Autosomal recessive type 2 hereditary methemoglobinemia, also referred to as recessive congenital methemoglobinemia type 2 (RHM type 2/RCM type 2), is a rare red cell disorder characterized by severe encephalopathy with generalized dystonia and mild cyanosis. The disease is Orphanet_139380 (Recessive hereditary methemoglobinemia type 2). Also known as: NADH-cytochrome b5reductase deficiency type 2, NADH-diaphorase deficiency type 2, Recessive congenital methemoglobinemia type 2.