This article is published for public interest. It should not be used for self diagnosis.
If you develop a scalp lesion, expert advice should be sought immediately.  

Acne Keloid

(syns. Acne keloidalis nucha, acne cheloidalis)

A skin condition commonly affecting curly haired Afro-males which presents as itchy follicular papules which enlarge and become keloidal. Common sites include the occiput (the scalp area between the ears). Follicular pustules (folliculitis) may exist. The scars are hairless. The condition may persist for many years.

The cause is not understood, but forms of dermatitis and acne are suspected. In most cases inflammation is caused by ingrowing hairs.

Treatment: not always successful.

Make sure clothing does not rub the back of the neck
Oral antibiotics if secondary infection exists.
Topical or intralesional steroids.
Laser vaporisation.
Surgery to remove affected skin