Androgenetic alopecia |
Most common type of hair loss in both men and women |
Onset may be as early as puberty: 50% of men affected by age 50, 40% of women by age 70 |
Male pattern: Thinning of the frontal hairline, bitemporal recession, hair loss at the crown |
Female pattern: Hair loss at the crown with preservation of the frontal hairline |
Caused by the effect of dihydrotestosterone on hair follicles leading to miniaturization |
Alopecia areata |
Equally affects both sexes, with usual onset before age 30 |
Most common areas of hair loss are scalp and beard regions |
Round areas of complete hair loss with retained follicular ostia |
Exclamation point hairs found at the edges of expanding areas of hair loss are a hallmark sign |
Caused by autoimmune destruction of hair follicles involving cell-based and humoral immunity |
Telogen effluvium |
Acute telogen effluvium is characterized by diffuse scalp hair loss lasting <6 mo, whereas the duration is >6 mo for chronic telogen effluvium |
Women between ages 30 to 60 are most commonly affected |
A stressor event may or may not be present, usually occurring 2–4 mo before onset of hair shedding |
20%-50% of scalp hairs transition prematurely to telogen phase and are shed with normal hair shafts |
Anagen effluvium |
Diffuse hair loss characterized by hair breakage during anagen phase |
Classic causative agents are radiation therapy and cancer chemotherapy |
Affects 80%-90% of scalp hairs with onset within 1 −4 wk of exposure |
Narrowing, fractured hair shafts constitute a characteristic sign |
Loose anagen syndrome |
Typical patient is a blond female aged 2–5 who presents with diffuse hair loss and short, dull hair 6:1 Female to male ratio among the patient population, which includes adults and dark-haired individuals as well |
Greater susceptibility to hair breakage caused by premature keratinization of the inner root sheath, causing impaired adhesion with the hair shaft cuticle |
Shorter anagen phase leads to reduced hair length |
Trichotillomania |
Patients experience an irresistible urge to pull out their own hair despite negative impacts to their occupational and social function |
Childhood trichotillomania affects more boys than girls and resolves spontaneously |
Adult trichotillomania affects women much more frequently than men |
Often comorbid with mood or anxiety disorders |
Short, fractured hairs distributed sparsely and irregularly in affected areas |
Traction alopecia |
Results from tension applied to hair for a prolonged period of time, from hairstyles such as tight ponytails and braids, as well as hair-styling devices |
Areas under greatest pressure are most affected, usually scalp margins |
Especially common among African-American females because of their association with certain hairstyles |
Typically hair loss is transient; scarring or inflammation may be observed |
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Cicatricial alopecias |
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Chronic cutaneous lupus erythematosus |
Scaly, erythematous plaques with well-demarcated borders that eventually atrophy, found on sun-exposed areas including scalp |
Most common form is discoid lupus erythematosus, accounting for 50%-85% of all cases |
Affects more women than men, usually between ages 20–45 |
Associated with carpet tack sign, describing follicular spikes on the undersurface |
Cases among African-Americans are often more severe |
Lichen planopilaris |
Considered to be a variant form of lichen planus |
Classic lesions are smooth white areas with absent follicle ostia and central scarring; edges are characterized by erythema and scaling around hair follicles |
Mostly affects adult women at the crown and parietal areas of the scalp |
Due to autoimmune attack on hair follicles mediated by T lymphocytes |
Central centrifugal cicatricial alopecia |
Scarring hair loss that usually begins at the crown and expands outward to affect the entire scalp |
Middle-aged African-American females are most commonly affected; individuals of other races rarely present with this condition |
May be associated with chemicals and pressure applied to hair |
Lymphocyte-rich infiltrates observed at edges of balding lesions with signs of inflammation |