A RARE CAUSE OF NEONATAL CYANOSIS - CONGENITAL METHEMOGLOBINEMIA — A CASE REPORT

Abstract

Cyanosis can occur at any age but it is a great challenge when it is in the newborn. Multiple causes have been established, and it usually is an ominous sign, especially when it occurs with neonatal sepsis or cyanotic congenital heart disease. Cyanosis caused by abnormal forms of hemoglobin can be life threatening, and early recognition is mandatory to prevent unnecessary investigations and delay in management. Abnormal hemoglobin newborn screening is a useful tool for the diagnosis. Acquired methemoglobinemia caused by environmental oxidizing agents, is common, but congenital deficiency of the innate reducing enzyme is so rare that only a few cases are documented in the medical literature around the world. Here I am presenting a case of a neonate with cyanosis as a result of congenital deficiency of cytochrome b5 reductase enzyme. This neonate was found to have cyanosis and appeared blue at newborn follow-up visit. Sepsis, congenital heart disease, prenatal administration, and ingestion of oxidant dyes were excluded as causes of the cyanosis by history, examination and appropriate tests. Chocolate discoloration of arterial blood provided a clue to the diagnosis. A normal newborn screen and hemoglobin electrophoresis made the diagnosis of hemoglobin M unlikely as the cause of the methemoglobinemia (Hb A 58.9%, A2 1.9%, and F 39.2%). Red blood cell enzyme activity and DNA analysis revealed a homozygous form of the cytochrome b5 reductase enzyme deficiency. She responded very well to daily methylene blue and ascorbic acid administration, and she has normal growth and developmental parameters, although she shows an exaggerated increase in her methemoglobin level.