Acne Keloidalis Nuchae (AKN)

Acne keloidalis nuchae (AKN) is a condition characterized by follicular-based papules and pustules that form hypertrophic or keloidlike scars. AKN typically occurs on the occipital scalp and posterior neck and develops almost exclusively in young, African American men.[1] The term acne keloidalis nuchae is somewhat of a misnomer because the lesions do not occur as a result of acne vulgaris, but rather a folliculitis. Moreover, histologically lesions are not keloidal, nor do the affected patients tend to develop keloidalis in other areas.[2]

Acne keloidalis nuchae was first recognized as a discrete entity in the late 1800s. Hebra was the first to describe and document this condition in 1860, under the name sycosis framboesiformis. Subsequently in 1869, Kaposi described this same condition as dermatitis papillaris capillitii.[3] The term acne keloidalis was then given to this condition in 1872 by Bazin, and, since that time, this is the name most often used in the literature.[2]

Lesions initially manifest as mildly pruritic follicular-based papules and pustules on the nape of the neck. Chronic folliculitis ultimately leads to development of keloid-like plaques. AKN develops in hair bearing skin areas, and broken hair shafts, tufted hairs, and ingrown hairs can be identified within and at the margins of the plaques themselves. Lesions can grow over time and become disfiguring and painful. In advanced cases, abscesses and sinus tracts with purulent discharge may develop. Unlike true acne vulgaris, comedones are not a common feature of AKN.[4]

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]

After extensive histological and ultrastructural studies of AKN lesions, Herzberg et al proposed that a series of events must happen in order for acne keloidalis nuchae to occur, namely the following[10] :

• 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.

• 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]

• Subsequently, fibroblasts deposit new collagen and fibrosis ensues.

• 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. 

Suggested etiologies include the following[1, 3, 4, 9, 12, 13, 14, 15, 16, 17] :

• Close shaving of the neck: This often exacerbates the condition. The sharp, curved hairs reenter the skin and invoke an acute inflammatory response.

• Constant irritation from shirt collars or athletic gear: This irritation causes shearing of the hairs.

• Chronic low-grade bacterial infections

• Use of antiepileptic drugs or cyclosporine

• An increased number of mast cells in the occipital region[18]

Reports have linked acne keloidalis nuchae (AKN) with keratosis follicularis spinulosa decalvans, a rare X-linked disorder in which individuals have a genetic predisposition toward follicular hyperkeratosis and subsequent inflammation.[19, 20]

Frequency

Acne keloidalis nuchae (AKN) is said to represent 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 and Asians, 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.[4, 11, 13, 21]

Age

Most cases occur in persons aged 14-25 years. Lesions manifesting prior to puberty or in persons older than 50 years is unusual.[4, 9]

The prognosis is good if acne keloidalis nuchae (AKN) is treated early and properly. 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.

Educate patients on the postulated underlying causes of acne keloidalis nuchae (AKN). Advise patients to discontinue wearing possible offending garments.Instruct patients to tell their barbers not to shave the posterior part of their hairline. Counsel patients about scalp folliculitis and how to care for it.

Importantly, note the duration of acne keloidalis nuchae (AKN), past therapeutic successes and failures, present medications, hair grooming techniques, and any known allergies. Regardless of symptomology, in general the lesions are cosmetically bothersome.

Early papular lesions are usually asymptomatic, but pustular lesions are often pruritic and occasionally painful. Large lesions can be painful. Abscesses and sinuses may be present and may emit purulent, malodorous discharge. Hats, shirts, jackets, and sweaters can irritate the involved area.

Early lesions manifest as firm, dome-shaped, follicular-based papules that are 2-4 mm in diameter. The papules are predominately located on the occipital region and nape of the neck. Pustules may be present, but often only excoriated papules can be identified because the lesions are often pruritic or they become traumatized when the hair is groomed.

As the disease progresses, more papules and pustules appear and, over time, can coalesce to form larger plaques. See the image below.

Numerous acne keloidalis papules and plaques in a white man with straight hair.

Ultimately, keloidlike plaques arranged in a bandlike distribution at or below the posterior part of the hairline can be identified. See the image below.

A large acne keloidalis plaque in a bandlike distribution at the posterior occiput in an African American man.

