Orthopaedic problems in patients affected by alkaptonuria. A case report.

Alkaptonuria is a rare congenital metabolic disorder. A defect of the enzyme homogentisic oxidase results in a block of the metabolic pathway of the amino acids phenylalanine and tyrosine. Deposits of homogentisic acid polymers in connective tissue cause various organ manifestations, including musculoskeletal symptomatology. A 66 year-old woman was twice admitted to our Department because of progressive knee and low back pain. Physical examination and accessory investigations confirmed that her various complaints were caused by underlying alkaptonuria. We use this case and a review of literature to discuss orthopaedic problems in patients with alkaptonuria and describe the cardinal signs and symptoms of this disease, its diagnosis and treatment.