Atypical genital mpox mimicking a sexually transmitted infection with secondary Staphylococcus aureus infection: A...

Mpox is an Orthopoxvirus infection with evolving clinical presentations, including genital-dominant disease that can resemble common sexually transmitted infections (STIs). Secondary bacterial superinfection is uncommon but may alter lesion morphology and delay diagnosis.

A 64-year-old unhoused heterosexual male presented with a two-week history of painful, malodorous groin ulcers after unprotected intercourse. Lesions began as groin-confined vesicles and later spread to the face and peri-auricular area. Because of ulceration, purulence, and sexual exposure, initial evaluation focused on more common sexually transmitted infections, all of which tested negative. Dermatology was consulted when the eruption showed umbilicated vesiculopustules at uniform developmental stages. Punch biopsies demonstrated neutrophilic pustules consistent with Orthopoxvirus infection, and PCR confirmed mpox. During hospitalization, several lesions became purulent with foul odor; culture grew methicillin-sensitive Staphylococcus aureus. Linezolid therapy produced rapid improvement.

This case demonstrates genital-dominant mpox in a heterosexual male, a less commonly reported demographic, and highlights how lesion morphology may mimic bacterial or viral STIs. Bacterial superinfection can obscure classic diagnostic features, contribute to malodor and purulence, and delay recognition. PCR remains essential for confirmation, particularly when presentation overlaps with other genital ulcer etiologies.

Clinicians should include mpox in the differential diagnosis of genital ulcer disease regardless of sexual orientation and maintain vigilance for bacterial superinfection in non-healing or purulent lesions. Early PCR testing and culture-directed therapy are essential for accurate diagnosis and optimal management.