A complex presentation of complicated secondary syphilis with ulcerated lesion progression.

Secondary syphilis is commonly associated with well-known cutaneous and mucosal manifestations, including maculopapular rashes and condylomata lata. However, clinical presentation can vary significantly, often resembling other dermatological or infectious conditions, which can lead to diagnostic delays and challenges, particularly in immunocompetent individuals. We report the case of a 26-year-old heterosexual Asian man working as a baggage handler at a busy international airport, who presented with a rapidly progressive, painful rash. Initially treated with flucloxacillin, his condition worsened, spreading to his face, trunk, and mucous membranes, accompanied by fever, tachycardia, and difficulty swallowing. Physical examination revealed widespread umbilicated vesicles, haemorrhagic blisters on his right lower leg, and ulcers in the oral cavity. Despite negative results for common viral infections (HSV, VZV, HIV) and autoimmune disorders, serological testing for syphilis revealed a positive rapid plasma regain test, confirmed by a positive treponemal antibody EIA test and subsequent clinical improvement with appropriate antibiotic therapy. Following the diagnosis of secondary syphilis, the patient was treated with benzathine penicillin and supportive care. He experienced a mild Jarisch-Herxheimer reaction, which resolved with monitoring. A subsequent infection of a fungating lesion (bacteria superimposition) on the right shin was managed with amoxicillin/clavulanic acid. By the patient's follow-up visit, the skin lesions had markedly improved, and he was discharged with ongoing care and penicillin treatment. This case highlights the importance of considering syphilis in the differential diagnosis of atypical cutaneous and mucosal lesions, especially when presenting with systemic symptoms. The diagnosis of secondary syphilis can be challenging due to its diverse clinical manifestations, which may mimic other infectious or autoimmune conditions. A careful diagnostic approach, including serological and polymerase chain reaction testing, is essential for accurate diagnosis and effective treatment. This case also emphasizes the need for timely public health intervention and education in high-risk populations.