Pilonidal sinus of perianal location. Difficult differential diagnosis with perianal fistula.

Pilonidal disease usually arises in the sacrococcygeal area in young men. We present a case of a 39-year-old male with an initial diagnosis of perianal fistula. Despite clinical examination and pelvic magnetic resonance image, only during surgery was revealed that the origin of the fistula was in perianal pilonidal disease. Perianal pilonidal sinus are very rare in the literature. It is often confused with other perianal diseases such as anal fistula. Thus, perianal pilonidal disease should be considered in the differential diagnosis of perianal fistula.