Hair loss

Published on 10/03/2015 by admin

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Chapter 15 HAIR LOSS

Hair loss, or alopecia, can be classified in various ways, but the most common classification distinguishes nonscarring from scarring alopecia. The hair loss of scarring alopecia is permanent, whereas that of nonscarring alopecia usually is reversible. When a patient presents with hair loss, it is important to determine whether he or she is experiencing hair shedding, which is significant amounts of hair coming out, or hair thinning, in which more scalp is visible without noticeable amounts of hair falling out.

Every hair follicle goes through three phases: anagen (growth), catagen (transition between growth and resting), and telogen (resting). At any given time, approximately 85% of scalp follicles are in the anagen phase, and follicles remain in this phase for an average of 3 years. The catagen phase affects 2% to 3% of hair follicles at a time. The telogen phase occurs last, during which 10% to 15% of hair follicles undergo a rest period of about 3 months. At the end of telogen, the dead hair is ejected from the skin, and the cycle is repeated.

Alopecia areata is patchy hair loss of autoimmune origin. It usually occurs in well-circumscribed patches, but it also may involve the entire scalp (alopecia totalis) or body (alopecia universalis). The involved scalp may be normal, or subtle erythema or edema may be present. Short hairs that taper closer to the scalp surface, known as exclamation-mark hairs, are characteristic of alopecia areata. Alopecia areata may be associated with thyroid disease, vitiligo, or atopy. If a patient does not have any of these medical conditions and is otherwise healthy, no laboratory tests are necessary.

Androgenic alopecia, the most common form of alopecia in men and women, is also known as male-pattern balding, female-pattern balding, and common balding. Most patients with androgenic alopecia complain of thinning hair rather than shedding of hair. In some women, androgenetic alopecia may be a manifestation of hyperandrogenism; therefore, the history should focus on related signs such as menstrual irregularities, infertility, hirsutism, and acne. In an otherwise healthy woman with slowly progressive androgenetic alopecia and no signs or symptoms of hyperandrogenism, no laboratory testing is required.

Cicatricial alopecia results from a condition that damages the scalp and hair follicle. Examination typically reveals plaques of erythema with or without scaling. Syphilis, tuberculosis, acquired immunodeficiency syndrome (AIDS), herpes zoster, discoid lupus erythematosus, sarcoidosis, radiation therapy, and scalp trauma such as burns have been linked to cicatricial alopecia. If the cause of the disorder is not apparent, a punch biopsy of the scalp may be helpful in making the diagnosis.

Scarring alopecia represents a heterogeneous group of diseases manifested by erythematous papules, pustules, or scaling around hair follicles, resulting in eventual obliteration of follicular orifices.

Senescent (senile) alopecia is the steady decrease in the density of scalp hair that occurs in all persons as they age. Patients note a slow, steady, diffuse pattern of thinning hair beginning about age 50 years.

Syphilitic alopecia should be considered in every patient with unexplained hair loss. Hair loss may be rapid or slow and insidious and may be patchy (moth-eaten in appearance) or diffuse. Syphilitic alopecia is noninflammatory, nonscarring alopecia without erythema, scaling, or induration. However, in symptomatic syphilitic alopecia, the patchy or diffuse alopecia is associated with the papulosquamous lesions of secondary syphilis on the scalp or elsewhere.

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