A single dose of benzathine penicillin G as an effective treatment for malignant syphilis in an HIV-positive patient: a case report.

Malignant syphilis (MS) is a rare, atypical manifestation of secondary syphilis. Ulcerative lesions should be suspected as MS when found with supporting microscopic morphology, a high syphilis serology titer test, a Jarisch-Herxheimer reaction (JHR), and rapid disease resolution. To date, there is no specific recommendation for treatment for MS. A 24-year-old HIV-positive MSM patient with a CD4 count of 470 cells/µl presented with a chief complaint of necrotic, ulcerative lesions and oyster shell-like surface plaques on his face, trunk, groin, and extremities. The patient also developed various typical presentations of secondary syphilis. Dark-field microscopy revealed spirochetes. Histopathological examination showed spongiotic dermatitis with many neutrophil cells in the dermis, together with endarteritis and fibrin micro-thrombus in the blood vessels. The patient had a high venereal disease research laboratory (VDRL) titer of 1:512. There was rapid disease resolution following a single injection of 2,400,000-unit benzathine penicillin G (BPG); together with anti-retroviral therapy, this was supportive treatment for MS. JHR was not observed in this study and many other reports. This case showed that ulcerative lesions with an oyster shell-like surface presenting in HIV-positive patients along with supporting microscopic morphology, high VDRL titer, and a dramatic improvement after antibiotic treatment is highly suggestive of MS. JHR may no longer be a characteristic of MS. A single dose of 2,400,000-unit BPG is sufficient for MS treatment.