Severe Phototoxic Vesiculobullous Eruption Following Sequential Exposure to Terbinafine, Ciprofloxacin, and Trimethoprim-Sulfamethoxazole.

Phototoxic drug eruptions are well-recognized adverse reactions to several classes of medications, including fluoroquinolones, sulfonamides, and antifungals. However, sequential photosensitization following exposure to multiple agents is rarely described. We present the case of a 44-year-old Hispanic male commercial driver who developed a severe, vesiculobullous, photo-distributed rash following sequential exposure to terbinafine, ciprofloxacin, and trimethoprim-sulfamethoxazole (Bactrim). The patient initially presented with ringworm of the lower extremity and was started on topical and oral terbinafine. When the rash worsened approximately one week later, he was sequentially prescribed ciprofloxacin and then Bactrim for suspected cellulitis. Each new medication was associated with progressive worsening of the rash, which was confined to sun-exposed areas (distal arms, distal legs, neck) and characterized by erythema, pruritus, pain, clear fluid-filled vesicles, and superficial skin peeling. There was no mucosal involvement, no Nikolsky sign, and no systemic symptoms. Laboratory evaluation revealed elevated C-reactive protein (2.7 mg/dL) with normal complete blood count, comprehensive metabolic panel, erythrocyte sedimentation rate, and negative autoimmune serologies (antinuclear antibody, anti-SSA, anti-SSB). Infectious workup, including HIV, syphilis, hepatitis panel, and blood cultures, was negative. An infectious disease consultant ruled out onychomycosis and cellulitis. All suspected offending medications were discontinued on admission. The patient was treated with intravenous methylprednisolone (40 mg every eight hours for three days), topical clobetasol, and supportive care. By hospital day three, the erythema had resolved completely, the vesicles had substantially decreased, and the pain had resolved. The patient was discharged home on a prednisone taper. This case highlights the importance of recognizing phototoxic drug eruptions in patients presenting with photo-distributed vesiculobullous rashes, particularly when multiple photosensitizing medications have been prescribed sequentially. A systematic approach to excluding infectious, autoimmune, and other drug-induced conditions is essential for diagnosis when a biopsy is not available.