Thrombocytopaenia: a serious side effect of diazoxide.

A 2.5-year-old boy with a history of (transient) congenital hyperinsulinism was admitted to the paediatric ward with recurrent hypoglycaemia. Diazoxide 5 mg/kg/day and hydrochlorothiazide 2 mg/kg/day were initiated. After increasing the dose of diazoxide to 10 mg/kg/day, the child developed mild rectal bleeding, petechiae, epistaxis and haematemesis. Blood screening showed severe thrombocytopaenia. Diazoxide and hydrochlorothiazide were stopped, and his platelet count normalised. Drug rechallenge was positive. Drug-induced immune thrombocytopaenia was diagnosed.