We describe an autosomal dominant hereditary thrombocytopenia syndrome caused by a defect in the MYH9 gene. Of our three patients, all have thrombocytopenia from birth, and their thrombocytes are large in size. The hemorrhagic tendency caused by thrombocytopenia is often mild. Approximately 60% of the patients develop sensorineural hearing loss and approx. 30% develop renal insufficiency that frequently progresses to require hemodialysis. It is of particular importance to recognize the thrombocytopenia as being hereditary and permanent in order to save the patients from useless and harmful therapeutic efforts.