Alopecia
(Hair Loss; Baldness)
Alopecia is defined as loss of hair from the body. Hair loss
is often a cause of great concern to the patient for cosmetic and psychologic
reasons, but it can also be an important sign of systemic disease.
Pathophysiology of Alopecia
Growth cycle
Hair grows in cycles. Each cycle consists of phases:
·
Anagen: A long (2- to 6-year) growing phase
·
Catagen: A brief (3-week) transitional apoptotic
phase
·
Telogen: A short (2- to 3-month) resting phase
At the end of the resting phase, the hair falls out
(exogen). Normally, about 50 to 100 scalp hairs reach the end of resting phase
each day and fall out. When a new hair starts growing in the follicle, the
cycle begins again.
Disorders of the growth cycle include
Anagen effluvium—a disruption of the growing phase causing
abnormal loss of anagen hairs
Telogen effluvium—significantly more than 100 hairs/day
going into resting phase
Classification
Alopecia can be classified as focal or diffuse and by the
presence or absence of scarring.
Scarring alopecia is the result of active destruction of the
hair follicle. The follicle is irreparably damaged and replaced by fibrotic
tissue. Several hair disorders show a biphasic pattern in which nonscarring
alopecia occurs early in the course of the disease, and then scarring alopecia
and permanent hair loss occurs as the disease progresses. Scarring alopecias
can be subdivided further into primary forms, where the target of inflammation
is the follicle itself, and secondary forms, where the follicle is destroyed as
a result of nonspecific inflammation (see table Some Causes of Alopecia).
Nonscarring alopecia results from processes that reduce or
slow hair growth without irreparably damaging the hair follicle. Disorders that
primarily affect the hair shaft (trichodystrophies) also are considered
nonscarring alopecia.
Some Causes of Alopecia
Etiology of Alopecia
The alopecias comprise a large group of disorders with
multiple and varying etiologies (see table Some Causes of Alopecia).
The most common cause of alopecia is
Androgenetic alopecia (male-pattern or female-pattern hair
loss)
Androgenetic alopecia is an androgen-dependent hereditary
disorder in which dihydrotestosterone plays a major role. The prevalence of
this form of alopecia increases with age, and it affects over 70% of men
(male-pattern hair loss) and 57% of all women (female-pattern hair loss) over
the age of 80 ( 1). The prevalence is lower in Asian and Black people than in
White people.
Androgenetic Alopecia
Androgenetic Alopecia
Other common causes of hair loss are
·
Drugs (including chemotherapeutic agents)
·
Infection (eg, tinea capitis, kerion)
·
Systemic disorders (disorders that cause high
fever, systemic lupus erythematosus, endocrine disorders, and nutritional
deficiencies)
·
Alopecia areata
·
Trauma
Traumatic causes include trichotillomania, traction
alopecia, burns, radiation, and pressure-induced (eg, postoperative) hair loss.
Less common causes are
·
Primary hair shaft abnormalities
·
Autoimmune diseases
·
Heavy metal poisoning
·
Rare dermatologic conditions (eg, dissecting
cellulitis of the scalp)
History
History of present illness should cover the onset and
duration of hair loss, whether hair shedding is increased, and whether hair
loss is generalized or localized. Associated symptoms such as pruritus and
scaling should be noted. Patients should be asked about typical hair care
practices, including use of braids, rollers, and hair dryers, and whether they
routinely pull or twist their hair.
Review of systems should include recent exposures to noxious
stimuli (eg, drugs, toxins, radiation) and stressors (eg, surgery, chronic
illness, fever, psychologic stressors). Symptoms of possible causes (eg,
fatigue and cold intolerance [hypothyroidism] and, in women, hirsutism,
deepening of the voice, and increased libido [virilization]) should be sought.
Other features, including dramatic weight loss, dietary practices (including
various restrictive diets), and obsessive-compulsive behavior, should be noted.
In women, a hormonal/gynecologic/obstetric history should be obtained.
Past medical history should note known possible causes of
hair loss, including endocrine and skin disorders. Current and recent drug use
should be reviewed for offending agents A family history of hair loss should be
recorded.
Physical examination
Examination of the scalp should note the distribution of
hair loss, the presence and characteristics of any skin lesions, and whether
there is scarring. Part widths should be measured. Abnormalities of the hair
shafts should be noted.
