Phosphodiesterase-5 Inhibitor Use Masking a Necrotizing Syphilitic Infection: A Rare Differential Diagnosis of Priapism.

BACKGROUND: Acute penile enlargement is often presumed to indicate priapism, particularly after Phosphodiesterase-5 inhibitor use. However, alternative diagnoses, including infectious and necrotizing processes, should be considered-especially in patients with a history of unprotected sex-to avoid delayed or inappropriate management. CASE PRESENTATION: A 43-year-old male with a history of intravenous drug use presented with acute penile swelling and leukocytosis (20,500/μL) following unprotected sexual intercourse and tadalafil consumption. Although priapism was suspected, corporal blood gas analysis demonstrated oxygenation and pH levels that excluded ischemic priapism. The patient was admitted to the clinic, and empiric intravenous antibiotics (piperacillin/tazobactam and clindamycin) were initiated. Despite laboratory improvement, penile edema and erythema progressed with early necrotic changes. Postoperative history obtained from a relative revealed prior inadequately treated syphilis, subsequently confirmed by serologic testing. Τhe patient underwent surgical debridement of necrotic tissue surrounding the corporal bodies. He was discharged and referred to a specialized center for syphilis treatment. The patient recovered without further complications and demonstrated preserved erectile function at 1-month follow-up. CONCLUSION: Acute penile enlargement following Phosphodiesterase-5 inhibitor use is not necessarily attributable to priapism and may instead be caused by infectious or necrotizing etiologies. Prompt recognition, initiation of antimicrobial therapy, and timely surgical intervention are critical to preserve penile tissue and erectile function.