A case of exogenous ochronosis associated with hydroxychloroquine.

Exogenous ochronosis is characterized by hyperpigmented skin lesions that arise in association with local suppression of homogentisic acid oxidase enzyme. Although it generally develops in association with topical application of chemical agents, it can occasionally develop in association with antimalarial drugs. Here we present the case of a patient with rheumatoid arthritis who developed hyperpigmentation on the face and neck regions during hydroxychloroquine treatment. Hydroxychloroquine is being widely used in rheumatology practice, and cutaneous hyperpigmentation may develop as an adverse effect. In the present case, we emphasize the potential underlying mechanisms through which it may cause cutaneous hyperpigmentation and determine the clinical and histopathological findings of exogenous ochronosis.