Perifolliculitis Capitis Abscedens et Suffodiens 

Updated: May 16, 2022
Author: Malgorzata D Skibinska, MD, PhD; Chief Editor: Dirk M Elston, MD 


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]




Perifolliculitis capitis abscedens et suffodiens (PCAS) usually begins as a simple folliculitis, most often of the vertex and/or occiput, with clusters of perifollicular pustules rapidly followed by abscess and sinus formation.

Nodules range from a few millimeters to several centimeters in diameter and may be firm or fluctuant. Seropurulent fluid may be expressed from fluctuant nodules. Lesions may persist for years and frequently heal with a scarring alopecia. No systemic symptoms are usually evident. PCAS has a strong tendency to recur.

Physical Examination

PCAS most often affects the vertex and occipital scalp. The main physical signs, depending on the disease stage, are as follows[19, 20] :

  • Perifollicular pustules

  • Tender nodules: Some of these discharge pus or blood (see the first image below).

  • Intercommunicating sinuses between nodules

  • Patchy, scarring alopecia (see the second image below)

  • Dermoscopy of patches of alopecia in PCAS: Yellow dots, black dots, empty follicular openings, white dots, red dots, regrowing hair, and yellowish/whitish areas with an absence of follicular openings are seen. There is no unified opinion on trichoscopic features; however, they seem to correlate with disease activity and duration.[21, 22, 23]

A white patient with painful nodules. Image used w A white patient with painful nodules. Image used with permission from Medical Science Monitor, 2000, 6(3): 602-4.
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.

Shedding hair from the surface of nodules and sparing in between the inflamed areas can be observed and spondyloarthropathy has been reported. Regional lymphadenopathy is rarely noted.[24, 25]



Diagnostic Considerations

Conditions to consider in the differential diagnosis of perifolliculitis capitis abscedens et suffodiens (PCAS) include the following:

  • Acne keloidalis nuchae

  • Brocq pseudopelade

  • Tinea capitis[26]

  • Folliculitis decalvans

Alopecic and aseptic nodules of the scalp (AANS) is another disorder to consider in the differential diagnosis. According to a study by Abdennader et al, however, characteristics of AANS, including the occurrence of nonscarring alopecia, differentiate it from PCAS.[27]

Differential Diagnoses



Approach Considerations

Perform bacteriologic culture on pus from the discharging perifolliculitis capitis abscedens et suffodiens (PCAS) lesions in order to treat the secondary infection (primarily S aureus).

Histologic findings

The histopathologic picture of PCAS depends on the stage of the disease. Early lesions are characterized by a dense neutrophilic, lymphocytic, histiocytic, and plasma cellular infiltrate. Abscesses may be present in the dermis and even in the subcutaneous tissue. In later stages, chronic granulomas can be observed that consist of lymphocytes, plasma cells, and foreign-body giant cells. Scarring and fibrosis are frequently seen in the late stages. (See the image below.)[28]

Histopathologic picture of biopsy taken from a whi Histopathologic picture of biopsy taken from a white patient with perifolliculitis capitis abscedens et suffodiens. Hematoxylin and eosin stain, original magnification 400X. Image used with permission from Medical Science Monitor, 2000, 6(3): 602-4.


Approach Considerations

Perifolliculitis capitis abscedens et suffodiens (PCAS) is a chronic disease with an unpredictable course. Several medications are used to treat PCAS, but many give disappointing results.[5, 6]

Oral isotretinoin may be considered the treatment of choice.[29, 30, 31, 32] The successful use of oral acitretin and alitretinoin has also been reported.[33, 12] Successful treatment with topical isotretinoin (not available in the United States) has been described in 1 patient.[34]

Intralesional corticosteroids (eg, triamcinolone acetonide) can be injected into boggy nodules and sinus tracts to decrease inflammation. Their benefit, however, is short-lived; intralesional corticosteroids should be considered a temporizing measure.

