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Integumentary system ORGAN SYSTEMS

Alopecia areata

Non-cicatricial loss of hair in any area of the body, with a multifactorial autoimmune pathogenesis and an unknown etiology.


Types

  • Patchy alopecia areata
    • 1 or multiple separate or conjoined (reticular) patches of hair loss
  • Alopecia totalis
    • Total/near-total loss of hair on the scalp
  • Alopecia universalis
    • Total/near-total loss of hair on all haired surfaces of the body
  • Alopecia incognita
    • Diffuse total hair loss with positive pull test, yellow dots, short, miniaturized regrowing hairs, but without nail involvement
  • Ophiasis
    • Hair loss in a band-like shape along the circumference of the head (M/C along the border of the temporal and occipital bones)
  • Sisaipho
    • Extensive alopecia except around the periphery of the scalp
  • Marie Antoinette syndrome or canities subita
    • Acute episode of diffuse alopecia with very sudden “overnight” greying with preferential loss of pigmented hair

Pathophysiology

Hair cycle:

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Hair cycle: During the anagen phase (active growth period of hair follicle), which can vary from a few weeks to several years, epithelial cells in the hair bulb undergo vigorous mitotic activity and differentiate as they move distally to form the hair fiber and its surrounding inner root sheath and inner layer of the outer root sheath. Eventually, epithelial cell division ceases, and the follicle enters the catagen phase, in which the proximal end of the hair shaft keratinizes to form a club-shaped structure, which eventually sheds, and the lower part of the follicle involutes by apoptosis. The telogen phase marks the period between follicular regression and the onset of the next anagen phase (solid arrows). The development of the anagen follicle, which closely replicates embryonic development of the hair follicle, is conventionally divided into six stages (I–VI, with anagen VI representing the fully formed anagen follicle). In most mammals, hair cycles are coordinated in a wave-like fashion across the skin (moult waves), but in humans, follicles cycle independently of their neighbors. In alopecia areata (dashed arrow), anagen VI follicles are precipitated prematurely into telogen phase. Although they are probably able to re-enter anagen phase, the development of the follicle is halted at the anagen III/IV stage, when they prematurely return to the telogen phase. Truncated cycles may continue if and until disease activity declines, and follicles are able to progress further into the anagen phase. | Pratt, C. H., King Jr, L. E., Messenger, A. G., Christiano, A. M., & Sundberg, J. P. (2017). Alopecia areata. Nature Reviews Disease Primers, 3, 17011. Retrieved from https://doi.org/10.1038/nrdp.2017.11
alopecia-areata-pathogenesis-and-clinical-findings
The Calgary Guide | http://calgaryguide.ucalgary.ca/

Clinical features

Hair:

  • Non-scarring hair loss (round/oval patches)
  • Exclamation point hairs
    • Narrower along the length of the strand closer to the base, producing a characteristic “exclamation point” appearance
    • Very short (3-4 mm) and can be seen surrounding the bald patches
  • Greyer/lighter hair
  • Hair easily pluckable along the edge of the patch of hair loss (where the follicles are already being attacked by the body’s immune system) than away from the patch where they are still healthy.

Nails:

  • Pitting
  • Trachyonychia
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Clinical manifestations of alopecia areata: a) Limited patchy alopecia areata (50% scalp involvement). b) Extensive patchy alopecia areata (>50% scalp involvement). c) Active patch of alopecia areata showing exclamation point hairs (arrow) and slight skin erythema. d) Alopecia universalis. e) Ophiasis pattern of alopecia areata. f) Sparing of white hairs in alopecia areata. g) Nail pitting and longitudinal striations (trachyonychia) associated with alopecia areata. | Part c & f are reproduced with permission from REF 208, Wiley. Part e is reproduced with permission from REF 209, Springer. Part c & part f are reproduced with permission from Messenger, A. G., Sinclair, R. D., Farrant, P. & de Berker, D. A. R. in Rook’s Textbook of Dermatology 9th edn (eds Griffiths, C., Barker, J., Bleiker, T., Chalmers, R. & Creamer, D.) 89 (Wiley-Blackwell, 2016), Wiley. Part e is reproduced with permission from Bohm, M. in European Handbook of Dermatological Treatments (eds Katsambas, A. D., Lotti, T. M., Dessinioti, C, & D’Erme, A. M.) 45-53 (Springer Berlin Heidelberg, 2015), Springer

Diagnosis

Mainly clinical diagnosis

Investigations

Trichoscopy

  • Regularly distributed “yellow dots” (hyperkeratotic plugs)
  • Small exclamation-mark hairs
  • “Black dots” (destroyed hairs in the hair follicle opening)
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Diagnostic tools to validate and differentiate alopecia areata: a) Dermoscopy of the skin of patient with alopecia areata. Black arrowheads point to dystrophic, cadaverized and twisted hairs. The asterisk denotes a yellow dot with follicular plugging by keratinaceous debris. White arrows point to short, regrowing miniaturized hairs. b) Plucked exclamation point hairs are characterized by proximal hair shaft narrowing and are always broken; they might show reduced pigmentation. c) Histopathology of a vertical section of a skin biopsy from patch of alopecia areata with very early regrowth of hypopigmented hair. An early anagen hair bulb with vacuolar degeneration (arrows) of epithelial cells around the upper pole of the dermal papilla. d) A horizontal section from a similar area showing lymphocytic infiltrate (arrows) surrounding and infiltrating an anagen hair bulb. | Part b is reproduced with permission from REF 208, Wiley. Part c is adopted with permission from REF64, Wiley. Part b is reproduced with permission from Messenger, A. G., Sinclair, R. D., Farrant, P. & de Berker, D. A. R. in Rook’s Textbook of Dermatology 9th edn (eds Griffiths, C., Barker, J., Bleiker, T., Chalmers, R. & Creamer, D.) 89 (Wiley-Blackwell, 2016), Wiley. Part c is adapted with permission from Messenger, A. G., Slater, D. N. & Bleehen, S. S. Alopecia areata: alterations in the hair growth cycle and correlation with the follicular pathology. Br. J. Dermatol. 114, 337-347 (1986), Wiley

Histopathology (biopsy)

DEFINITIVE DIAGNOSIS

  • Peribulbar lymphocytic infiltrate (“swarm of bees“)
  • Inactive alopecia areata:
    • Pigment incontinence in the hair bulb and follicular stelae
    • Shift in the anagen-to-telogen ratio towards telogen

Management

  • Topical steroids
  • Steroid injections
  • Topical immunotherapy

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