Overlap of psoriasiform and primary syphilis: an atypical manifestation of secondary syphilis (a case report)

Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum (T. pallidum) with an increasing incidence in recent years. Secondary syphilis is called 'the great imitator' due to its various clinical presentations. Psoriasiform syphilis is an atypical presentation of secondary syphilis. The coinfection of syphilis with HIV has been linked to more severe clinical presentations increased risk of neurosyphilis, decreased CD4+ count, and an interesting phenomenon of overlapping primary and secondary syphilis. A 35-year-old male presented with generalized thick, scaly erythematous plaques, including the soles of the palms and feet, diffuse alopecia on the scalp and eyebrows, and multiple painless ulcers on the penis. The venereal disease research laboratory and Treponema pallidum hemagglutination assay examination showed positive results and the patient was treated with an intramuscular injection of 2.4 million units of Benzathine penicillin G. At the seventh-day follow-up, the patient showed significant clinical improvement marked by plaque thinning and reduced erythema. This case emphasizes that secondary syphilis may present with varied clinical presentations which can be further affected with HIV coinfection. Detailed history taking, physical examination, and a high level of suspicion are crucial in recognizing and establishing the right diagnosis.