Human mpox presenting with penile edema and ulcer: A case report.

Human mpox, which has spread worldwide since May 2022, is characterized by symptoms involving the genital area; however, its treatment methods and clinical course are not completely understood. Furthermore, penile swelling in human mpox can be difficult to differentiate from cellulitis and antibiotic use has been reported in such cases. Herein, we report a case of human mpox in Japan with prominent penile swelling and persistent penile ulcers that improved without specific treatment. The patient was a Japanese man in his 20s with a history of having sexual intercourse with men frequently. He visited Tokyo Metropolitan Toshima Hospital because of a fever and rash in the genital area. Physical examination revealed vesicles on the limbs, penile pigmentation, and significant penile swelling and redness. There were no signs of cellulitis and symptomatic treatment was initiated with outpatient follow-up. After 7 days, an improving trend in penile swelling, redness, and pain was observed. However, a partially black skin ulcer with exudate was observed at the left coronal sulcus of the penis. Therefore, the symptomatic treatment was continued. On illness day 28, the penile swelling completely improved; however, the penile ulcer and pain persisted, and the exudate was observed again. By illness day 63, the pain in his anogenital area had disappeared, and the penile skin ulcer had healed. The following observations were noted in this case: (i) human mpox can improve without specific treatment such as tecovirimat administration and (ii) skin lesions in the genital area may change over time.