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Pilonidal sinus disease is an inflammatory condition involving the hair follicles that can occur anywhere along the crease between the buttocks, which runs from the bone at the bottom of the spine (sacrum) to the anus. The disease is benign and has no association with cancer.

Pilonidal disease may appear as:

• A small pit or pore in the skin that contains dark spots or hair
• A pilonidal sinus, in which a tract grows under the skin or deeper from the hair follicle
• A pilonidal cyst, in which a pocket of fluid forms underneath the pit or sinus
• A pilonidal abscess, in which the pilonidal cyst becomes infected and pus collects in the adjacent fat tissue