Chapter 15 - Dissecting Cellulitis of the Scalp

Abstract

Primary neutrophilic cicatricial alopecias are a group of disorders that are characterized clinically by inflammation in the scalp, presenting usually as papules, nodules, pustules, and abscesses, resulting into areas of scarring alopecia, and histologically by mixed cell infiltrate. The most common diagnoses include folliculitis decalvans (FD), acne keloidalis nuchae, dissecting cellulitis of the scalp, and erosive pustular dermatosis of the scalp. They show overlapping clinical findings, but trichoscopy is a helpful tool for the differential diagnosis as some features are diagnostic, such as tufts of six or more hair in FD and 3D yellow dots with keratotic plugs (dissecting cellulitis). Histopathology is the ultimate tool for the diagnosis and is variable depending on stage of the disease: in general, early stages show mixed cell infiltrate with increased telogen count and later granulomatous infiltrates with perifollicular and interfollicular fibrosis. Therapeutic intervention as early as possible is mandatory to prevent disease progression and the development of subsequent cicatricial alopecia.