A full skin examination should be done to evaluate hair loss
elsewhere on the body (eg, eyebrows, eyelashes, arms, legs), rashes that may be
associated with certain types of alopecia (eg, discoid lupus lesions, signs of
secondary syphilis or of other bacterial or fungal infections), and signs of
virilization in women (eg, hirsutism, acne, deepening voice, clitoromegaly).
Signs of potential underlying systemic disorders should be sought, and a
thyroid examination should be done.
Virilization in women
Signs of systemic illness or constellations of nonspecific
findings possibly indicating poisoning
Interpretation of findings
Hair loss that begins at the temples and/or crown (vertex)
and spreads to diffuse thinning or nearly complete hair loss is typical of
male-pattern hair loss. Hair thinning in the frontal, parietal, and crown
regions is typical of female-pattern hair loss (see figure Male- and
female-pattern hair loss (androgenetic alopecia)). In androgenetic alopecia,
the central part width is wider on the crown of the scalp than it is on the
occipital scalp.
Hair loss that occurs 2 to 4 weeks after chemotherapy or
radiation therapy (anagen effluvium) can typically be ascribed to those causes.
Hair loss that occurs 3 to 4 months after a major stressor (pregnancy, major
febrile illness, surgery, medication change, or severe psychologic stressor)
suggests a diagnosis of telogen effluvium.
Manifestations of Hair Loss
Other than hair loss, scalp symptoms (eg, itching, burning,
tingling) are often absent and, when present, are not specific to any cause.
Signs of hair loss in patterns other than those described
above are nondiagnostic and may require microscopic hair examination or scalp
biopsy for definitive diagnosis.
Testing
Evaluation for causative disorders (eg, endocrinologic,
autoimmune, toxic) should be done based on clinical suspicion.
Male-pattern or female-pattern hair loss usually requires no
testing. When it occurs in young men with no family history, the physician
should question the patient about use of anabolic steroids and other drugs. In
addition to questions regarding prescription drug and illicit drug use, women
with significant hair loss and evidence of virilization should have levels of
appropriate hormones (eg, testosterone and dehydroepiandrosterone sulfate
[DHEAS]) measured (see Hirsutism).
The pull test helps evaluate diffuse scalp hair loss. Gentle
traction is exerted on a bunch of hairs (about 40) on at least 3 different
areas of the scalp, and the number of extracted hairs is then counted and
examined microscopically. Normally, < 3 telogen-phase hairs should come out
with each pull. If > 4 to 6 hairs come out with each pull, the pull test is
positive and is suggestive of telogen effluvium.
The pluck test involves sequentially pulling out about 50
individual hairs abruptly (“by the roots”). The roots of the plucked hairs are
examined microscopically to determine the phase of growth and thus help
diagnose a defect of telogen or anagen or an occult systemic disease. Anagen
hairs have sheaths attached to their roots; telogen hairs have tiny bulbs
without sheaths at their roots. Normally, 85 to 90% of hairs are in the anagen
phase, about 10 to 15% are in telogen phase, and < 1% are in catagen phase.
Telogen effluvium shows an increased percentage of telogen-phase hairs on
microscopic examination (typically > 20%), whereas anagen effluvium shows a
decrease in telogen-phase hairs and an increased number of broken hairs.
Primary hair shaft abnormalities are usually obvious on microscopic examination
of the hair shaft.
Scalp biopsy is indicated when alopecia persists and
diagnosis is in doubt. Biopsy may differentiate scarring from nonscarring
forms. Specimens should be taken from areas of active inflammation, ideally at
the border of a bald patch. Fungal and bacterial cultures may be useful.
Daily hair counts can be done by the patient to quantify
hair loss when the pull test is negative. Hairs lost during the first morning
combing or during washing are collected in clear plastic bags daily for 14
days. The number of hairs in each bag is then recorded. Scalp hair counts of
> 100/day are abnormal except after shampooing, when hair counts of up to
250 may be normal. Hairs may be brought in by the patient for microscopic
examination.
Treatment of Alopecia
Drugs (including hormonal modulators)
Laser light therapy
Surgery
Androgenetic alopecia
Minoxidil works by mechanisms that are not completely
understood to shorten the telogen phase, lengthen the anagen phase, and promote
growth in hair follicle diameter and length. Topical minoxidil (2% for women,
2% or 5% for men) 1 mL 2 times a day applied to the scalp is most effective for
vertex alopecia in male-pattern or female-pattern hair loss. However, usually
only 30 to 40% of patients experience significant hair growth, and minoxidil is
generally not effective or indicated for other causes of hair loss except
possibly alopecia areata. Hair regrowth can take 8 to 12 months. Treatment is
continued indefinitely because, once treatment is stopped, hair loss resumes.
