Is a progressive scarring alopecia.  It presents with small, smooth, firm bumps with occasional puss on the posterior scalp and nape of the neck.  Over time lesions result in scarring hair loss and keloid scars.  The exact cause is unknown.  Some associated factors include hair grooming, trauma, friction, heat, humidity, infections, and androgen hormones.  Treatment includes avoiding potential triggers (close shaving, frequent haircuts, shirts with high collars, helmets, chains, etc.), anti-inflammatories (topical and/ or injection), antimicrobials, destruction (liquid nitrogen, laser, etc), and surgery.

 

References: ​

- Maranda EL, et al.  Treatment of Acne Keloidalis Nuchae: A Systematic Review of the Literature. Dermatol Ther (Heidelb). 2016 Sep;6(3):363-78. doi: 10.1007/s13555-016-0134-5. Epub 2016 Jul 18. Review. ​

- Al Aboud DM, Badri T. Acne, Keloidalis Nuchae. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2018 Jan-.2017 Dec 3.