This patient found me on YouTube and drove a long way to see me. Thanks again to him for trusting his care with me and sharing his procedure to educate others. This condition is called Dissecting cellulitis of the scalp, also known as perifolliculitis capitis abscedens et suffodiens (PCAS). It is a neutrophilic scarring alopecia with an abnormal inflammatory response to staphylococcal antigens. It causes a propensity for follicular occlusion with secondary inflammatory changes to pro inflammatory stimuli such as ingrown hairs or bacterial infections. Some people just have scalp involvement others have a follicular occlusion tetrad with acne conglobata, hidradenitis suppurativa, and pilonidal cysts or sinuses. We found several long curled up hairs deep in the pocket of this abscess which probably caused the inflammatory cascade that led to the breakdown of fat tissue and fluid development in the area. Commonly the ones that have staph infections will be much more red, inflamed, and tender. Scalp abscess. Ingrown hairs. Incision and drainage. Dermatology procedure. Dermatology Physician Assistant. MrPopZit.