Actinomycosis Causing Recurrent Perianal Fistulae.

Actinomycosis is a rare but easily curable infection that should be considered in the differential diagnosis of perianal fistulizing disease. We present the case of a 26-year-old woman with complex perianal fistulae, including trans-sphincteric and suprasphincteric fistulous tracts and a rectovaginal fistula, requiring multiple abscess drainages, seton placement, and antibiotic courses, with little improvement. After extensive investigation, Actinomyces spp. was identified in anal cytology. The patient underwent a 6-week course of intravenous penicillin followed by oral amoxicillin, with remarkable improvement. This case illustrates the importance of pursuing less common diagnoses in refractory complex perianal disease, such as actinomycosis.