Definition
Alopecia areata is a disorder characterized by loss
of hair. Sometimes, this means simply a few bare
patches on the scalp. In other cases, hair loss is
more extensive. Although the exact cause is not known,
this is thought to be an autoimmune disorder in which
the immune system, the body’s own defense system,
mistakenly attacks the hair follicles, the tiny
structures from which hairs grow. Unpredictable hair
loss is the only noticeable symptom of this disorder.
Regrowth of hair may or may not occur. Hair loss is
usually confined to the head and face, although the
entire body may be involved.
Causes
There are several different hypotheses as to what causes
alopecia areata. Genetic factors seem to play an
important role since there is a higher frequency of a
family history of alopecia areata in people who are
affected. Alopecia areata appears to also have an
autoimmune factor causing the patient to develop
antibodies to different hair follicle structures.
Certain chemicals that are a part of the immune
system called cytokines may play a role in alopecia
areata by inhibiting hair follicle growth. Some studies
show that emotional stress may also cause alopecia
areata.
Hair loss occurs because the hair follicles in a
discreet area all enter the telogen or late catagen
stage of hair growth. In the catagen stage the hair
follicle stops growing and in the telogen stage it falls
out. Normally hairs are going through these stages at
random and the growing hairs on the rest of the head
outnumber the hairs that fall out. In alopecia areata,
something causes all the hairs in a certain area to
enter the telogen or catagen stage at the same time.
Symptoms
The primary symptom of
alopecia areata is roundish patches of hair loss on the
head, with smooth, hairless scalp in the affected areas.
Alopecia totalis involves the complete loss of all scalp
hair, and alopecia universalis is characterized by the
complete loss of all scalp and body hair.
Hairs that look like
exclamation points are sometime seen at the edges of a
bald patch.
Screening and Diagnosis
On occasion, a scalp
biopsy may be performed.
Treatment
No fully effective
treatments are available. Typical therapy includes:
-
Topical corticosteroids (medium to very high
potency)
-
Subcutaneous (under the skin surface) steroid
injection
-
Ultraviolet light therapy
Irritating agents may be
applied to hairless areas to promote regrowth
Expectations (prognosis)
Full recovery of hair is
common. However, alopecia areata occurring at a young age,
prolonged alopecia, or the presence of
eczema (atopic dermatitis) often predicts a poorer
outcome.
Complications
Permanent hair loss is a
possible complication of alopecia areata.
Other Hair Loss Conditions
Other diseases that may be mistaken for alopecia areata
include:
-
Telogen effluvium - generalized hair loss caused
by pregnancy, certain drugs, high fever, or stress.
-
Androgenic alopecia - also known as male-pattern
baldness.
-
Trichotillomania - manually pulling the hair out
caused by a psychological disorder.
-
Secondary syphilis - causing a "moth-eaten"
baldness pattern over the entire scalp.