The plaques are usually only a few centimeters in diameter, but they can be greater than 10 cm in diameter. See the image below.

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).

Scarring alopecia eventually ensues. In chronic lesions, broken or tufted (“doll-like”) hairs may be seen within or at the periphery of the plaque. See the image below.

Numerous papules that have coalesced into a large plaque, within which are tufts of hairs with several hair shafts exiting the same follicular orifice.

Abscesses with draining sinuses also may be present.

Keloidlike plaques, scarring alopecia, chronic draining sinuses, and bacterial infection are complications of acne keloidalis nuchae (AKN).

Bacterial culture and sensitivity testing of acne keloidalis nuchae (AKN) lesions and draining sinuses should be considered. If pathogenic microorganisms are identified, appropriate antibiotics should be prescribed.

A biopsy may be performed if the clinical presentation is atypical and to exclude other similar conditions.

The histological findings vary depending on the timing of the biopsy. The initial infiltrate is primarily composed of neutrophils and lymphocytes that are distributed around the lower infundibulum and isthmus of the hair follicle. Subsequently, the follicle and sebaceous glands are destroyed, with liberation of the naked hair shafts into the dermis. Acute and granulomatous inflammation surrounds the free hair shafts, and, ultimately, fibrosis ensues. Scarring alopecia ensues in long-standing lesions, marked by dermal fibrosis associated with numerous plasma cells. True keloidal collagen is typically not a feature.

Often, acute and chronic inflammation may be present in the same region, because new lesions often develop adjacent to chronic lesions. Sinus tracks can be identified in long-standing lesions. Intact hair follicles at the margins may exhibit polytrichia, with more than one hair shaft noted in a single follicle, but this is physiologic for the occiput.[14] Individual early papules may also demonstrate ingrown hairs, and these may be seen clinically in patients without progressive scarring alopecia. See the images below.

A dense plasma cell infiltrate surrounding a hair follicle.

Naked hair shafts embedded within a fibrotic dermis.

Treatment of acne keloidalis nuchae (AKN) is difficult, and numerous modalities have been used with varying degrees of success. No single therapy has emerged as definitely first-line.[22]

The first step in management is education, which is key to preventing disease progression. Patients need to be made aware that the condition is exacerbated by short haircuts and close shaving. In addition, tight-fitting collared shirts, athletic head gear, and self-manipulation should be avoided since they may lead to mechanical shearing of the hairs.

Initiating therapy as quickly as possible after the initial appearance of lesions decreases the chance of long-term cosmetic disfigurement.[15] Topical antimicrobial cleaners/shampoos such as gentle foaming benzoyl peroxide washes or chlorhexidine can help prevent secondary infection.[11] Tar shampoos may provide an effective alternative. In addition, mild keratolytic agents containing alpha-hydroxy acids or topical retinoids may help soften the coarse hairs. Patients should discontinue hair greases or pomades, which can interfere with hair growth.[16]

Early, mild papular disease may respond to potent or superpotent topical steroids with or without the use of topical retinoids. This latter combination seems to be somewhat more effective than superpotent topical steroids alone.[17]

When pus or serous drainage is present, a culture should be taken. The use of a topical antibiotic (such as clindamycin) twice-daily may be advantageous to treat any bacterial superinfection. If active folliculitis is present, oral antibiotics such as doxycycline or minocycline should be used for several weeks to gain control over the inflammation. If active folliculitis persists or progresses despite adequate therapy, perform tissue culture and treat accordingly.

Intralesional triamcinolone acetonide injection can be helpful to reduce the size and firmness of papules and nodules. Doses range from 5 mg/mL up to 40 mg/mL for more firm and large lesions. Pretreatment anesthesia with topical lidocaine cream may reduce pain during injection. Alternatively, triamcinolone may be diluted in lidocaine to provide anesthesia with injection. Risks include skin atrophy and hypopigmentation. Liquid nitrogen may be administered to lesions to create edema and ease the injection process.[16]  Lesions may also be debulked by shaving or curetting prior to injection with triamcinolone.

In 2014, Okoye et al showed that targeted ultraviolet B (290-320 nm) phototherapy, 3 times weekly for 8 weeks, may improve the clinical appearance of fibrotic papules.[23]

In rare cases in which patients have large, inflamed lesions, a short course of oral corticosteroids may be considered.

