Alkaptonuria
Summary of Alkaptonuria
Alkaptonuria is a rare autosomal recessive genetic disorder in which the body cannot process the amino acids phenylalanine and tyrosine, leading to accumulation of an intermediate substance called homogentisic acid in the blood and tissues. The accumulating homogentisic acid causes unusually dark urine, damage to cartilage (ochronosis, leading to osteoarthritis) and heart valves as well as precipitating as kidney stones and stones in other organs, including the skin.