hereditary methemoglobinemia

Epidemiology

very uncommon

Pathology

• 3 forms
• type 1 (HM1) in which the enzyme is only deficient in erythrocytes with a mild cyanosis
• type 2 (HM2), in which the enzyme is completely deficient
• type 3 (HM3) where deficiency is seen in all blood cells

Genetics

• associated with defects in CYB5R3

Clinical manifestations

• minimal to moderate cyanosis
• type 2 is a severe form accompanied with mental retardation & neurological impairment

Laboratory

• increased venous blood methemoglobins of 10-20% of total hemoglobin

More general terms

• methemoglobinemia
• genetic disease of the blood/bone marrow

Database

• OMIM: https://mirror.omim.org/entry/250800