Clinical Manifestations in 32 Cases of Mpox Infection: A Retrospective Study in a Single Dermatology Clinic in Japan

Mpox, a zoonotic orthopox virus, has re-emerged globally since May 2022. In Tokyo, 168 cases were reported in 2023. About 20% were diagnosed in our department. In this study, we analyzed the clinical and epidemiological characteristics of 32 mpox patients diagnosed in our department in 2023. A retrospective study was conducted using medical records. All cases were confirmed for the diagnosis of mpox by PCR testing using skin samples. The six items were examined: patient background, presumed route of infection, type and site of skin eruption, clinical symptoms other than skin eruption, comorbid infectious diseases, and clinical outcome. All patients were male (median age: 39.5 years) and identified as men who have sex with men (MSM), with 30 reporting recent same-sex sexual activity. Vesicles or small blisters and pustules were the most common eruptions, primarily on the trunk and extremities. Fever occurred in 26 cases, and penile edema was observed in four cases. The HIV-positive rate was approximately 84%, with 53% of patients having a history of both syphilis and hepatitis B. Most cases were observed without treatment with full recovery. When seeing a patient suspected of mpox, it would be recommended to inquire about a history of sexually transmitted infections (STIs), and to test for them even if there is no prior STI history.