Hereditary Methemoglobinemia Due to Cytochrome b5 Reductase Deficiency

We report a boy with chronic central cyanosis since birth. He was otherwise asymptomatic with chocolate brown color of blood. Methemoglobinemia was suspected after exclusion of the cardiac and pulmonary diseases. Hereditary methemoglobinemia was considered by his clinical course. The simple bedside procedure could be performed to determine methemoglobinemia by vigorous shaking his blood with oxygen and observing the same chocolate brown in color. Spectrophotometer could be used to confirm this condition by measuring the change in optical density at 630 nm. Cytochrome b5 reductase deficiency was diagnosed by using a simple spot screening test of the enzymatic activity. The patient was treated by the administration of ascorbic acid with reducing of cyanosis and methemoglobin level. Although hereditary enzymopenic methemoglobinemia is a rare autosomal recessive disorder. This disease should be considered in the patient with chronic asymptomatic cyanosis even no history of consanguinity.