Congenital methemoglobinemia is caused by gene mutation to decrease the activity or stability of NADH-Cytochrome b5 reductase (b5R),[4] The formation of autosomal recessive genetic disease mainly characterized by methemoglobin (MetHb) reduction disorder.[5,6] There are 2 clinical types: Type I, also known as erythrocyte type, is characterized by decreased stability of b5R, and its clinical manifestations are closely related to the content of MetHb. Here, HBG2 is linked to methemoglobinemia.