The most frequent adverse effects are mild scalp irritation, allergic contact
dermatitis, and increased facial hair. Low-dose oral minoxidil in doses ranging
from 0.25 to 5 mg once/day is sometimes used off-label, but concerns about
cardiovascular adverse effects limit its use ( 1, 2).
Finasteride inhibits the 5-alpha-reductase enzyme, blocking
conversion of testosterone to dihydrotestosterone, and is useful for
male-pattern hair loss. Finasteride 1 mg orally once/day can stop hair loss and
can stimulate hair growth. Efficacy is usually evident within 6 to 8 months of
treatment. Adverse effects include decreased libido; erectile and ejaculatory
dysfunction, which may persist even after cessation of treatment (see Male
Sexual Dysfunction); hypersensitivity reactions; gynecomastia; and myopathy.
There may be a decrease in prostate-specific antigen (PSA) levels in older men,
which should be taken into account when this test is used for cancer screening.
Common practice is to continue treatment for as long as positive results
persist. Once treatment is stopped, hair loss returns to previous levels.
Finasteride is sometimes used off-label in women of nonchildbearing potential;
it is contraindicated in pregnant women because it has teratogenic effects in
animals.
Dutasteride, a drug used to treat benign prostatic
hyperplasia, is a stronger inhibitor of 5-alpha-reductase than finasteride and
is sometimes used to treat androgenetic alopecia.
Hormonal modulators such as oral contraceptives or
spironolactone may be useful for female-pattern hair loss.
Low-level laser light therapy is an alternate or additional
treatment for androgenetic alopecia that has been shown to promote hair growth.
Physician-dispensed and over-the-counter devices are available.
Autologous platelet-rich plasma injected into the scalp is
thought to contain growth factors that promote hair follicle growth and
maintenance ( 3).
Surgical options include follicle transplant, scalp flaps,
and alopecia reduction. Few procedures have been subjected to scientific
scrutiny, but patients who are self-conscious about their hair loss may consider
them ( 4).
Hair loss due to other causes
Underlying disorders are treated.
Treatment for alopecia areata includes topical,
intralesional, or, in severe cases, systemic corticosteroids, topical
minoxidil, topical anthralin, topical immunotherapy (diphenylcyclopropenone or
squaric acid dibutylester), or methotrexate.
Treatment for traction alopecia is elimination of physical
traction or stress to the scalp.
Treatment for tinea capitis is oral antifungals.
Trichotillomania is difficult to treat, but behavior
modification, clomipramine, or a selective serotonin reuptake inhibitor
(SSRI—eg, fluoxetine, fluvoxamine, paroxetine, sertraline, citalopram) may be
of benefit.
Scarring alopecia as in central centrifugal cicatricial
alopecia or dissecting cellulitis of the scalp is best treated with an oral
tetracycline plus a potent topical corticosteroid. Severe or chronic acne
keloidalis nuchae can be treated similarly or with intralesional triamcinolone;
if mild, topical retinoids, topical antibiotics, and/or topical benzoyl
peroxide may suffice.
Lichen planopilaris; its variant, frontal fibrosing
alopecia; and chronic cutaneous lupus lesions may be treated with drugs such as
oral antimalarials, topical or intralesional corticosteroids, topical or oral
retinoids, topical tacrolimus, or oral immunosuppressants.
Hair loss due to chemotherapy (anagen effluvium) is
temporary and is best treated with a wig; when hair regrows, it may be
different in color and texture from the original hair. Hair loss due to telogen
effluvium is usually temporary as well and abates after the precipitating agent
is eliminated.
Key Points
Androgenetic alopecia (male-pattern and female-pattern hair
loss) is the most common type of hair loss.
Concomitant virilization in women or scarring hair loss
should prompt a thorough evaluation for an underlying disorder.
Microscopic hair examination or scalp biopsy may be required
for definitive diagnosis.
Treatments include finasteride or dutasteride for
male-pattern hair loss, oral contraceptives or spironolactone for
female-pattern hair loss, and sometimes scalp injections with platelet-rich
plasma, follicle transplant, or other surgical procedures.
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