Black cartilage after therapy with levodopa and methyldopa.

A study was undertaken of 14 autopsy cases with pigmented rib cartilage. Twelve of these patients had been treated with levodopa because of Parkinson's disease for at least 6 years, and two had been treated with methyldopa because of essential hypertension for 19 years. Thirty-two percent of the autopsy cases of Parkinson's disease during a recent 70-month period demonstrated pigmented rib cartilage. Only one of them also demonstrated pigmentation of intervertebral disks. No abnormal pigmentation was seen in other sites. The pigment was located in the hyaline matrix of rib cartilage and in necrotic chondrocytes. Levodopa was chromatographically demonstrated within the cartilage of patients with Parkinson's disease, but in both pigmented and unpigmented sites. It is speculated that a pigmented drug metabolite is bound preferentially to the matrix of rib cartilage. Dopa pigmentation only occurs in cartilage and differs in several respects from endogenous and exogenous ochronosis. It appears to be harmless but irreversible.