L00-L08: Infections of the skin and subcutaneous tissue

L05: Pilonidal cyst

A pilonidal cyst is a pocket typically located at the top of the crease of the buttocks, near the tailbone (coccyx). It's often filled with skin debris, hair, and other abnormal tissue. This condition occurs when loose hairs penetrate the skin, causing an immune reaction that results in cyst formation. Most frequently affecting young men, and especially those who sit a lot, such as drivers, pilonidal cysts can cause symptoms such as pain and redness at the base of the spine, fever, and drainage from the cyst with an unpleasant odor. If the cyst becomes infected, it may form into an abscess, causing extra pain and swelling. The cyst and abscess can grow over time and might recur even after treatment. This condition doesn't spread from person to person, but certain factors like excessive sitting, obesity, injury, and having a lot of body hair can increase the risk.