Benign familial thrombocytosis

A 13-year-old girl was found to have a platelet count in excess of 4 million/microliters while being evaluated for a minor bleeding episode. Her father and two sisters also had thrombocytosis. All four affected patients were asymptomatic and had no clinical or laboratory evidence of a myeloproliferative disorder other than an elevated platelet count. This represents the second reported instance of benign familial thrombocytosis.