Drug-Induced Phototoxicity in Vitiligo: The Role of Hydrochlorothiazide in Photosensitivity Dermatitis.

Photosensitivity dermatitis is a multifactorial dermatologic condition characterized by an exaggerated cutaneous response to ultraviolet (UV) radiation, often exacerbated by exogenous agents, particularly photosensitizing medications. The pathophysiology involves direct phototoxic or immune-mediated photoallergic mechanisms, leading to inflammatory skin reactions upon UV exposure. In individuals with vitiligo, the absence of melanocytes in depigmented areas significantly diminishes photoprotective mechanisms, rendering these regions highly susceptible to UV-induced damage. Consequently, vitiliginous skin is inherently more vulnerable to photo-induced inflammation and cutaneous injury. We report a 54-year-old man with generalized vitiligo who developed erythematous papules confined to sun-exposed depigmented skin. The clinical course suggested a medication-induced phototoxic reaction, likely potentiated by the patient's underlying lack of cutaneous melanin. This case highlights the need to recognize drug-induced photosensitivity in vitiligo and understand how UV vulnerability and photosensitizing medications interact.