Alkaptonuria

Alkaptonuria is an inherited condition that causes urine to turn black when exposed to air. The three major features of alkaptonuria are the presence of dark urine, ochronosis, a buildup of dark pigment in connective tissues such as cartilage and skin, and arthritis of the spine and larger joints. Ochronosis starts after age 30 and arthritis in early adulthood. Other features of this condition can include heart problems, kidney stones, and prostate stones. Alkaptonuria is caused by mutations in the HGD gene. It is inherited in an autosomal recessive fashion. There is still no cure for this disease. Treatment includes the management of joint pain, physical and occupational therapy, joint replacements and surgery when needed.