Congenital methaemoglobinaemia

**Definition:** A disease caused by determinants in the antenatal period leading to lack of the enzyme cytochrome b5 reductase. This disease is characterised by elevated levels of methemoglobin within the blood leading to haemoglobin ineffectively releasing oxygen to body tissues. This disease may present with shortness of breath, cyanosis, headache, fatigue, exercise intolerance, dizziness and loss of consciousness. Confirmation is by identification of mutation by genetic testing.