Occipital scalp papules in a teenage boy

Diagnosis: Acne keloidalis nuchae

Acne keloidalis nuchae is a chronic folliculitis that is characterized by smooth, dome-shaped papules on the posterior scalp and neck that become confluent, forming firm papules and hairless, keloid-like plaques.¹ Seen almost exclusively in young, postpubescent African American males, the condition is often asymptomatic, although some patients complain that the affected area itches. The cause of acne keloidalis nuchae may be associated with an acute pseudofolliculitis secondary to close-shaved curly hair reentering the skin; this leads to a foreign body reaction to hair protein and subsequent fibrosis.²

Differential Dx includes acne vulgaris

Acne keloidalis nuchae is diagnosed based on the appearance and location of the papules and keloid-like plaques as well as the patient’s history. The differential diagnosis includes acne vulgaris, hidradenitis suppurativa, and pseudofolliculitis barbae.

Acne vulgaris is a disorder of the pilosebaceous follicles primarily seen on the face, upper part of the chest, and back. Unlike acne keloidalis, it is characterized by the presence of comedones.^1,3

Hidradenitis suppurativa is characterized by secondary inflammation of the apocrine glands, which produces inflamed nodules and abscesses, primarily in the axillae, groin, and anogenital region.¹

Pseudofolliculitis barbae looks very similar to the initial presentation of acne keloidalis nuchae, and in fact, the pathophysiologic mechanism is the same. That said, pseudofolliculitis barbae occurs on the beard area and rarely produces keloidal papules.³