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Dissecting cellulitis of scalp - Skin
See also in: Cellulitis DDx,Hair and Scalp
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Dissecting cellulitis of scalp - Skin

See also in: Cellulitis DDx,Hair and Scalp
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Contributors: Art Papier MD, William Van Stoecker MD
Other Resources UpToDate PubMed


Perifolliculitis capitis abscedens et suffodiens (PCAS), or dissecting cellulitis of the scalp, is a neutrophilic scarring alopecia with an abnormal inflammatory response to staphylococcal antigens. This association is linked to a propensity for follicular occlusion and dramatic secondary inflammatory changes to proinflammatory stimuli, such as bacterial infection. The follicle occludes, dilates, and ruptures, and the keratin promotes an inflammatory response in conjunction with a secondary staphylococcal infection attracting neutrophils.

The condition typically affects African-American men between the ages of 20 and 40, but it can occur in other races, in women, and in children (it has been reported in girls). PCAS usually affects the vertex (although the entire scalp can be involved), producing boggy or fluctuant pustules and nodules. Patients complain of pain and of a disfiguring appearance. If one presses on a nodule, pus or serosanguineous fluid may extrude from one or more of the orifices. The disease may wax and wane over several years, later producing dermal fibrosis, sinus tracts, and hypertrophic scarring with alopecia. There is an increased risk of squamous cell carcinoma in patients with long-standing disease.

PCAS may occur alone or as part of a follicular occlusion triad that includes acne conglobata and hidradenitis suppurativa or a tetrad including pilonidal cysts.

PCAS has been rarely associated with skull osteomyelitis.


L66.3 – Perifolliculitis capitis abscedens

77333008 – Dissecting cellulitis of scalp

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Differential Diagnosis & Pitfalls

Acne (folliculitis) keloidalis nuchae – presents on the occipital scalp and nape of neck with follicular papules and pustules. A skin biopsy reveals chronic inflammation, diffuse destruction of hair follicles, scarring, and fibrosis.

Folliculitis decalvans – presents on the occipital and vertex scalp with erythematous follicular papules and pustules with scarring and yellow-gray scale surrounding the follicle. There may be erosions, hemorrhagic crust, and tufted hair. A skin biopsy may reveal deep perifollicular or intrafollicular mixed infiltrate of lymphocytes, histiocytes, or plasma cells without abscess or sinus tract formation.

Cellulitis or erysipelas – in contrast to classic cellulitis, dissecting cellulitis of the scalp demonstrates prominent nodularity.

Pseudopelade of Brocq
Tinea capitis
Ruptured epidermoid cysts
Pilar cyst
Contact dermatitis
Fixed drug eruption
Mycobacterial infection
Erosive pustular dermatosis of the scalp

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Last Updated: 09/03/2013
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Dissecting cellulitis of scalp - Skin
See also in: Cellulitis DDx,Hair and Scalp
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Dissecting cellulitis of scalp : Painful skin lesions, Pustule, Scalp, Widespread scarring alopecia
Clinical image of Dissecting cellulitis of scalp
Confluent shiny nodules with associated scarring alopecia on the scalp.
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