Alopecia areata

Alopecia areata is an autoimmune disorder in which immune cells attack hair follicles, causing patchy, nonscarring hair loss. It can affect the scalp, face, and other body sites.

Hair follicle immune privilege: A local state that limits immune recognition of structures within the hair follicle. Its collapse exposes follicle cells to immune attack in alopecia areata.
SALT score: A clinical measure estimating the percentage of scalp hair loss in alopecia areata. It quantifies scalp involvement and helps track treatment response.
Alopecia totalis: A form of alopecia areata involving complete loss of scalp hair. It represents extensive scalp involvement beyond isolated patches.
Androgenetic alopecia: A common patterned hair loss caused by genetic susceptibility and androgen effects on follicles. Unlike alopecia areata, it is not usually an autoimmune attack and causes follicle miniaturization.
CD8+ T cell: An immune cell that can recognize and destroy cells displaying specific antigens. Cytotoxic CD8+ T cells target hair follicles during active disease.
Dermoscopy: A skin examination method using magnification and illumination to reveal surface and follicular features. Characteristic hair and scalp findings can support diagnosis.
Alopecia universalis: A form of alopecia areata involving loss of hair across the entire body. It is the most extensive hair-loss pattern associated with the disorder.
Telogen effluvium: Diffuse hair shedding caused by a shift of many follicles into the resting phase. Its widespread shedding differs from alopecia areata’s discrete patches.
Interferon-gamma: An immune signaling protein that activates cells and promotes inflammatory responses. It helps drive the inflammatory signals that disrupt follicle immune privilege.
Skin biopsy: A procedure that removes a small skin sample for microscopic examination. Histology can help when the clinical pattern is uncertain.

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