Pilonidal Cysts: What Are the Risk Factors?

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: Jay W. Marks, MD

Pilonidal cysts arise at the base of the tailbone (coccyx) of the lower back, just above the natal cleft (the cleavage between the buttocks). Doctors sometimes use the term pilonidal disease to refer to the range of problems that can affect this area. In simple cases, a small, solitary cyst-like area containing fluid is present without evidence of infection. In other cases, the areas may become infected and filled with pus, creating a so-called pilonidal abscess. When the condition is particularly severe, the infection can spread, creating multiple abscesses and sinus tracts (abnormal paths of tissue destruction). The term "cyst," which is generally used in this case, is actually a misnomer since true cysts have a characteristic cellular lining that is lacking in the vast majority of cases of pilonidal disease.

Small pilonidal cysts may not cause any symptoms if they do not become infected. Symptoms and signs of a pilonidal cyst or abscess include swelling (a localized "bump" may be noticed), pain, and redness at the base of the spine. In the case of a pilonidal abscess, the pain and redness usually are greater, and fever may be present.

Most experts believe that the cysts arise due to trauma to the area that results in ingrown hairs. Pilonidal cysts often contain hair when excised, but hair follicles have not been demonstrated in them, suggesting that the hair may have been introduced from outside the cyst. Pilonidal disease was a common problem among servicemen during World War II, thought to be due to the mechanical trauma of riding in jeeps, trucks, and tanks.