Cryotherapy has also proven to be successful as monotherapy in some cases.[24] The area is frozen for 20 seconds, allowed to thaw, and is then frozen again 1 minute later. The process may be painful for patients, and the treated site often becomes hypopigmented because of destruction of the melanocytes and may remain so for up to 12-18 months.

Radiation therapy and intralesional 5-fluorouracil have been reported, but should only be considered for refractory cases.[25]

Once active disease is controlled, maintenance therapy can be used with a combination of topical retinoids, benzoyl peroxide gel or wash, and intermittent use of topical corticosteroids.

Laser ablation using various lasers (eg, carbon dioxide, 1064-nm Nd:YAG, 810-nm diode) should be considered for lesions refractory to other treatments.[26] One case series showed that 4 monthly laser hair epilation sessions using the diode laser (810 nm) in addition to a topical retinoid and steroid resulted in long-lasting improvement in the appearance and prevention of lesions. Laser hair epilation allows for coagulation necrosis of both viable hair follicles and fragmented hair shafts in the deep dermis.[27, 28, 29, 30]

Stable fibrotic lesions may be anesthetized with lidocaine and removed with punch biopsy or excision. The punch should extend deep into the subcutaneous tissue so that the entire hair follicle is excised. Superficial biopsies tend to have a much higher incidence of recurrence. After excision is performed, the wound edges can be injected with 10-40 mg/mL of triamcinolone acetonide to reduce inflammation. Silk sutures may be used to re-approximate the skin as they cause less of an inflammatory response than nylon sutures. Instruct patients to clean the postoperative area 3 times a day with a mild cleanser, followed by application of a topical antibiotic ointment. The sutures should be removed in 7-10 days, and the patient should then begin a twice-daily topical retinoic acid/corticosteroid regimen for 4-6 weeks.

The preferred method of excision for larger linear lesions (1 cm or less in diameter) is a horizontal ellipse with primary closure; however, excision by carbon dioxide laser and electrosurgery followed by secondary-intention healing are also viable options, especially for lesions that cannot be easily closed primarily.[11, 31]  The excision should extend below the hair follicles, and the area should be reapproximated with 4-0 silk sutures.

Always remember that when closing the area, ensure the patient’s neck is not in a flexed position; otherwise, the patient will spend a week or longer having to look upward.

An important caveat with surgical excision is that primary closure often results in recurrences and/or hypertrophic scarring, and data show that allowing lesions to heal by secondary intention results in fewer recurrences. Wound healing is typically achieved within 6-10 weeks, and, in general, the surgical site contracts to an area smaller and flatter than the original site.[32, 33]

Postoperative care is basically the same as that for punch grafts. Pain medication may be necessary for the first 48 hours.

Have patients return in 24-36 hours (preferably with the person responsible for changing dressings) for removal of the initial dressing. Soak the area with sodium chloride solution to facilitate the removal of the dressing and to clean the postoperative site.

Instruct patients to start cleaning the site twice a day (following the regimen above) once the dressing is removed. Instruct patients to return for follow-up in 1 week, or, sooner, if any complications occur.

Instruct patients to return for follow-up care for possible initiation of intralesional steroid injections or to begin topical steroid/retinoic acid therapy once the area has healed, usually in 2-3 months. Do not begin intralesional steroids prior to complete would healing because this can result in wound dehiscence.

A follicular papule or pustule occasionally develops along the border of the linear scar. Treat all inflammatory lesions with topical clindamycin until the infection subsides. The residual papule can then be treated with topical or intralesional steroids or excised via a punch biopsy.

Excision followed by grafting is typically not cosmetically acceptable because it results in a large, depressed, non–hair-bearing area.

Acne keloidalis nuchae (AKN) patients should avoid shaving the posterior part of the hairline close to the skin. Additionally, patients should discontinue wearing clothes or athletic gear that rubs or irritates the posterior parts of the scalp and the neck.

The goals of pharmacotherapy are to reduce inflammation and eliminate infection, if present.

Class Summary

These agents are used for their anti-inflammatory properties, but they must be used with caution because they have local and systemic adverse effects. Topical corticosteroids may be used alone or in combination retinoic acid.

