The first Japanese family with Sebastian platelet syndrome.

This report describes the first Japanese family diagnosed with Sebastian platelet syndrome. Within this family, a 6-year-old boy and 3 family members on his paternal side demonstrated thrombocytopenia with giant platelets and inclusion bodies in granulocytes, but the additional clinical features of Alport's syndrome occurring in the Fechtner syndrome were lacking. Light microscopy and ultrastructural findings of the leukocyte inclusion bodies distinguished these patients from the May-Hegglin anomaly. This family showed consistently higher levels of platelet-associated IgG (PAIgG), while surface expression of platelet membrane glycoproteins (GPIIb/IIIa and GPIb) and plasma glycocalicin levels were within the normal range. Careful observation of the giant platelet and leukocyte inclusion bodies in blood smears may help the diagnosis of this rare disease entity.