BENIGN FAMILIAL MICROCYTIC THROMBOCYTOSIS WITH AUTOSOMAL-DOMINANT TRANSMISSION

Familial thrombocytosis is an extremely rare disorder, so far reported in only a handful of families. In the majority of cases the character istics were of essential thrombocythemia. Most patients presented with a platelet count above 800 000/mm(3), were diagnosed as having a myel oproliferative disease, and some required chemotherapy. We describe a benign form of familial thrombocytosis with autosomal dominant inherit ance in five healthy members of three generations of a family, all of whom had moderate thrombocytosis within the range 422 000-662 000/mm(3 ), characterized by low mean platelet volume. A careful medical histor y and a 5-year follow up of the subjects did not reveal any untoward c linical development. This variant of familial thrombocytosis is theref ore of a benign nature. Possible mechanisms linking thrombocytosis wit h platelet microcytosis in this family are discussed.