Causes
Coccygeal fistulae (Pilonidal Fistula) are cysts which form under the skin in the gluteal folds. The cause of the formation of these cysts in many cases is a broken hair which due to the rubbing of the skin, forms or grows. These foreign bodies are encapsulated by the formation of a cyst and can be severely infected by the bacteria of an ingrown hair. An abscess can result.