A 32-year-old man with well-controlled HIV infection presented with a chief symptom of severe rectal pain that worsened over the previous week. He had receptive anal intercourse 13 days before presentation. He described a burning or tearing sensation inside his rectum and an associated clear discharge.

One week earlier, he had diarrhea for two days and developed a rash that started on his legs and spread to his arms and back. He also had a large lesion on his forehead. Two days previously, he presented to another clinic with subjective fevers and night sweats and was treated with doxycycline and ceftriaxone. He did not have chest pain, shortness of breath, or abdominal pain. He did not have recent travel or known infectious contacts.

Physical examination revealed diffuse, salmon-colored macules and papules on his left arm, papules and vesicles on his back, and an umbilicated lesion on his forehead (Figure 1 and Figure 2).

Question

Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?

• A. Gonorrhea.

• B. Herpessimplex.

• C. Mpox (monkeypox).

• D. Syphilis.

• E. Ulcerativecolitis.