Methemoglobinemia is a ocndition in which the hemoglobin's oxygen carrying capacity is reduced, leading to hypoxia and cyanosis. Autosomal recesisve methemoglobinemia is of two types. Type I is a relatively benign condition, characterized by cyanosis. Type II is a more severe form, characetrized by cyanosis in association with severe intellectual disability and neurological impairment.
Mutations in the CYB5R3 genes are causal for both Types of autosomal recessive Methemoglobinemia.