An incidental finding of extreme self-limited thrombocytosis of unknown cause.

This report describes an 11-year-old male who presented to his pediatrician at the Bowman Gray School of Medicine in Winston-Salem, N.C., because of long standing enuresis. During evaluation and the following two-week period, this patient was found to have extreme thrombocytosis ranging from 2,175 x 10(9)/L to 3,700 x 10(9)/L. In the absence of any apparent reactive cause, a presumptive diagnosis of essential thrombocythemia was made. Although chemotherapy was considered, the patient was temporarily lost to follow-up before there was a final decision about therapy. One year later, this patient's platelet count had spontaneously decreased to normal (273 x 10(9)/L), and has remained normal during a follow-up period of seven years, although only sporadic platelet counts have been obtained. His most recent physical examination revealed no abnormalities. The case is presented as further evidence that extremely high platelet counts are not necessarily dangerous and do not all require therapy.