Pronounced: PIE-low-NIGH-dull sistEn Español (Spanish Version)
A pilonidal cyst is a fluid-filled developmental defect at the base of the spine.
The terms cyst, sinus, and abscess refer to different stages of the disease process.
- Cyst—not infected
- Abscess—pocket of pus
- Sinus—opening between a cyst or other internal structure and the outside
While the cyst is not serious, it can become infected and should therefore be treated. When a pilonidal cyst gets infected, it forms an abscess, eventually draining pus through a sinus. The abscess causes pain, a foul smell, and drainage.
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A pilonidal cyst may be congenital or acquired. If congenital, it probably began as a defect that existed when you were born. Sometime later, the defect allowed an infection to develop. If acquired, it may be the enlargement of a simple hair follicle infection or the result of a hair penetrating the skin and causing an infection.
Last reviewedAugust 2014by Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.