Due to an enzyme deficiency, the blood of met-H victims has reduced oxygen-carrying capacity. Instead of being red in colour, the arterial blood of met-H victims is brown. This results in the skin of Caucasian sufferers gaining a bluish cast. Hereditary met-H is caused by a recessive gene. If only one of parent has this gene, the offspring will have normal hued skin, but if they both have the disorder, there a good chance the offspring will have blue-hued skin.
The disease is readily treatable by replacing the missing enzyme in the blood of the victim.