Can hydroxychloroquine (HCQ) cause black lines on the nails?

From the Research

Hydroxychloroquine can cause black lines or pigmentation on the nails, known as melanonychia, although this specific side effect is not directly mentioned in the provided studies. The studies provided focus on the efficacy and safety of hydroxychloroquine in treating COVID-19 and its adverse dermatologic effects, but none directly address the specific question of black lines on nails. However, based on the information given in the studies, particularly the one titled "Characterizing the adverse dermatologic effects of hydroxychloroquine: A systematic review" 1, it is known that hydroxychloroquine is associated with various dermatologic adverse effects, including cutaneous hyperpigmentation. Given the context of the question and the known effects of hydroxychloroquine on pigmentation, it is reasonable to consider that it could cause pigmentation changes on the nails as well, similar to its effects on the skin.

• The exact incidence of nail pigmentation due to hydroxychloroquine is not specified in the provided studies.
• The mechanism by which hydroxychloroquine could cause nail pigmentation would likely be similar to its effect on skin pigmentation, involving an affinity for melanin and binding to melanocytes.
• Patients taking hydroxychloroquine for conditions like lupus or rheumatoid arthritis should be aware of potential dermatologic side effects, including pigmentation changes, and discuss these with their healthcare provider during regular monitoring visits. It's also important to consider the broader context of hydroxychloroquine's use and its potential benefits and risks, as discussed in studies like "Update I. A systematic review on the efficacy and safety of chloroquine/hydroxychloroquine for COVID-19" 2 and "Efficacy and safety of hydroxychloroquine as pre-and post-exposure prophylaxis and treatment of COVID-19: A systematic review and meta-analysis of blinded, placebo-controlled, randomized clinical trials" 3, although these studies do not directly address the question of nail pigmentation.