Skin nontumor

Alopecia

Folliculitis decalvans



Last author update: 17 October 2023
Last staff update: 17 October 2023

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PubMed Search: Folliculitis decalvans

Chico J. Collie, M.B.B.S.
Jonathan D. Ho, M.B.B.S., D.Sc.
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Cite this page: Collie CJ, Ho JD. Folliculitis decalvans. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skinnontumorfolliculitisdecalvans.html. Accessed March 28th, 2024.
Definition / general
  • Folliculitis decalvans is a neutrophilic scarring alopecia characterized by pustules, perifollicular erythema and follicular tufting
Essential features
  • Neutrophilic scarring alopecia variant
  • More common in men
  • Presents with scarring alopecia, follicular pustules and resultant compound follicles that give the clinical appearance of tufting
  • Typical histologic findings include a dense neutrophilic and mixed inflammatory cell infiltrate involving the upper follicle with accompanying perifollicular and interfollicular fibrosis, loss of sebaceous glands and compound follicle formation
  • Staphylococcus aureus may be cultured from pustules but their pathogenic role is unclear
  • Untreated disease may result in extensive and irreversible hair loss
  • Reference: Dermatol Ther 2008;21:238
ICD coding
  • ICD-10: L66.2 - folliculitis decalvans
  • ICD-11: ED70.50 - folliculitis decalvans
Epidemiology
Sites
Pathophysiology
Etiology
  • Possible role for S. aureus
Clinical features
  • Patients frequently complain of pain, pruritus and a burning scalp sensation (Dermatol Ther 2008;21:238)
  • Presents with erythematous papules and pustules, which eventuate in patches of scarring hair loss
  • Pustules may be present around the periphery of scarred areas (Indian J Dermatol Venereol Leprol 2021;87:569)
  • Aberrant healing of destroyed infundibular epithelium results in numerous terminal hairs protruding from one follicular ostium (compound follicles or tufting)
  • Reported dermoscopic findings include a lack of follicular ostia, tufted hairs, perifollicular starburst pattern and yellow crusts (J Am Acad Dermatol 2021;85:1185)
  • Extensive scarring may be seen in longstanding disease
Diagnosis
  • History (sex, presence of pustules, location of hair loss)
  • Examination (findings as discussed above)
  • Biopsy
Prognostic factors
  • If untreated, may lead to extensive scarring (J Am Acad Dermatol 2021;85:1185)
  • Timely treatment in patients with visible remaining terminal or vellus hairs in involved areas may lead to retention of hair
  • Squamous cell carcinoma may occur at sites of longstanding, untreated disease (Dermatol Online J 2019;25:13030)
Case reports
Treatment
Clinical images

Contributed by Chico J. Collie, M.B.B.S. and Jonathan D. Ho, M.B.B.S., D.Sc.
Folliculitis decalvans affecting the vertex

Folliculitis decalvans affecting the vertex

Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Chico J. Collie, M.B.B.S. and Jonathan D. Ho, M.B.B.S., D.Sc.
Decrease in follicular density

