The congenital type is believed to be a deficiency of the enzyme NADH-cytochrome b5 reductase (absence of reductive pathways). The reduced ability to bind oxygen leads to poor oxygenation of body tissues, contributing to cyanosis and hypoxia in affected infants. Other signs and symptoms include neurological irregularities (hyperkinetic movements, seizures, or quadriparesis), microcephaly, mental deficiency, poor feeding, and failure to thrive. Can be life-threatening or lead to greatly reduced functionality and shortened life expectancy.
Management includes discontinuance of causative drug or chemical compound. Absent a history of hemolysis, intravenous methylene blue and ascorbic acid may be used. In severe cases, management in intensive care, close observation and support of breathing and circulation function, hyperbaric oxygen, red blood cell exchange, and intubation are options.
D74.9 – Methemoglobinemia, unspecified
38959009 – Methemoglobinemia