According to case reports, antibiotics such as doxycycline, ciprofloxacin, rifampicin, and dapsone have been used successfully in PCAS.[35, 36, 37] Oral zinc sulfate has been used effectively in 2 patients,[38, 39] and biologic agents such as adalimumab and infliximab have also been successful.[40, 41, 42, 43, 44, 45, 46]

Compression therapy was reported as being effective in 1 patient.[47]

Laser ablation and epilation

Carbon dioxide laser ablation[48] and epilation of hair follicles with an 800-nm diode laser[49] and long-pulse non ̶ Q-switched ruby laser was tried in a single patient,[50] with good results. Repeated treatments with a long-pulsed Nd:YAG laser were used in 4 patients, with some improvement.[51]

Radiation therapy

Successful X-ray epilation has been reported.[52] Chinnaiyan et al reported good results in 4 patients with intractable PCAS who were treated with a modified form of external beam radiation.[53] A case report described improvement of PCAS with brachytherapy treatment.[54]

Surgical excision

Surgical excision of lesions should be considered in severe or recalcitrant cases. Wide excision of the affected areas and split-thickness skin grafting are favored by some as the treatment of choice.[55, 56, 57]

Photodynamic therapy

Treatment of PCAS with aminolevulinic acid photodynamic therapy (ALA-PDT) has been reported in single patients with conflicting results.5611 Cui et al report that photodynamic therapy combined with surgical treatment produced good results in 9 patients.[58]


People with PCAS taking isotretinoin should be seen monthly during therapy, and afterwards every 2-3 months. Additional appointments should be made if any sign of relapse appears.



Medication Summary

No single effective treatment is available for perifolliculitis capitis abscedens et suffodiens (PCAS), because the condition’s etiology is unknown.[59] Antibiotics are not a standard treatment, because bacterial infection is a secondary event. Intralesional steroid injections may be helpful in early stages of the disease.

Oral zinc sulfate[38, 39] was successful in 2 patients with PCAS, at 400 mg 3 times daily and 135 mg 3 times daily for 3 months. Successful treatment with topical isotretinoin (not available in the United States) was described in 1 patient.[34]

The best results have been reported with oral isotretinoin, which may be helpful in the follicular retention aspect of the disease (see the image below). A long course is considered to be the most effective treatment, with a daily dose of 1 mg/kg/day for approximately 4 months and then not less than 0.75 mg/kg for another 6-7 months. To avoid relapses, the treatment should be continued for approximately 4 months after the disease seems to be clinically inactive.[29, 30, 31, 32, 60]

A white patient with painful nodules after 3 month A white patient with painful nodules after 3 months of isotretinoin treatment. Image used with permission from Medical Science Monitor, 2000, 6(3): 602-4.

In addition, case reports have also been published on patients who were successfully treated with combinations of oral isotretinoin and rifampicin,[35] oral isotretinoin and dapsone,[36] infliximab,[40, 43, 44] adalimumab,[41, 42]  and risankizumab.[61]

Retinoid-like Agents

Class Summary

Decreased cohesiveness of abnormal, hyperproliferative keratinocytes may reduce the potential for malignant degeneration. Retinoids modulate keratinocyte differentiation and have been shown to reduce the risk of skin cancer formation in renal transplant patients.

Isotretinoin (Amnesteem, Claravis, Sotret)

Isotretinoin is an oral agent that treats serious dermatologic conditions. It is a synthetic, 13-cis isomer of naturally occurring tretinoin (trans-retinoic acid); tretinoin and isotretinoin are structurally related to vitamin A.

Isotretinoin is a first-line treatment for PCAS because of its influence on the pilosebaceous unit. It changes the pattern of keratinization of the follicle, has anticomedogenic effect, reduces the size and activity of the sebaceous glands, and reduces bacterial flora. It also has some anti-inflammatory effect.

A US Food and Drug Administration (FDA)–mandated registry is now in place for all individuals prescribing, dispensing, or taking isotretinoin. This registry aims to further decrease the risk of pregnancy and other unwanted and potentially dangerous adverse effects during a course of isotretinoin therapy. For more information on this registry, see iPLEDGE.