Ochronotic arthritis: case reports and review of the literature.

Alkoptunuria is an inherited autosomal recessive metabolic disorder which is caused by the lack of homogentisic acid-oxidase enzyme. It is associated with various systemic abnormalities and related to the deposition of homogentisic acid pigment in connective tissues. These pigmentary changes are termed "ochronosis". We describe two patients with ochronotic arthritis who presented with advanced degenerative changes in the lumbo-sacral spine, knee and hip. The literature, differential diagnosis and management of this rare condition are reviewed in this article.