Practice Essentials
Acne keloidalis nuchae (AKN) is a condition characterized by follicular-based papules and pustules that ultimately results in firm papules and keloid-like fibrotic plaques. Acne keloidalis nuchae most frequently involves the posterior neck and occipital scalp, and develops almost exclusively in young, African American men. [1] Although acne keloidalis nuchae is the name most often used in the literature for this condition, the term is a misnomer because this condition does not occur in association with, or as a complication of acne vulgaris, but rather occurs due to chronic and recurrent folliculitis and/or pseudofollicuilitis (ingrown hairs). Moreover, the lesions are not true keloids on histology. Lastly because this condition can also occur on the vertex scalp; therefore, some authors suggest using the term folliculitis keloidalis to more accurately describe this condition. [2, 9]
Lesions initially manifest as mildly pruritic follicular-based papules and pustules most commonly on the nape of the neck and ultimately the chronic inflammation results in development of keloid-like papules which often coalesce into plaques. Frequently within and at the edge of these plaques broken hair shafts, tufted hairs, and ingrown hairs can be identified. These plaques expand over time, are frequently painful and disfiguring. In advanced cases, abscesses and sinus tracts associated with purulent discharge may develop. Unlike acne vulgaris, comedones are not a common feature. [3]
Background
Acne keloidalis nuchae was first recognized as a discrete entity in the late 1800s. By report Hebra was the first to describe this condition in 1860, under the name sycosis framboesiformis. Subsequently Kaposi described this same condition as dermatitis papillaris capillitii in 1869, and then in 1872, Bazin used the term acne keloidalis which remains the most frequent name used to describe this condition in the literature [2, 9, 4]
Pathophysiology
The exact etiology of acne keloidalis nuchae (AKN) remains unknown; however, recurrent friction and/or minor trauma from clothing, athletic gear, use of CPAP and/or close shaving which often causes irregular shearing of hairs frequently contributes to the devlopment of this condition. This hypothesis is supported by a study of 453 high school, college, and professional American football players, 13.6% of African American athletes had AKN, as opposed to none of the White athletes. [5] It has also been shown that men who have close haircuts more frequently than once a month are also at higher risk of developing AKN. [3, 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 ingrown hairs may account for some of the small papules, this does not sufficiently explain the progressive scarring alopecia that occurs in some patients. Patients who develop scarring alopecia often exhibit recurrent crops of small pustules akin to folliculitis decalvans. Other factors which have been implicated in the pathogenesis of AKN include chronic low-grade bacterial infection, autoimmunity, and some types of medications such as cyclosporine, diphenylhydantoin, carbamazepine. [7, 8]
Sperling et al classified AKN as a type of primary inflammatory scarring alopecia and concluded overgrowth of microorganisms does not play an essential role in the pathogenesis. And even though pseudofolliculitis barbae and acne keloidalis nuchae have some overlapping clinical findings, most frequently occurs in African Americans and often have similar exacerbating factors, Sperling et al. concluded that AKN and PFB represent separate distinct entities. [9]
After extensive histological and ultrastructural studies of AKN lesions, Herzberg et al proposed that a series of events must happen in order for AKN to develop, namely the following [10] :
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The initial process begins as acute perifollicular inflammation followed by weakening of the follicular wall at the level of the lower infundibulum, the isthmus, or both.
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The naked hair shaft is then released into the surrounding dermis, which acts as a foreign-body and incites further acute and chronic granulomatous inflammation. This process is clinically manifested by small follicular-based papules and pustules. The nape of the neck has almost twice the number of mast cells compared with the anterior scalp and therefore may contribute to the pruritic sensation in this location. [11]
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Subsequently, fibroblasts deposit new collagen and fibrosis ensues.
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Distortion and occlusion of the follicular lumen by the fibrosis results in retention of the hair shaft in the inferior aspect of the follicle, thereby perpetuating the granulomatous inflammation and scarring. This stage is marked by plaques of hypertrophic scar and irreversible alopecia.
Etiology of AKN
Suggested etiologies include the following [1, 4, 3, 9, 12, 13, 14, 15, 16, 17] :
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Close shaving of the neck often exacerbates this condition due to development of ingrown hairs (sharp, curved hairs reenter the skin and invoke an acute inflammatory response).
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Constant irritation from shirt collars or athletic gear which results in irregular shearing of the hairs which subsequently become ingrown.
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Chronic low-grade bacterial infections and/or increased sensitivity to demodex
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Use of antiepileptic drugs or cyclosporine
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Androgen excess or increased sensitivity to androgens
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An increased number of mast cells in the occipital region [18]
Several reports have suggested that acne keloidalis nuchae (AKN) may be caused by a similar process to keratosis follicularis spinulosa decalvans which is a rare X-linked disorder that occurs in individuals with a genetic predisposition toward follicular hyperkeratosis and subsequent inflammation. [19, 20]
Epidemiology
Frequency
The exact incidence of this condition is unknown, but AKN is said to represent approximately 0.45% of all dermatoses affecting black persons. [12]
Race
Acne keloidalis nuchae is most prevalent in African Americans; however, it has occasionally been reported in Hispanics [21] and Asians [22] , and, rarely, in whites.
Sex
Although early literature inferred that acne keloidalis nuchae only affects males, it is now known to occur in females, with a male-to-female ratio of approximately 20:1. [3, 11, 13, 23]
Age
Most cases occur in persons aged 14-25 years. Lesions manifesting prior to puberty or in persons older than 50 years is unusual. [3, 9]
Prognosis
The prognosis is good if acne keloidalis nuchae is treated early; however, once major scarring develops, therapy is more difficult and morbidity is increased. The plaques of acne keloidalis nuchae slowly expand over time, and, although medically benign, acne keloidalis nuchae can be a psychologically devastating condition. Chronic pruritus and drainage may occur, and, ultimately, scarring alopecia may ensue.
Patient Education
Advise patients to avoid contributing factors such as discontinuing wearing potential offending tight fitting shirts, neck chains, or other tight garments around neck and use of head gear. Instruct patients to tell their barbers not to closely shave neck or occipital scalp. Use of keratolytic products such as salicyclic acid shampoo and/or acne wash containing salicylic acid or benzoyl peroxide, or use of topical retinoids can be helpful in reducing build of keratin within hair follicles and also slightly soften coarse hairs. If papules develop topical steroids can often be beneficial in reducing inflammation and use of topical antibiotic should be considered when pustules arise.
For patient education resources see Skin Conditions & Beauty Center and Folliculitis.
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Numerous acne keloidalis papules and plaques in a white man with straight hair.
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A large acne keloidalis plaque in a bandlike distribution at the posterior occiput in an African American man.
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A large acne keloidalis plaque on the occipital region in an African American patient. This man also had perifolliculitis of the scalp and acne conglobata (the follicular occlusion triad).
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Numerous papules that have coalesced into a large plaque, within which are tufts of hairs with several hair shafts exiting the same follicular orifice.
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A dense plasma cell infiltrate surrounding a hair follicle.
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Naked hair shafts embedded within a fibrotic dermis.
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