Alkaptonuria
Alternate Names : Alcaptonuria, Homogentisic Acid Oxidase Deficiency, Ochronosis
Definition Alkaptonuria is a rare inherited disorder of metabolism characterized by urine which turns black when exposed to air. Another characteristic is the development of arthritis in adulthood.
Overview, Causes, & Risk Factors
Alkaptonuria is an autosomal recessive inherited disorder. In affected individuals, an amino acid known as tyrosine is not properly metabolized, due to a defect in an enzyme called homogentisic acid oxidase.
Because of the defect, homogentisic acid is excreted in the urine and turns a brown color upon exposure to air. This is the result of a dark pigment with an ochre color (earthy red or yellow), which led to the name ochronosis. The bones and cartilage of the body can be brown colored.
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