causes condition has contributing genetic variation Hemoglobin M Disease Genotype Hemoglobin Genotype M None Haemoglobin Genotype M Hemoglobin M Genotype Request inclusion into relevant ontology The presence of an amino acid substitution in either an alpha-, beta-, or gamma-globin chain such that its proximity to the heme iron in the hemoglobin molecule results in facilitated oxidation of the hemoglobin to yield excess methemoglobin. This can occur in either one or both alleles of the effected gene. SCDO (Jade Hotchkiss) CYB5R3 Mutation