Hydroxychloroquine is associated with myriad adverse dermatologic effects, most of which are poorly characterized by the literature, with unknown frequencies and risk factors.

To conduct a systematic review of the adverse dermatologic effects and predisposing factors of hydroxychloroquine toxicity.

The review included 94 articles comprising 689 dermatologic adverse effects. A total of 21 unique dermatologic reactions were reported, most commonly drug eruption or rash (358 cases), cutaneous hyperpigmentation (116), pruritus (62), acute generalized exanthematous pustulosis (27), Stevens-Johnson syndrome or toxic epidermal necrolysis (26), hair loss (12), and stomatitis (11). Almost all underlying conditions were rheumatologic or autoimmune in nature, composed primarily of lupus erythematous (72% of all cases) and rheumatoid arthritis (14%). The range of reported mean cumulative dosages was wide, with some adverse reactions found after as little as 3 g or as much as 2500 g.

Dermatologic adverse events and primary diagnoses related to the use of hydroxychloroquine may be under-reported as only case reports and clinical trials that reported at least 1 dermatologic adverse effect were included.

Although hydroxychloroquine is generally well tolerated, dermatologic adverse effects involving the skin, hair, or nails are a frequent and significant complication. Most of these reactions occurred after treatment of autoimmune conditions, often manifesting on the skin after a wide range of cumulative dosages.