Perifolliculitis Capitis Abscedens et Suffodiens

Updated: May 16, 2022
  • Author: Malgorzata D Skibinska, MD, PhD; Chief Editor: Dirk M Elston, MD  more...
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Practice Essentials

Perifolliculitis capitis abscedens et suffodiens (PCAS, or dissecting cellulitis of the scalp) is a therapeutically challenging suppurative scalp disease of unknown etiology. Spitzer first described the disease in 1903, and Hoffman named it descriptively in 1907 (suffodiens is from the Latin suffodio, meaning to dig under). See Etiology and Pathophysiology, Treatment, and Medication. [1, 2]

PCAS is an uncommon disease. It occurs predominantly in black males (see the images below), in their second to fourth decade of life, but the condition also has been reported in other races and in women. Clinically, patients develop perifollicular pustules, nodules, and abscesses, with interconnecting sinus tracts that drain pus or blood. PCAS usually runs a chronic course with unpredictable relapses, although spontaneous resolution may occur. See Prognosis and Presentation. [3, 4, 5, 6]

Perifolliculitis capitis abscedens et suffodiens i Perifolliculitis capitis abscedens et suffodiens in a black man. Painful cutaneous nodules and patchy alopecia.
Side view of a black man with painful cutaneous no Side view of a black man with painful cutaneous nodules and patchy alopecia, characteristic of perifolliculitis capitis abscedens et suffodiens.

Etiology and Pathophysiology

The cause of PCAS has not been clearly defined. Risk factors have been evaluated, with current smoking strongly correlated with no clear linkage with obesity. [7] The disease is thought to result from occlusion of the pilosebaceous unit. Acne conglobata, hidradenitis suppurativa, and pilonidal cysts are frequent concomitant diseases, which, along with PCAS, are together referred to as the follicular occlusion triad (without pilonidal cysts) or tetrad. [5, 6]

With follicular occlusion, retention of material dilates the follicle, leading to rupture, with exposure of keratin to the skin and organisms. This, in turn, causes inflammation with a neutrophilic and granulomatous response. [3, 8, 9]

Bacterial infection likely develops secondarily, as most bacteriologic cultures are negative. The most frequently isolated pathogens are Staphylococcus aureus, S epidermidis, and S albus.

In 3 patients, keratosis-ichthyosis-deafness (KID) syndrome has been reported to be associated with the follicular occlusion triad. [10, 11, 12]

Anecdotal reports of associations between the follicular occlusion triad and pyoderma gangrenosum, as well as PCAS and Crohn disease, have been published. [13, 14]

In 2017, it was suggested that oily substances, exhaust gases, and anabolic steroids may be triggering factors in the development of PCAS in predisposed patients. [15, 16]



The prognosis for complete recovery from PCAS is poor. The disease is not life threatening, but it is chronic and relapsing. Complications can include the following:

  • Squamous cell carcinoma - Development is a possibility in chronic, relapsing lesions [8, 17]

  • Permanent alopecia - Occurs in chronically inflamed, scarred areas

  • Marginal keratitis - Has been described as a possible clinical association in patients PCAS [18]