Hydroxychloroquine: Dermatologic Uses and Retinal Screening

Overview / Definition Hydroxychloroquine (HCQ) is a synthetic derivative of chloroquine, primarily used as an antimalarial agent. In dermatology, it is predominantly employed for the management of various autoimmune conditions, particularly systemic lupus erythematosus (SLE) and dermatomyositis. Hydroxychloroquine exhibits anti-inflammatory and immunomodulatory effects, making it effective in treating skin manifestations associated with these diseases. Epidemiology Hydroxychloroquine is commonly prescribed, especially among women aged 15 to 45 years, given the higher prevalence of autoimmune diseases in this demographic. The incidence of SLE is approximately 1.5 to 7.5 cases per 100,000 individuals per year, and the use of HCQ has significantly improved the management of this disease. Pathophysiology / Mechanism The exact mechanism of action of hydroxychloroquine in dermatological conditions is not fully understood. However, it is thought to involve: Inhibition of lysosomal function: HCQ accumulates in lysosomes, altering pH and disrupting antigen processing. Reduction of cytokine production: It decreases the production of pro-inflammatory cytokines such as TNF-α and IL-1. Inhibition of TLR signaling: Hydroxychloroquine inhibits Toll-like receptor (TLR) signaling, which is pivotal in the autoimmune response. Clinical Presentation Hydroxychloroquine is primarily indicated for: Systemic Lupus Erythematosus (SLE): Patients may present with a characteristic butterfly rash, photosensitivity, and other systemic manifestations. Dermatomyositis: Presents with heliotrope rash, Gottron's papules, and muscle weakness. Chronic Cutaneous Lupus Erythematosus: Characterized by discoid lesions on sun-exposed areas. Other dermatological conditions where hydroxychloroquine may be beneficial include psoriasis, lupus panniculitis, and bullous pemphigoid. Diagnosis / Workup Diagnosis of conditions treated with hydroxychloroquine involves a thorough clinical evaluation along with laborat