Longitudinal melanonychia and skin hyperpigmentation associated with hydroxychloroquine therapy

Antimalarials, including hydroxychloroquine (HCQ), may cause hyperpigmentation of the skin, mucous membrane, joints, and cartilage.1-3 Longitudinal melanonychia, a linear brown-black nail plate band, is rarely reported with HCQ treatment, and histologic confirmation has not been previously published. HCQ is widely used for the treatment of various rheumatic and dermatologic diseases, including systemic lupus erythematosus, cutaneous lupus, and rheumatoid arthritis. It inhibits the replication of SARS-CoV-2 in vitro4 and has been used to treat COVID-19.