a genetic disease in which the urine turns black when exposed to air, due to homogentistic acid in the urine
a rare recessive metabolic anomaly marked by ochronosis and the presence of alkapton in the urine
Due to deficiency of homogentisic acid oxidase with features of ochronosis - pigmentation of articular cartilage, early osteoarthritis and calcification of intervertebral discs Urine turns dark on standing