Table 1.
Main features of various alopecias
| Noncicatricial alopecias |
|---|
| 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 |
| Cicatricial alopecias |
| 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 |