Novel compound heterogeneous mutations in CYB5R3 gene leading to methemoglobinemia (type I) in a Chinese boy

Recessive congenital methemoglobinemia (RCM) caused by CYB5R3 deficiency due to the mutations in the reduced nicotinamide adenine dinucleotide (NADH) cytochrome b5 reductase (CYB5R) gene is an autosomal recessive inherited disease. Clinically, it can be divided into two types, namely red blood cell affected type (RCM I) and systemically affected type (RCM II).