What is the pathophysiology of acne keloidalis nuchae (AKN)?

Updated: Nov 13, 2020
  • Author: Elizabeth K Satter, MD, MPH; Chief Editor: William D James, MD  more...
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Answer

The exact etiology of acne keloidalis nuchae (AKN) is unclear. It is thought that chronic irritation from coarse, curly hairs in the skin leads to inflammation and development of these lesions. This hypothesis is supported by the fact that close shaving and chronic rubbing of the area by clothing or athletic gear make AKN worse. In a study of 453 high school, college, and professional American football players, 13.6% of African American athletes had acne keloidalis nuchae, as opposed to none of the White athletes. [5] It has also been shown that men who have haircuts more frequently than once a month are at higher risk of developing acne keloidalis nuchae. [4, 6]

Pseudofolliculitis barbae (PFB) is a similar condition that occurs commonly in African Americans. In PFB, it has been proposed that close shaving of coarse, curved hairs facilitates the reentry of the free end of the hair into the skin (via either extrafollicular or transfollicular penetration), which then invokes a chronic foreign-body inflammatory response.

While ingrowing hairs may account for small papules, they do not sufficiently explain the progressive scarring alopecia that occurs in some patients. These patients with scarring alopecia often exhibit recurrent crops of small pustules and may have a condition akin to folliculitis decalvans. Chronic low-grade bacterial infection, autoimmunity, and some types of medication (eg, cyclosporine, diphenylhydantoin, carbamazepine) have also been implicated in the pathogenesis in some patients. [7, 8]

Sperling et al classify acne keloidalis nuchae as a primary form of inflammatory scarring alopecia and suggest that overgrowth of microorganisms does not play an essential role in the pathogenesis of AKN. They also found no association between pseudofolliculitis barbae and acne keloidalis nuchae. [9]


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