytometry s howed normal platelet membrane glycoproteins and the unusual expressio n of glycophorin A on 40-60% of the giant platelets. Conclusions: This family's syndrome of macrothrombocytopenia and late-onset hearing los s appears to represent a novel giant platelet disorder. The expression of glycophorin A suggests disordered megakaryocytopoiesis with the ea rly release of immature platelets.