Alopecia (Hair Loss)

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DESCRIPTION

  • Alopecia is the absence of hair where it normally grows.
  • Normally, about 50 to 100 hairs are shed and simultaneously replaced every day.
    • Hairs undergo cyclical growth with up to 90% in active growth, known as the anagen phase.
    • Up to 10% are dormant, known as the telogen phase where hair is shed after 2 to 3 months.
  • Of note, many normal healthy newborns lose their hair in the first few months of life.
    • Hair loss may be exacerbated by friction from bedding/sleep surface, especially in atopic infants.
  • Most cases are acquired.
  • Categorized as nonscarring or scarring (cicatricial)
    • Nonscarring types (follicle preserved): tinea capitis, alopecia areata, androgenic alopecia, traction alopecia, and telogen effluvium
    • Scarring types (destruction of hair follicle): permanent, due to uncommon inflammatory disorders that typically require biopsy for diagnosis. Tinea capitis and traction alopecia may lead to scarring alopecia if left untreated.
  • Also categorized by distribution
    • Focal/patchy: alopecia areata, tinea capitis
    • Patterned: male/female pattern hair loss
    • Diffuse: trichotillomania, telogen effluvium
  • 90% of alopecia cases are due to the following disorders:
    • Tinea capitis (ringworm)
    • Alopecia areata (autoimmune)
    • Traction alopecia (caused by constant tension on scalp hair)
    • Telogen effluvium (abnormal amount of hair transitions from anagen to telogen phase due to a stressor 6 to 16 weeks prior)
    • Trichotillomania (repetitive self-induced hair pulling)

RISK FACTORS

Genetics

  • Alopecia areata
    • Polygenic with variety of triggering factors
    • Family history in 10–42% of cases
    • Males and females equally affected
    • Onset usually before age 30 years and often follows a relapsing/remitting course
  • Monilethrix (also called beaded hair)
    • A rare autosomal dominant or autosomal recessive disorder that impacts hair follicle growth
    • Increased risk if personal or family history of other autoimmune conditions (e.g., vitiligo or thyroid disease)

COMMONLY ASSOCIATED CONDITIONS

  • Alopecia is associated with higher rates of anxiety/depression.
  • Alopecia areata is associated with other autoimmune conditions, including thyroid disease.
  • Trichotillomania is associated with a finger-sucking habit.

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