Pilonidal Cyst Causes, Symptoms, Diagnosis, Treatment and Prevention by MedicineNet.com

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Pilonidal Cyst

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Medical Author: Steven E. Doerr, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

Pilonidal Cysts: What Are the Risk Factors?

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

Learn about pilonidal cysts, boils that form in the cleft of the buttocks. 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.

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What is a pilonidal cyst?

A pilonidal cyst is a fluid-filled sac (cyst) that develops along the tailbone (coccyx) near the cleft of the buttocks. These cysts usually contain hair and skin debris. The term pilonidal is derived from the Latin words pilus (hair) and nidus (nest). Individuals with a pilonidal cyst may not have any symptoms at all or they may develop infection of the cyst (pilonidal abscess) with associated pain and inflammation.

What causes a pilonidal cyst?

Though there are several theories, most researchers believe that pilonidal cysts are caused by the penetration of loose hairs into the skin. In response to this ingrown hair, a local inflammatory reaction causes a cyst to form around the hair. Excessive pressure or repetitive traumas to the sacrococcygeal area are thought to predispose individuals to develop the cysts. These conditions can also irritate existing pilonidal cysts. During World War II, more than 80,000 soldiers developed pilonidal cysts requiring hospitalization. Because so many of the afflicted servicemen rode in bumpy Jeeps for prolonged periods of time, it was termed "Jeep disease."

Who is at risk for developing a pilonidal cyst?

Pilonidal cysts occur more frequently in men than in women. They are also more common in Caucasians and in individuals who have an occupation that requires long periods of sitting. Pilonidal cysts usually occur in people between the ages of 15-24, and they are uncommon in people over the age of 40.

What are the signs and symptoms of a pilonidal cyst?

As previously mentioned, some individuals with a pilonidal cyst may not have symptoms, and the only finding may be a dimple or an opening in the skin (sinus tract) near the cleft of the buttocks. However, if the pilonidal cyst becomes infected (pilonidal abscess), the following signs and symptoms may develop: