DermDx: Papular Lesions on the Scalp

Acne keloidalis nuchae (AKN) is a benign condition that occurs primarily in dark-pigmented men with coarse, curly hair. Although it has been reported in females, the ratio of male:female involvement is estimated to be 20:1. Additionally, it has been reported...

Submit your diagnosis to see full explanation.

Acne keloidalis nuchae (AKN) is a benign condition that occurs primarily in dark-pigmented men with coarse, curly hair. Although it has been reported in females, the ratio of male:female involvement is estimated to be 20:1. Additionally, it has been reported in people of Hispanic and Asian descent but to a much lesser degree. AKN was initially reported in the early 1800s as sycosis framboesiformis and was then reintroduced into the literature by Kaposi in 1869 as dermatitis papillaris capillitia. The term AKN was coined 3 years later by Bazin and is the most commonly used term to describe this condition.

AKN begins as a papular or pustular lesion primarily in the occipital region of the scalp. The pustular appearance of the lesions may be short-lived as the lesions are often deroofed by scratching or due to friction from hats or shirt collars. During this initial phase, lesions may be slightly pruritic. As the inflammation continues, papular or papulopustular lesions multiply and initial lesions grow in size. Finally, keloid-like plaques form, eventually leading to scarring alopecia. The areas of scarring alopecia may be centimeters in size to very large lesions covering the majority of the occipital region. Scarring alopecia represents a late disease stage and constitutes the most disfiguring and therefore distressing stage of disease. Tuft hairs or polytrichia along with broken hairs are often seen at the border of scarring alopecia. Tuft hairs constitute a few to more than 20 hairs exiting from a single hair follicle opening.

The cause of AKN is unknown but thought to be multifactorial. Though it begins as a folliculitis/perifolliculitis, it lacks an infectious or bacterial component separating it from bacterial folliculitis. It is associated with friction to the area (tights collars or fitted hats), close haircuts/shaving performed frequently, heat, and humidity. However, this is not thought to be the only cause, as acneiform associated with heat, friction, etc demonstrates equal incidence among black and white men.

Histologically, AKN begins as an acute perifolliculitis. The infiltrate is primarily mast cells. Mast cells are more likely to be seen normally in the posterior scalp than anterior scalp and may explain the pruritic clinical manifestation of early pustular appearance. As inflammation progresses, the hair follicle becomes weak and eventually is incapable of guiding the hair to the surface of the skin. The resultant effect is that the hair embeds below the skin surface and is consequently viewed as a foreign body. Granulomatous reaction to the perceived foreign body leads to fibroblastic activity. The resulting fibrosis further prevents the hair from reaching the follicular opening and continues the cycle of foreign body granulomatous reaction and resulting fibrosis. AKN also differs from acne in that there are no comedones seen in this process.

Diagnosis is typically made by visual recognition of the condition paired with key components of the patient’s history. Biopsy is typically unnecessary unless the clinician is unsure of the diagnosis. When biopsy is performed, punch biopsy is the preferred method while ensuring the sample depth is adequate to include the base of the follicle.

Patients should be educated to avoid picking or scratching lesions as bacterial superinfection can occur. They should avoid tight-fitting collars or hats and refrain from use of pomades and hair greases that may impair hair growth. Early treatment is the key to avoiding the significant disfigurement that can occur with keloid plaques and scarring alopecia. There is not one single effective treatment for AKN, and so patients should be prepared for trial and error of therapy. Class I or II corticosteroids with or without retinoic acid are believed to be effective treatments. Systemic steroids are effective at lesion reduction, but recurrence of the condition is common once the steroids are stopped. Risk outweighs the benefit of long-term systemic steroids for this condition. Intralesion corticosteroid injections can be effective and are indicated in patients who have persistent lesions refractory to topical therapy. In extreme cases, surgical excision of affected tissues or laser hair removal can be tried.

This patient obtained the correct diagnosis by visual recognition at the homeless clinic. He was treated with a Class I corticosteroid. He was advised to minimize behaviors that would exacerbate the condition. Because the patient was selecting his clothing from a clothing bank, discussion about shirt choices and fit were based on his unique living situation. The patient was extremely motivated to comply with therapy and visited the clinic weekly for follow-up. In addition to application of steroid therapy, he minimized haircuts and hair products. After 6 weeks of therapy, the patient had achieved a much improved appearance. The patient was eventually referred to a dermatology clinic after insurance was obtained.