[Severe osteoarthritic manifestations of ochronosis].

The congenital form of ochronosis is a result of the rare autosomal recessive inherited metabolic disease alkaptonuria. The disruption of tyrosine metabolism based on a genetic defect in the enzyme homogentisate dioxygenase results in accumulation of homogentisic acid (HA) which is excreted in the urine and leads to a dark discoloration after a certain incubation time at room temperature. Furthermore, HA polymerizes forming a pigment that is deposited in connective tissues such as tendons, cartilage, bones, intervertebral discs, sclerae, ossicles, cardiac valves and coronary arteries and leads to dark brown discoloration and degeneration. The case of a 74-year-old female patient with ochronosis and classical manifestations is described and in addition a current overview of this rare disease is provided.