Occult quinine-induced thrombocytopenia.

Quinine is universally used for the very common symptom of night leg cramps. Patients may not mention it among their medicines, since it is so commonly used and they regulate it themselves. A 68-year-old man suddenly developed extensive bleeding due to severe thrombocytopenia. The diagnosis was initially thought to be a recurrence of idiopathic thrombocytopenic purpura (ITP) that had initially occurred in 1992 and had required splenectomy. Drug-induced thrombocytopenia was also considered, and he was told to stop all of his medicines. Only after three subsequent episodes of severe, symptomatic thrombocytopenia over the next four weeks did he say, upon repeat questioning, that he had continued to take quinine for night leg cramps. Even after a strict warning, he took another quinine tablet that evening, which triggered his fifth episode of severe thrombocytopenia, and confirmed the etiology of quinine-induced thrombocytopenia. The diagnosis thrombocytopenia caused by common drugs can be difficult, requiring persistent, explicit questions.