Methemoglobinemia, also known as "met-H", is a usually genetic blood disorder characterized by the presence of a higher than normal level of methemoglobin in the blood.
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 parent has this gene offspring will have normal-hued skin, but if both parents carry the gene there is a chance the offspring will have blue-hued skin.
Acquired methemoglobinemia can be caused by the use of nitrate-containing drugs, such as nitroglycerin.
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