Decrease in follicular density

Superior follicle

Superior follicle

Deep follicle

Deep follicle

Perifollicular infiltrate and follicular destruction

Perifollicular infiltrate and follicular destruction


Mixed inflammatory cell infiltrate

Mixed inflammatory cell infiltrate

Intrafollicular neutrophils

Intrafollicular neutrophils

Compound follicle

Compound follicle


Positive stains
  • Gram stain may reveal gram positive cocci in clusters consistent with S. aureus
  • Not routinely performed
Negative stains
  • PAS / GMS stains should be performed to exclude tinea capitis
Sample pathology report
  • Skin, scalp, punch biopsy:
    • Neutrophilic scarring alopecia consistent with folliculitis decalvans (see comment)
    • Comment: Transverse sections reveal 10 hairs in anagen and terminal in size. Sebaceous glands are markedly reduced in number. There is a moderately dense perifollicular, interfollicular and perivascular inflammatory cell infiltrate composed of neutrophils, plasma cells, lymphocytes and scattered eosinophils. Intrafollicular neutrophils with superficial pustule formation are seen. The inflammation increases in density towards the infundibulum. There is both concentric perifollicular fibrosis and interfollicular fibrosis. Fibrous tracts and naked hair shafts with a focal foreign body granulomatous reaction are present at deeper levels. Compound follicles in groups of up to 8 hairs are identified. The overlying epidermis is acanthotic and scale crust containing neutrophils are present. PAS stain is negative for fungal elements.
Differential diagnosis
  • Dissecting cellulitis / folliculitis of the scalp (perifolliculitis capitis abscedens et suffodiens) (Histopathology 2010;56:24):
    • Another form of neutrophilic scarring alopecia
    • Primarily in young black men with large pus filled nodules on the scalp and scarring alopecia
    • Bottom heavy mixed inflammatory cell infiltrate resembling granulation tissue in the deep dermis and subcutis
    • May have sinus tract formation
  • Tinea capitis:
    • PAS positive fungi within hair shafts
  • Central centrifugal cicatricial alopecia (Clin Cosmet Investig Dermatol 2016;9:175):
    • Black women
    • Progressive and symmetric peripheral expansion of the lesions
    • Lymphocyte predominant inflammatory cell infiltrate in the upper portion of the hair follicle
    • Perifollicular but no interfollicular fibrosis
    • With follicular rupture, occasional neutrophils may be seen but compound follicles of > 4 hairs are unusual in this entity
  • Lichen planopilaris / frontal fibrosing alopecia (Int J Dermatol 2006;45:375):
    • Patients with patches of scarring alopecia or loss of frontal hairline; more common in White women but may occur in persons of either sex and any race / ethnicity
    • Lymphocytic scarring alopecia
    • Perifollicular but no interfollicular fibrosis
    • Basal layer vacuolation of the follicular epithelium
Board review style question #1

A 25 year old man presents with hair loss involving the vertex of the scalp. Examination reveals numerous pustules, scarring and multiple hairs exiting through a single follicular ostium. A punch biopsy demonstrates the features shown in the associated photomicrographs. PAS stain is negative for fungal elements. What is the most likely diagnosis?

  1. Folliculitis decalvans
  2. Frontal fibrosing alopecia
  3. Lichen planopilaris
  4. Male pattern hair loss
  5. Tinea capitis
Board review style answer #1
A. Folliculitis decalvans. This is folliculitis decalvans, which is a neutrophilic scarring alopecia characterized by scarring alopecia, a neutrophilic / mixed inflammatory cell infiltrate and compound follicles (numerous hair shafts in one follicular ostium). Answers B and C are incorrect because frontal fibrosing alopecia and lichen planopilaris are lymphocytic scarring alopecias and do not typically present with pustules. Answer D is incorrect because pattern hair loss is a noncicatricial alopecia characterized by a decreased terminal to vellus ratio and retention of sebaceous glands. Answer E is incorrect because although tinea capitis may have a significant neutrophilic infiltrate and follicular destruction similar to folliculitis decalvans, the PAS stain should demonstrate fungi within hair shafts. Additionally, compound follicles are not a feature of tinea capitis.

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Reference: Folliculitis decalvans
Board review style question #2
Which of the following features favors folliculitis decalvans over dissecting cellulitis of the scalp?

  1. Concentric perifollicular fibrosis
  2. Decreased follicular density
  3. Loss of sebaceous glands
  4. Neutrophilic infiltrate involving the isthmus and infundibulum
  5. Premature desquamation of the inner root sheath
Board review style answer #2
D. Neutrophilic infiltrate involving the isthmus and infundibulum. While both folliculitis decalvans and dissecting cellulitis of the scalp are neutrophilic scarring alopecias, folliculitis decalvans involves the superior follicle while the latter involves the inferior follicle. Answers A, B, C and E are incorrect because the features listed are nonspecific may be seen in a variety of scarring alopecias.

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Reference: Folliculitis decalvans
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