Pilonidal Cyst

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Pilonidal cysts facts

  • Pilonidal cysts occur along the tailbone near the cleft of the buttocks.
  • Pilonidal cysts are thought to develop from the penetration of hairs deep into the skin.
  • Pilonidal cysts can become infected.
  • An infected pilonidal cyst (pilonidal abscess) requires incision and drainage.
  • Recurrence of pilonidal cysts is common, and surgery may be required for more definitive management.

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, and sinus tracts may develop. Some individuals with a pilonidal cyst or sinus may not have any symptoms at all, whereas others may develop an inflammation of the cyst that leads to abscess formation with associated pain, redness, and irritation. Despite treatment, recurrence of pilonidal cysts is common.

Picture of a pilonidal cyst
Picture of a pilonidal cyst

Pilonidal disease was first described by Herbert Mayo in 1833, with R.M. Hodge coining the term pilonidal in 1880 from the Latin words pilus (hair) and nidus (nest). Extensive work into the treatment and management of pilonidal disease occurred during World War II, when nearly 80,000 U.S. soldiers were treated in U.S. military hospitals for this condition between 1941-1945. Because so many of the affected servicemen rode in Jeeps for prolonged periods of time, the condition also became known as "Jeep disease."

What causes a pilonidal cyst?

Though there are several theories as to the cause of pilonidal disease, most researchers now believe that pilonidal disease is acquired (rather than congenital) and that it is caused by the penetration of hair into deeper subcutaneous tissues through dilated hair follicles in the skin. In response to this irritation and perceived foreign material, the body produces a local inflammatory reaction, causing a cyst to form around the trapped hair. Excessive pressure, friction, and repetitive trauma to the sacrococcygeal area are thought to facilitate the entry of hair, thus predisposing individuals to develop pilonidal disease or irritate already existing pilonidal cysts.

Medically Reviewed by a Doctor on 4/30/2014

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Pilonidal Cysts: What Are the Risk Factors?

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.