First case of congenital methemoglobinemia in Nepalese population: a case report.

Introduction and importance: Congenital methemoglobinemia is a rare hereditary disorder that leads to decreased oxygen delivery to the tissues. The severity of symptoms is directly proportional to the methemoglobin levels in the blood. Furthermore, this is the first case of congenital methemoglobinemia reported in the Nepalese population. Case presentation: We herein present a case of a 33-year-old male with congenital methemoglobinemia, the first reported case among the Nepalese population. His peripheral oxygen saturation level did not improve despite increasing the oxygen supplementation, and a saturation gap of more than 5% was present. The dark brown color of the blood was noted on the blood sample. On investigations, the methemoglobin level was 9%. Clinical discussion: Congenital methemoglobinemia can occur due to a deficiency of an enzyme known as cytochrome b5 reductase, which primarily converts methemoglobin to hemoglobin. There are two types of congenital methemoglobinemia, type I and type II which can be distinguished clinically by the presence of neurological impairment and mental retardation, which can be seen in type II congenital methemoglobinemia. Conclusion: Congenital methemoglobinemia is a rare syndrome and has not been previously reported in the Nepalese population. Although there are various diagnostic clues including relevant medical history, saturation gap of more than 5%, dark brown coloration of blood, and investigations such as methemoglobin level, healthcare services like cytochrome b5 reductase enzymatic activity and molecular genetic testing regarding congenital methemoglobinemia is recommended.