Secondary Syphilis Presents as Palmoplantar Hyperpigmented Maculopapules: A Case Report

Syphilis is a worldwide chronic systemic sexually transmitted infection caused by the spirochete bacterium Treponema pallidum. Here, we report a 28-year-old homosexual male who presented to the dermatology clinic with a six-month history of asymptomatic persistent skin lesions. A review of systems revealed unintentional weight loss of about 40 kg within one year. Skin examination revealed multiple scaly and non-scaly hyperpigmented macules and patches on the palms and soles. Hair, nail, and mucus membrane examinations were normal. There was no lymphadenopathy. A skin biopsy revealed psoriasiform acanthosis, lichenoid infiltrates with moderately dense mononuclear lymphohistiocytic cells, few plasma cells, and eosinophils. Laboratory investigations revealed positive rapid plasma reagin (RPR) with a titer of 1:128. Treponema pallidum hemagglutination test (TPHA) was positive. The HIV test by western blot was positive. Based on the above clinicopathological and laboratory findings, a diagnosis of secondary syphilis was made in this patient, who also tested positive for HIV. He was given a single dose of penicillin G benzathine (2.4 units) intramuscularly. He was also started on Dolutegravir 50 mg tablet once daily and Tenofovir alafenamide fumarate + Emtricitabine tablet once daily. Three months after penicillin G benzathine treatment, the RPR test turned negative, and the skin lesions disappeared.