描述
Alkaptonuria (Homogentisic acid oxidase deficiency) is an autosomal recessive disease caused by a mutation in the HGD gene which codes for homogentisate 1,2-dioxygenase. A mutation in this enzyme results in accumulation of homogentisic acid in urine. Symptoms, which present in adulthood, include arthritis, black or brown urine, and urolithiasis. Treatment includes a low-protein diet with vitamin C.