Alopecia Areata

What is it?

Alopecia areata is an autoimmune disorder in which the body's immune system mistakenly attacks hair follicles, resulting in non-scarring hair loss (alopecia without permanent damage to follicles). The condition presents as well-demarcated, round or oval patches of hair loss that can occur on any hair-bearing area of the body, though the scalp is most commonly affected.

Who is affected?

Alopecia areata affects approximately 1 in 50 people (2% prevalence) at some point in their lifetime, with an estimated 204 million people affected worldwide.

• Prevalence: Lifetime risk of 1.7-2.1%; affects 1 in 50 people (2%) globally
• Age demographics: Can occur at any age; peak incidence between 25-35 years; higher prevalence in children (1.92%) than adults (1.47%)
• Gender distribution: Slightly more common in females, particularly with late-onset disease (after age 50)
• Risk factors: Family history of alopecia areata (10-20% have affected relatives); personal or family history of autoimmune conditions (thyroid disease, vitiligo, type 1 diabetes); atopic conditions (eczema, asthma, allergic rhinitis); psychological stress

What causes it?

Alopecia areata results from autoimmune dysfunction targeting hair follicles:

• Primary pathogenic mechanisms: T-lymphocytes (immune cells) infiltrate around hair follicles, disrupting the normal hair growth cycle; loss of immune privilege (protective barrier) that normally shields hair follicles from immune attack
• Genetic factors: Polygenic inheritance pattern with multiple susceptibility genes identified (PTPN22, CTLA4, IL2/IL21, HLA genes); approximately 10-20% have a family history of the condition
• Immunological dysfunction: Aberrant activation of CD8+ and CD4+ T-cells; elevated inflammatory cytokines (interferon-gamma, interleukins); disruption of JAK-STAT signaling pathway (key target for new treatments)
• Environmental triggers: Viral infections, vaccines, psychological or physical stress may precipitate onset in genetically susceptible individuals; seasonal variations noted in some cases

What are the clinical features?

Alopecia areata presents in several distinct patterns with varying severity:

• Patchy alopecia areata (most common): One or more well-circumscribed, round or oval patches of complete hair loss; smooth, non-scarring bald areas; exclamation mark hairs (narrow at base, wider at tip) at patch periphery
• Extensive forms: Alopecia totalis - complete loss of scalp hair; Alopecia universalis - complete loss of all body hair including eyebrows, eyelashes, and body hair; Ophiasis pattern - band-like hair loss along the sides and lower back of scalp
• Associated features: Nail abnormalities in 10-20% (pitting, trachyonychia or rough nails, longitudinal ridging); tingling or pruritus (itching) may precede hair loss; affected areas typically appear normal without inflammation or scarring
• Disease progression: Patches may spontaneously regrow or expand; new patches may develop while others are regrowing; highly unpredictable course with periods of loss and regrowth

How is it diagnosed?

Diagnosis is primarily clinical, based on characteristic presentation:

• Clinical assessment methods: Recognition of well-demarcated patches of non-scarring alopecia; identification of pathognomonic exclamation mark hairs; evaluation using dermoscopy (trichoscopy) showing yellow dots, black dots, broken hairs, and short vellus hairs
• Severity assessment: SALT score (Severity of Alopecia Tool) quantifies percentage of scalp hair loss: S0 (no loss), S1 (<25%), S2 (25-49%), S3 (50-74%), S4 (75-99%), S5 (100% loss)
• Laboratory tests: Usually unnecessary for diagnosis; thyroid function tests may be considered given association with thyroid disorders; biopsy rarely needed but shows peribulbar lymphocytic infiltrate ("swarm of bees" pattern)
• Differential diagnosis: Must distinguish from tinea capitis (fungal infection with scaling), trichotillomania (hair pulling with irregular borders), telogen effluvium (diffuse shedding), and secondary syphilis

What treatment options are available?

Treatment selection depends on age, extent of hair loss, and patient preference:

• FDA-approved JAK inhibitors (for severe cases): Baricitinib (Olumiant) - 2-4 mg daily for adults; approximately 40% achieve substantial hair regrowth at one year; Ritlecitinib (Litfulo) - 50 mg daily for ages 12 and older; both require ongoing treatment to maintain response
• Corticosteroid therapies: Intralesional injections (triamcinolone acetonide) every 4-6 weeks for limited patches; high-potency topical corticosteroids applied twice daily; oral corticosteroid pulses for rapidly progressive disease
• Contact immunotherapy: Diphenylcyclopropenone (DPCP) or squaric acid applied weekly to induce controlled allergic reaction; effective in 30-50% but requires indefinite treatment
• Emerging and adjuvant treatments: Topical minoxidil 5% solution as adjuvant therapy; anthralin cream for mild cases; phototherapy; platelet-rich plasma injections
• Prognosis and expected outcomes: Spontaneous regrowth occurs in 40% within 6 months and 50% within 1 year for first episode; extensive disease (>50% scalp) has lower remission rates (8% vs 68% for limited disease); recurrence is common - 85% experience relapse; hair may initially regrow white or gray before returning to normal color

Key points for patients

• Alopecia areata is an autoimmune condition, not contagious, and does not indicate poor health
• The course is unpredictable - hair may regrow spontaneously or with treatment, but recurrence is common
• New FDA-approved medications (JAK inhibitors) offer hope for severe cases previously difficult to treat
• When to seek medical attention: Rapid or extensive hair loss; associated symptoms like nail changes; significant emotional distress or impact on quality of life
• Support resources: National Alopecia Areata Foundation provides education and support; consider counseling for psychological impact; cosmetic options (wigs, scarves, makeup) available during treatment