Monkeypox virus infection mimicking primary syphilis

In our case series of monkeypox (MPX) virus infected patients, one had a single genital ulcer as the only cutaneous manifestation of the infection. Physical examination revealed a single, rounded ulcer of the shaft penis characterized by pinkish raised, infiltrated borders and a crusty yellowish bottom associated with bilateral inguinal lymphadenopathies. Serology for Treponema pallidum infection and a complete screening for sexually transmitted infections (STIs) resulted negative except for the detection of Staphylococcus aureus at the cultural examination and MPX DNA at the ulcer bottom. The patient's general conditions were good therefore he remained isolated at home for 3 weeks after the diagnosis. At one month follow up, he presented only a depressed pinkish skin scars on the site of the previous ulcer. The clinical presentation of this patient could easily be misdiagnosed with other sexually transmitted infections (STIs), especially with primary syphilis. MPX infection should be considered in the differential diagnosis of STIs, also in patients with weak and localized manifestations.