[Non-cardiac cyanosis: methemoglobinemia in infants].

Methemoglobinemia is a rare but easily diagnosed disease which may resemble cyanotic congenital heart disease. Toxic agents, mainly nitrate absorption, are often responsible and may reveal an underlying permanent or transient enzyme deficiency. Methemoglobinemia is of poor prognosis if secondary to hemoglobin disorders or congenital enzyme deficiency. Methylene blue is a good aid to diagnosis and a treatment of choice.