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Traction
Alopecia
The natural history of AA is unpredictable. Extreme variations in duration and
extent of the disease occur from patient to patient.
• AA most often is asymptomatic, but some patients (14%) experience a burning
sensation or pruritus in the affected area.
• The condition usually is localized when it first appears. Of patients with AA,
80% have only a single patch, 12.5% have 2 patches, and 7.7% have multiple
patches. No correlation exists between the number of patches at onset and
subsequent severity.
• AA most often affects the scalp (66.8-95%); however, it can affect any
hair-bearing area. The beard is affected in 28% (males), eyebrows in 3.8%, and
extremities in 1.3% of patients More than one area can be affected at once.
• Localized
AA: Episodes of localized (<50% involvement) patchy AA usually are self-limited;
spontaneous regrowth occurs in most patients within a few months, with or
without treatment.
• Extensive AA: Extensive (>50% involvement) forms of AA are less common. AT or
AU were reported to occur at some point in 7% of patients; AA involving more
than 40% hair loss is seen in 11%. The proportion of patients with AT appears to
decrease with every decade of life.
o In 30% of patients with AT, complete hair loss occurred within 6 months after
onset of disease. Sharma reported a mean progression period to AT of 4 months
after onset. The natural evolution of AT is unpredictable, but recurrences of AA
(not necessarily AT) are expected.
o In a study
involving 736 patients, the relapse rate was 90% over 5 years. One percent of
children and 10% of adults can experience long-lasting regrowth. Forty-four
percent of children and 34% of adults experience a significant period of normal
or near-normal hair growth. Twenty-two percent of children and 34% of adults do
not experience regrowth.
• Associated conditions: Because some of the entities associated with AA occur
uncommonly in the general population, a large number of patients with AA need to
be examined to confirm whether an increased prevalence of these conditions
exists among patients with AA. Unfortunately, most studies are performed on
small groups; therefore, the data should be interpreted carefully.
o Atopic dermatitis is seen in 9-26% of patients with AA. In the general
population, the prevalence of atopic dermatitis in children in temperate
developed countries varies from 5-20%. In adults, the prevalence decreases to
2-10%. Some authors have found atopy to be a poor prognostic factor for AA.
o Vitiligo is seen with an incidence varying from 1.8-3% compared to 0.3% in
control subjects.
o Thyroid disease: Clinically evident thyroid disease was found in 0.85% of 1700
patients with AA. The prevalence of thyroid disease determined on a clinical or
laboratory basis varies among studies from 0.85-14.7%. The incidence of thyroid
disease in control subjects is estimated to be 0.17-2%.
o The presence of microsomal antibodies is found in 3.3-16% of patients.
Antibodies can be found with or without signs or symptoms of thyroid disease,
but patients with positive autoantibodies have a higher incidence of functional
abnormalities found on thyroid-releasing hormone tests (26% vs 2.8%). The
incidence of thyroid microsomal and thyroglobulin antibodies in control subjects
is 7%. Other studies have not supported these results. A study in 100 patients
with AA failed to find an increased incidence of circulating autoantibodies
including mitochondrial and thyroglobulin antibodies.
o Collagen vascular diseases have been found in 0.6-2% of patients with AA,
while the incidence in control subjects was 0.17%. The incidence of AA in 39
patients with lupus erythematous was 10% in a study by Werth et al, in contrast
to 0.42% of general dermatologic patients.
o Diabetes mellitus was found to be more common in control subjects (1.4%) than
in patients with AA (0.4%). The occurrence of AA may protect against the
appearance of insulin-dependent diabetes mellitus. However, the incidence of
type I diabetes mellitus was significantly higher in relatives of patients with
AA compared to the general population.
o Down syndrome: AA is seen in 6-8.8% of patients with Down syndrome, but only
0.1% of patients with AA have Down syndrome. The high frequency of AA in
patients with Down syndrome suggests that a genetic linkage for AA may exist on
chromosome 21.
o Emotional stress and psychiatric disease: Anxiety, personality disorders,
depression, and paranoid disorders are seen with increased incidence varying
from 17-22% of patients, and the lifetime prevalence of psychiatric disorders
was estimated to be 74% in patients with AA. Psychiatric problems are seen in
both children and adults. No association has been made between the severity of
the psychiatric disorder and that of AA.
o Stressful life events within the 6-month period preceding episodes of AA were
significantly higher in patients with AA compared to patients with androgenetic
alopecia or tinea capitis. Major stress factors (eg, death in family) were
reported in 12% of patients.
o Others associations: Pernicious anemia, myasthenia gravis, ulcerative colitis,
lichen planus, and Candida endocrinopathy syndrome also have been associated
with AA in some studies.
• Precipitating factors: A precipitating factor can be found in 15.1% of
patients with AA. Major life events, febrile illnesses, drugs, pregnancy,
trauma, and many other events have been reported, but no clear conclusions can
be drawn. Despite these findings, most patients with AA fail to report a
triggering factor preceding episodes of hair loss.
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