Congenital methemoglobinemia is a rare cause of cyanosis. We report a case of a girl, 17 years old with peripheral cyanosis and normal cardio-pulmonary system. She was diagnosed as a case of methemoglobinemia based on findings of polycythemia and HbM band on hemoglobin electrophoresis. We emphasize the importance of this rare entity in the differential diagnosis of cyanosis.

Blue babies lack sufficient hemoglobin, resulting in the bluish discoloration of tissues, a term referred to as cyanosis. There are three major types of cyanosis: central, peripheral and Acrocyanosis and each of them have its specific symptoms, even though the symptoms of central cyanosis overlaps with that of peripheral cyanosis. Cyanosis is diagnosed with auscultation, chest x-ray, electrocar...