Cyanosis in a compulsive urine drinker.

An 18-year-old gentleman with a habit of compulsive urine drinking was admitted because of repeated vomiting and was noted to be cyanotic. His oxygen saturation was 84% on pulse oximeter but arterial blood gas was normal. He was subsequently confirmed to have methemoglobinemia. He was successfully treated with methylene blue followed by behavioral therapy for his compulsive urine drinking and there was no recurrence of methaemoglobinaemia.