Unrecognized ochronosis--a case report.

Alkaptonuria is a rare metabolic disorder characterized by a deficiency of the homogentisic acid oxidase enzyme. The result is accumulation of homogentisic acid in collagenous structures throughout the body, especially in fibrous and cartilaginous tissue. This leads to gradual development of a phenomenon known as ochronosis. Characteristic features of ochronosis are urine darkening, progressive scleral pigmentation, subcutaneous cartilage pigmentation (for example, ear cartilage and nails) and degenerative ochronotic arthropathy resembling osteoarthritis. In addition, cardiovascular and genitourinary systems are also affected. Alkaptonuric ochronosis is particularly interesting because it can be detected based only on clinical signs and medical history. Herein we present a patient with typical signs and symptoms such as darkening of urine, pigmented sclerae, nails and ear cartilage, manifesting arthritis in his fifth decade. Additional clinical examination indicated alkaptonuria, which was unrecognized in childhood.