Alterations of Phenylalanine Metabolism: Alkaptonuria

    Alkaptonuria is a metabolic disease characterized by the accumulation of Homogentistic Acid (formerly known as Alkapton) in the urine. Exposure of Homogentisic Acid to light results in its darkening, thus producing the characteristic "black diaper" disease. In adults, homogentisic acid may be deposited in cartilage of the ears and nose, resulting in darkening of these areas. The medical effects of alkaptonuira are otherwise not severe.