Alopecia (Hair Loss)

Basics

Absence of hair where it normally grows
Categorized as acquired or congenital
- Most cases are acquired: Tinea capitis is most common, followed by traumatic alopecia and alopecia areata.
Also categorized as diffuse or localized
- Most cases of alopecia are localized and, of these, tinea capitis is the most common.
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.
Normally, about 50 to 100 hairs are shed and simultaneously replaced every day.
90% of alopecia cases are due to the following disorders:
- Tinea capitis
- Alopecia areata
- Traction alopecia
- Telogen effluvium
  - Alopecia is preceded by a psychologically or physically stressful event 6 to 16 weeks prior to the onset of hair loss.
  - Growing hairs convert rapidly to resting hairs.

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
Monilethrix (also called beaded hair)
- A rare autosomal dominant disorder

Trichotillomania is frequently associated with a finger-sucking habit.

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