Alopecia Areata

Intro & Epidemiology - Patchy Hair Havoc

• Autoimmune, T-cell mediated, non-scarring hair loss targeting anagen hair follicles.
• Presents as well-demarcated, smooth patches of alopecia, often round or oval.
• Types:
  • Alopecia Areata (patchy): Most common; one or more coin-sized patches.
  • Alopecia Totalis (AT): Complete loss of scalp hair.
  • Alopecia Universalis (AU): Complete loss of all body and scalp hair.
• Epidemiology:
  • Lifetime risk: ~1.7-2%.
  • Peak incidence: Ages 20-40 years; can occur at any age.
  • Associations: Autoimmune diseases (thyroiditis, vitiligo), atopy, Down syndrome.

⭐ "Exclamation mark hairs" (short, <3-4 mm, broken hairs, tapered proximally) are pathognomonic, found at active lesion peripheries.

Pathophysiology - Immune System Mischief

• Autoimmune disease: T-lymphocyte mediated attack targeting anagen (growing) hair follicles.
• Key immune cells: Cytotoxic CD8+ T cells and Natural Killer Group 2D (NKG2D+) expressing cells.
• Pro-inflammatory cytokines: Interferon-gamma (IFN-γ) and Interleukin-15 (IL-15) are pivotal.
• Mechanism: Collapse of the hair follicle's immune privilege, leading to recognition of self-antigens.
• Genetic susceptibility: Strong associations with specific Human Leukocyte Antigen (HLA) alleles (e.g., HLA-DRB1, HLA-DQB1).
• Potential triggers: Viral infections, severe emotional or physiological stress; exact role varies.

⭐ Histologically, a perifollicular lymphocytic infiltrate around the anagen hair bulb, often described as a "swarm of bees," is characteristic (though not pathognomonic).

Clinical Presentation - Spotting the Spots

• Well-demarcated, round or oval patches of non-scarring hair loss.
• Affected skin is smooth, skin-colored, or slightly erythematous; no scaling.

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Diagnosis & Differentials - Sleuthing the Scalp

• Clinical Diagnosis:
  • Well-demarcated, smooth, round/oval patches of non-scarring hair loss.
  • Exclamation mark hairs (short, broken hairs, narrower at base) at periphery - pathognomonic.
  • Nail changes: pitting (most common), Beau's lines, trachyonychia.
• Dermoscopy (Trichoscopy):
  • Yellow dots (sebaceous gland openings).
  • Black dots (cadaverized hairs).
  • Broken hairs, exclamation mark hairs.
• Biopsy (Rarely needed):
  • Peribulbar lymphocytic infiltrate ("swarm of bees").
• Differential Diagnosis:
  • Tinea capitis (scaling, broken hairs, +KOH).
  • Trichotillomania (irregular patches, varying hair lengths, bizarre shapes).
  • Androgenetic alopecia (patterned loss).
  • Telogen effluvium (diffuse shedding).
  • Secondary syphilis ("moth-eaten" alopecia).

⭐ Alopecia Areata is an autoimmune condition often associated with other autoimmune diseases like thyroid disorders (Hashimoto's thyroiditis) and vitiligo.

Management Strategies - Taming the Tresses

• Goal: Arrest progression, induce regrowth. Choice based on age, extent, activity, duration.
• Limited Patchy AA (<50% scalp):
  • Intralesional corticosteroids (triamcinolone acetonide 2.5-10 mg/mL) q 4-6 wks. First-line.
  • Potent topical corticosteroids.
  • Topical minoxidil 5% solution/foam.
  • Topical immunotherapy (DPCP, SADBE) for refractory cases.
• Extensive AA (>50% scalp) / Rapid / Alopecia Totalis/Universalis (AT/AU):
  • Systemic corticosteroids (oral prednisone 0.5-1 mg/kg/day).
  • Systemic immunosuppressants (methotrexate, azathioprine).
  • JAK inhibitors (e.g., tofacitinib, baricitinib) - emerging.
• Counselling & camouflage (wigs).

⭐ Ophiasis pattern, nail involvement, early onset, and atopy are poor prognostic indicators.

High‑Yield Points - ⚡ Biggest Takeaways

• Alopecia Areata: An autoimmune T-cell attack on hair follicles, causing non-scarring hair loss.
• Key features: Patchy alopecia, pathognomonic exclamation mark hairs at patch edges.
• Associated with other autoimmune diseases like thyroiditis, vitiligo, and Down syndrome.
• Nail changes are common: Pitting (most frequent), trachyonychia (sandpaper nails), Beau's lines.
• Treatment: Intralesional corticosteroids for limited patches; topical immunotherapy (e.g., DPCP) for extensive disease.
• May progress to alopecia totalis (scalp) or universalis (body); spontaneous remission can occur.