Late syphilis presenting with extensive granulomatous cutaneous and pulmonary involvement

Introduction Syphilis is a protean infection capable of mimicking various dermatological and systemic diseases, often complicating diagnosis in its later stages. Case presentation A 26-year-old HIV-negative man with a history of inadequately monitored syphilis presented with headache, cough, and widespread erythematous plaques with central atrophy. Investigations revealed an RPR titer of 1:128 and positive CSF treponemal serology. Chest CT demonstrated peripheral nodular lung consolidations, and ophthalmologic exam showed signs of prior uveitis. A skin biopsy confirmed late-stage syphilis, revealing extensive dermal tuberculoid granulomas and gummatous necrosis. Following a 14-day course of intravenous penicillin G, the pulmonary lesions completely resolved, cutaneous lesions markedly improved, and the RPR titer appropriately declined at the six-month follow-up. Conclusion This case illustrates a rare presentation of late syphilis with concurrent pulmonary involvement and widespread granulomatous skin lesions, emphasizing the need for clinicians to maintain a high index of suspicion for atypical manifestations of Treponema pallidum.