Ochronotic arthropathy as a paradigm of metabolically induced degenerative joint disease. A case-based review.

Alkaptonuria is a rare, hereditary metabolic disorder in which a deficiency in the homogentisate 1,2-dioxygenase enzyme results in an accumulation of homogentisic acid. Deposition of excess homogentisic acid in different intra- and extra-articular structures with high content of connective tissue causes brownish-black pigmentation and weakening, ultimately resulting in tissue degeneration and finally osteoarthritis. Ochronotic arthropathy is considered a rapidly progressive, disabling condition in which weight-bearing joints and the thoracolumbar spine are predominantly affected. Patients often require multiple joint replacements, such as in the case of the patient presented here. At present, there is no definitive cure for ochronosis, and management is predominantly symptomatic.