Alkaptonuria presenting as lumbar disc prolapse: case report and review of literature.

Alkaptonuria is a rare genetic disorder caused by deficiency of the enzyme homogentisic acid oxidase, resulting in accumulation of homogentisic acid in various body tissue; it produces a multisystemic disorder with a characteristic bluish-black discolouration of the skin and cartilage, termed ochranosis. Ochranosis primarily involves the large joints of the body including the spine. Spinal involvement produces loss of flexibility and ankylosis of the thoracic and lumbar segments. The clinical presentation with spondylosis and canal stenosis is common after the third and fourth decades, but intervertebral disc prolapse is unusual in ochranosis.