[Actinomycosis revealed by ulceration of the palate and gingiva]

Actinomycosis is a chronic and extensive granulomatous, bacterial infection. Revelation by oral ulceration is rare.

A 76-year-old patient with diabetes was treated with dabrafenib for stage IV melanoma. A follow-up visit revealed two ulcerated, infiltrated and hyperalgesic lesions of the palate and gingiva. There were no associated signs. The laboratory findings were normal. The possibility of squamous cell carcinoma occurring with BRAF inhibitors was discussed, despite the rarity of such cases in the literature. Histological examination showed an actinomycotic grain. A scan of the facial mass showed no osteitis. Antimicrobial therapy was initiated with amoxicillin for four months, with a favorable outcome.

Actinomycetes are Gram-positive filamentous saprophytic bacteria of the oral cavity and the gastrointestinal tract. They can become pathogenic under the influence of several factors. Cervicofacial involvement in the form of a peri-mandibular inflammatory nodule with secondary fistulation on the skin or in the mouth is the classic presentation. To our knowledge, no cases of opportunistic infection under BRAF inhibitors have been described. Only two cases of tuberculosis have been reported with sorafenib. The initial presentation led to suspicion of squamous cell carcinoma. In our patient, poor oral hygiene and diabetes were the two key factors considered. Moreover, this is the first case reported under dabrafenib, which does not appear to be a favoring factor. We would stress the importance of mucosal examination in patients treated with BRAF inhibitors.