Actinomycosis is a rare infection caused by Actinomyces , an anaerobic gram-positive bacterium from the oral microbiota that can become pathogenic and mimic tumors. This case describes a 52-year-old male patient, smoker, former alcohol user, diagnosed with HIV infection in May 2022. At diagnosis, he had odynophagia since 2021, 14 kg weight loss, oral candidiasis, CD4+ count of 320 cells/µL and HIV viral load of 186,000 copies/mL. Antiretroviral therapy and therapeutic fluconazole were initiated and, at follow-up, the patient had regained weight but persisted with odynophagia. During outpatient visits, he continued to complain of persistent odynophagia. He was admitted to a tertiary infectious diseases service in the Federal District in December 2024 due to weight loss, odynophagia and the appearance of a painful ulcerated lesion on the tongue. On physical examination, he had very poor dentition, a hyperemic plaque on the hard palate and an ulcer with indurated borders on the left lateral tongue. Admission CD4+ count was 1320 cells/µL and HIV viral load was undetectable. CT scans were performed and neck imaging showed an expansive lesion measuring 25 × 26 × 32 mm in the posterior third of the left tongue, with a lateral ulcer extending to the floor of the mouth and bulging of the posterior oropharyngeal wall. The lesion was biopsied and histopathology showed epithelial hyperplasia, regenerative changes associated with chronic inflammatory process, and Actinomyces colonies, with no malignancy. Intravenous crystalline penicillin G was started and, after 6 days, the patient already showed improvement of lesions and pain, no longer requiring analgesics; however, he developed targetoid erythematous plaques (erythema multiforme). Penicillin was suspended and antihistamines were started. Allergy specialists contraindicated desensitization or use of penicillin derivatives. Doxycycline was initiated, but 4 days later the patient left the hospital against medical advice and has not returned for follow-up. Although Actinomyces is a commensal organism in the oral flora, invasive lesions resembling neoplasms are rare. The prognosis is good if the infection is recognized and treated early. This case highlights the unusual nature of this infection, which rarely appears as the first diagnostic hypothesis, and the importance of biopsy to exclude malignancy and guide appropriate management.
Camargos et al. (2026) studied this question.