Triamcinolone (Kenalog-10, Kenalog-40, Aristospan)

Triamcinolone can be used topically or injected intralesionally. It decreases inflammation by suppressing the migration of PMN leukocytes and reversing capillary permeability.

Prednisone

Prednisone may decrease inflammation by reversing increased capillary permeability and suppressing PMN activity. It is used when the patient has an acute flare.

Clobetasol propionate (Temovate, Clobex, Cormax)

Clobetasol propionate is a class 1, superpotent steroid that can be applied to the skin twice daily for 2 weeks. It comes in various formulations as solutions, lotions, creams, ointments, gels, and foams. Clobetasol propionate causes vasoconstriction, inhibits mitotic activity, and stimulates the synthesis of enzymes responsible for decreasing inflammatory reactions.

Halobetasol (Ultravate)

Halobetasol inhibits the initial manifestation of the inflammatory process, as well as the subsequent sequelae, which may include angiogenesis and fibroblast proliferation.

Fluocinonide (Vanos)

Fluocinonide is a class 2, potent topical steroid. It is available in various formulations, including a solution, cream, and ointment.

Class Summary

Although the exact mechanism of action for AKN is unknown, retinoids decrease the cohesiveness of abnormal hyperproliferative keratinocytes, modulate keratinocyte differentiation, and have anti-inflammatory properties.

Isotretinoin (Claravis, Amnesteem, Sotret)

Isotretinoin is an oral retinoid indicated for recalcitrant, nodulocystic acne. It addresses all four pathogenic factors involved the development of acne: follicular hyperkeratinization, inflammation, sebum production, and Cutibacterium acnes (formerly Propionibacterium acnes) growth. Treatment is weight-based, usually dosed initially 0.5 mg/kg and increased to 1 mg/kg. The total dosage ranges from 120-150 mg/kg and is achieved over 4-6 months. Patients must be registered into the government-regulated iPledge program in order to receive the medication.

Tretinoin topical (Retin-A, Avita, Refissa, Renova, Tretin X, Atralin)

Although the exact mechanism of action of tretinoin is unknown, retinoids decrease the cohesiveness of abnormal hyperproliferative keratinocytes, modulate keratinocyte differentiation, and have anti-inflammatory properties. Tretinoin topical is available as 0.025%, 0.05%, and 0.1% creams and 0.01% and 0.025% gels.

Adapalene (Differin)

Adapalene inhibits microcomedo formation. It normalizes keratinocyte differentiation in sebaceous follicles and it has anti-inflammatory properties. Adapalene is available as 0.1% gel, cream, and lotion and 0.3% gel..

Tazarotene (Tazorac)

Tazarotene inhibits microcomedo formation. It normalizes keratinocyte differentiation in sebaceous follicles and has anti-inflammatory properties. Tazarotene is available as 0.05% and 0.1 creams and gels.

Class Summary

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of this clinical setting.

Mupirocin (Bactroban, Centany)

Mupirocin is a topical antibiotic; it inhibits bacterial growth by inhibiting RNA and protein synthesis.

Doxycycline (Doryx, Adoxa, Monodox, Vibramycin)

Doxycycline is a broad-spectrum antibiotic with excellent gram positive coverage, including most resistant staph organisms. It inhibits protein synthesis and, thus, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria. Doxycycline may block dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.

Rifampin (Rifadin)

Rifampin inhibits RNA synthesis in bacteria by binding to the beta-subunit of DNA-dependent RNA polymerase, which, in turn, blocks RNA transcription.

Class Summary

Acne products are used for the treatment of mild to moderate acne vulgaris. These agents may have antibacterial and comedolytic properties. In severe cases, the agents may be used as an adjunct in therapeutic regimens.

Benzoyl peroxide (BenzeFoam, PanOxyl, Triaz, Neutrogena On The Spot, Invisible Acne Treatment, Acne Clear Maximum Strength)

Benzoyl peroxide is an oxidizing agent that possesses antibacterial properties and is comedolytic. Benzoyl peroxide is oxidized into benzoic acid with contact to the skin. It is available over the counter and by prescription. It can be used as a topical leave-on or wash-off product.