56
Alopecias
• In a normal scalp, 90–95% of hairs are in anagen phase, 5–10% in telogen phase (Fig. 56.1).
Fig. 56.1 General concepts. A Hair follicle development and cycling. B Schematic of the scalp, showing frontal, temporal, and crown/vertex regions. A, Courtesy, Ralf Paus, MD; Anagen hairs, Courtesy, Maria K. Hordinsky, MD; Telogen hair, Courtesy, Leonard C. Sperling, MD.
• About 50–100 hairs normally shed daily.
• Alopecias can be categorized as diffuse vs. circumscribed, patterned vs. non-patterned, and non-scarring vs. scarring loss (Fig. 56.2).
Non-Scarring Alopecias
Male and Female Pattern Hair Loss (Androgenetic Alopecia)
• 80% of Caucasian men are affected by age 70 years.
• Women are less likely than men to have a family history of the disorder.
• Sensitivity of scalp hair to androgen hormones causes gradual miniaturization of hairs on the frontal/midline/vertex regions of men and the midline and crown of women (Fig. 56.3).
Fig. 56.3 Androgenetic alopecia. Comparison of partline on the crown (A) and the occiput (B). Courtesy, Leonard C. Sperling, MD.
• Should exclude hyperandrogenism (e.g. ovarian or adrenal source) in younger women or in women with signs of virilization (see Chapter 57).
Telogen Effluvium
• Sometimes a definable precipitating event ~3 months prior precedes diffuse shedding, leading to a reduced density of hair on the entire scalp and occasionally other areas of body hair (Table 56.1).
Table 56.1
Causes of telogen effluvium.
Some authors also propose vitamin B12 or iron deficiency as causes.
• Shed hairs are predominantly telogen hairs (Fig. 56.1).
• Generally complete hair regrowth occurs after months to years.
• Some women have chronic telogen effluvium without a definable cause.
• Rx: discontinue any potentially offending drugs, exclude thyroid abnormality and etiologies listed in Table 56.1.
Alopecia Areata
• Autoimmune disease with increased T-cells present in the hair matrix.
• Average lifetime risk for developing this disease is 1–2%.
• Circular to oval areas of alopecia that may progress to total scalp hair loss (alopecia totalis) or total body hair loss (alopecia universalis) (Fig. 56.4).
Fig. 56.4 Alopecia areata. A Circular area of alopecia in a child. B Exclamation point hair with the distal end broader than the proximal end. C Total alopecia of scalp, eyebrows, and eyelashes in a patient with alopecia universalis. D Ophiasis with a band-like pattern of hair loss along the periphery of the temporal and occipital scalp. E Diffuse variant of alopecia areata. F Typical yellow dots seen dermoscopically in alopecia areata. B, Courtesy, Julie V. Shaffer, MD; C, Courtesy, Leonard C. Sperling, MD; E, Courtesy, Maria K. Hordinsky, MD. F, Courtesy, Iris Zalaudek, MD.
• May see exclamation point hairs at borders (Fig. 56.4).
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