The safety profile of hydroxychloroquine: major cutaneous and extracutaneous adverse events

Hydroxychloroquine is an established therapy for several rheumatological disorders, and very recently it has been proposed as a possible treatment for the new coronavirus disease 2019 even if recent randomised trials did not prove any benefit. Notably, hydroxychloroquine has been associated with a heterogeneous range of cutaneous and extra-cutaneous adverse events. We carried out a narrative review of the literature up to November 1st, 2020, related to the safety of hydroxychloroquine. In particular, cutaneous and extra-cutaneous adverse events associated with hydroxychloroquine were reviewed. The following databases were consulted: PubMed, Embase, Google Scholar and ResearchGate. The research of articles was conducted by using the following search terms: ''hydroxychloroquine," ''adverse event/effect,'' "cutaneous", "skin", "cardiotoxicity", "retinopathy", gastrointestinal and neurological toxicity". The main indication for which hydroxychloroquine was used in the reports was an immune mediated disorder. Adverse events were described mostly in females over 50 years of age. The most common cutaneous adverse effect was maculopapular and erythematous rash occurring within 4 weeks of initiating hydroxychloroquine and disappearing within few weeks of discontinuation. Gastrointestinal symptoms and headache were the most frequent extracutaneous manifestations. Rarer cutaneous manifestations include hyperpigmentation, psoriasiform dermatitis, photodermatitis, stomatitis, melanonychia and hair loss. More severe conditions were acute generalised exanthematous pustulosis, drug rash with eosinophilia and systemic symptoms, Stevens-Johnson syndrome/toxic epidermal necrolysis, and among extra-cutaneous adverse events cardiotoxicity and retinopathy. Since hydroxychloroquine is widely prescribed in rheumatology, it is important for rheumatologists to be familiar with its safety profile.