Pilonidal disease is caused by insertion of hairs into the skin of the natal cleft, at the sacrococcygeal region. This causes a chronic inflammatory response, with formation of a discharging sinus. Infection of the region may precipitate abscess formation.
Pilonidal disease typically occurs in male patients age 15-40 and is more common in the presence of thick stiff body hair. Patients typically present with offensive discharge from the natal cleft and discomfort, especially when seated.
On physical examination sinus tracts may be visible around the natal cleft.
If superinfection occurs, there may be abscess formation which results in a tender fluctuant swelling and low-grade fever.