Recent infection with monkeypox virus can initially present with very few pronounced clinical symptoms and lacking signs of infection, and only few skin vesicles may be visible.
Stefan Schlabe and coauthors present the case of a 51-year-old HIV-positive patient, whose ulcer at the corner of his mouth occurred as the first sign of infection with monkeypox virus (Schlabe S, Isselstein J, Boesecke C: Ulcer at corner of mouth as first sign of infection with monkeypox virus.

The patient presented to his general practitioner with a vesicle at the left corner of the mouth that had appeared the day before. He had no clinical signs of infection; his HIV infection had been well controlled for years, both virologically and immunologically, with antiretroviral therapy. Initially, the patient's ulcer was treated with a topical combination ointment. Within a few days, he developed a painful ulcer at the left corner of his mouth and went back to his general practitioner.
A swab was taken from the ulcer. Testing by polymerase chain reaction (PCR) confirmed monkeypox virus. Subsequently an increase in monkeypox vesicles was noted on the skin, but also on the palate. With growing swelling of the base of the tongue and muffled speech, it was decided to admit the patient to hospital for antiviral treatment with tecovirimat.
Reference:
Schlabe S, Isselstein J, Boesecke C: Ulcer at corner of mouth as first sign of infection with monkeypox virus. Dtsch Arztebl Int 2022; 119: 511. DOI: 10.3238/arztebl.m2022.0274