Hair Follicle Biology, the Sebaceous Gland, and Scarring Alopecias

Update on primary cicatricial alopecias

“…[26][27][28][29] Atrophy or destruction of sebaceous glands in early disease is a feature shared by many of the primary cicatricial alopecias that occur in humans and is a subject of active discussion. 30,31 This feature may result from direct immune-mediated destruction of sebaceous glands, diminished or arrested supply of clonogenic cells from an injured bulge, or as suggested by the Asebia model, from an intrinsic defect in sebaceous gland function.…”

Sebaceous gland loss and inflammation in scarring alopecia: A potential role in pathogenesis

“…This categorization distinguishes it from secondary SA, the result of follicular destruction caused by thermal burns, metastatic cancer, trauma, and radiation. 1 Hair loss may occur as a primary event characterized by folliculocentric inflammation with the ultimate replacement of the follicle by fibrous tissue. 1 Its classification depends on the pattern and the cells detected during the active phase of the disease.…”

“…1 Hair loss may occur as a primary event characterized by folliculocentric inflammation with the ultimate replacement of the follicle by fibrous tissue. 1 Its classification depends on the pattern and the cells detected during the active phase of the disease. Subtypes are classified as lymphocytic (lichen planopilaris [LPP], frontal fibrosing alopecia, chronic cutaneous lupus erythematosus, pseudopelade [Brocq], follicular degeneration syndrome [FDS], alopecia mucinosa, and keratosis follicularis spinulosa decalvans), neutrophilic (folliculitis decalvans [FD], tufted folliculitis, and dissecting cellulitis), and mixed (folliculitis acne keloidalis, folliculitis acne necrotica, and erosive pustular dermatosis).…”

“…5 The sebaceous glands are common victims along with the hair follicle in SA, and it is has been suggested that they are destroyed before the follicles. 1 The asebia mouse model 5,6 implicates sebaceous gland loss as a potential initiating event in SA. Inflammation of the sebaceous gland has also been a documented finding in previous reports, 2,3 although it has not been systematically evaluated and quantified.…”

Special Stains and Immunohistochemical Stains in Hair Pathology

“…60,61 Identifying a molecular mechanism that links sebaceous gland atrophy, inflammation, and permanent loss of hair follicles is likely to increase our understanding of cicatricial alopecia and guide development of target-oriented treatment. One such molecule, recently implicated as crucial for maintaining the epithelial stem cell compartment and the differentiation and maturation of sebocytes and the lipid homeostasis and control of inflammatory response, is the PPAR-g receptor.…”