[Alkaptonuria: a rare cause of urine discoloration. Report of a case in a newborn].

Unlabelled: Alcaptonuria is a rare hereditary disease, characterized by an abnormal blackish coloration of the urine and dark pigmentation of the conjunctive tissue which is due to a deficiency in homogentisate 1,2-dioxygenase (HGO), a phenylalanine catabolizing enzyme. An accumulation of homogentisate (HGA) is then formed, and is responsible for the dark coloration which only occurs after the urine has been exposed to air over a period of time. Signs of this disorder therefore frequently remain unnoticed during childhood, because the urine requires a relatively long exposure to air before it changes color.