Methemoglobinemia as an uncommon cause of cyanosis.

Cyanosis is usually caused by decreased arterial oxygen saturation due to pulmonary or cardiac diseases. Methemoglobinemia is a rare cause, sometimes with lethal outcome. Two patients are described, both with an unremarkable cardiopulmonary history, presented with severe cyanosis due to aniline-induced methemoglobinemia that developed at work. The symptoms and the treatment of methemoglobinemia are discussed.