Follmann balanitis as an atypical form of primary cutaneous syphilis

Abstract

Introduction: Follmann balanitis is a rare and atypical manifestation of primary syphilis, characterized by erosive, inflammatory lesions of the glans penis that can mimic other infectious or inflammatory causes of balanitis. Due to its unusual clinical appearance, misdiagnosis or delayed diagnosis is common, emphasizing the importance of maintaining a high index of suspicion in sexually active individuals. Case Report: A 33-year-old male presented with a painful erythematous plaque with erosions over the glans penis, persisting for 20 days. The lesion appeared eight days following unprotected oral and vaginal heterosexual intercourse. There was no history of new medication use, drug intake, systemic symptoms, or previous similar episodes. Physical examination revealed a large, well-demarcated erosive erythematous plaque involving the glans and extending to the foreskin, with no associated regional lymphadenopathy or other cutaneous lesions. Based on the sexual history, a comprehensive screening for sexually transmitted infections was performed. Swabs from the erosive lesions were negative for bacterial and fungal cultures, and herpes simplex virus polymerase chain reaction (HSV PCR) results were also negative. Serological testing demonstrated a positive Treponema pallidum hemagglutination assay (TPHA 1/320) and a positive rapid plasma reagin (RPR 1/32), confirming the diagnosis of primary syphilis presenting as Follmann balanitis. The patient was treated with a single intramuscular dose of 2.4 million international units of benzathine penicillin G, resulting in significant clinical improvement within two weeks. Rapid plasma reagin (RPR) titer dropped to fourfolds within three months. Conclusion: This case underscores the importance of considering syphilis in the differential diagnosis of atypical erosive balanitis. Prompt serological testing and appropriate antibiotic therapy are essential for achieving rapid resolution and preventing disease progression or transmission.