to convert the essential amino acid tyrosine to
melanin. OCA type 1 features nearly complete
absence of pigmentation and usually legal
blindness (refractive correction can achieve
vision no better than 20/200).- OCA type 2 results from a mutation of the P
gene, which encodes proteins that participate in
pigmentation. OCA type 2 features moderate
pigmentation and moderate vision impairment
(usually correctable to 20/60). - OCA type 3 results from a mutation of the TRP-
1 gene, which encodes proteins that have
incompletely understood roles in the formation
of pigment.
Ocular albinism (OA) Ocular albinism results
from an X-linked mutation of an as-yet unidenti-
fied gene. People who have OA have normal or
minimally affected skin and hair pigmentation but
lack pigment in the structures of the eye, resulting
in vision impairment.
Other forms of albinism Other forms of
albinism are less common or may be part of a
larger complex of symptoms. Among them are
- Chédiak-Higashi syndrome (CHS), a variation
of OCA in which there are also immune and
neurologic dysfunctions - Hermansky-Pudlak syndrome (HPS), a multi-
system disorder that involves PLATELETdysfunc-
tion resulting in excessive bleeding, vision
impairment, and inappropriate fat storage in
tissues throughout the body as well as absence
of pigmentation in the skin and hair - Waardenburg’s syndrome, a complex of symp-
toms involving HEARING LOSS and partial
albinism (often a lock of white hair in the front
of the head with the rest of the hair normal
color); people with this disorder may also have
pale blue eyes or different color in each eye
Symptoms and Diagnostic PathThe most obvious symptom of albinism, pale col-
oration of the skin and hair, is apparent at birth.
Light-colored eyes and vision problems such as
STRABISMUS(inability of the eyes to focus in uni-
son), NYSTAGMUS (involuntary rapid eye move-
ments), and PHOTOPHOBIA(extreme sensitivity to
light) are common and also manifest early in
infancy.
The characteristic absence of pigmentation is
fairly conclusive for diagnosis of albinism. A thor-
ough OPHTHALMIC EXAMINATION with OPHTHAL-
MOSCOPYreveals the retina’s hypopigmentation. A
VISUAL ACUITY test demonstrates the degree of
vision impairment. GENETIC TESTING can identify
the causative gene mutation, which helps define
the inheritance pattern.Treatment Options and Outlook
There are no treatments for albinism itself. COR-
RECTIVE LENSESand methods to correct strabismus
or nystagmus, if present, can improve vision to
the extent possible. Many people who have
albinism have functional vision, even if they have
legal blindness, and can participate in most activi-
ties that require basic vision though may not be
able to drive.
Albinism, particularly OCA type 1, may limit
outdoor activities in areas that receive intense
sunlight. The sun presents a risk for sunburn and
related damage as well as harm to the eyes. Photo-
phobia nearly always accompanies albinism and
can make it difficult to remain in bright light, even
wearing sunglasses, for any substantial length of
time. People who have albinism should wear pro-
tective clothing, sunglasses, hats, and high-SPF
sunscreen whenever they are outdoors.Risk Factors and Preventive Measures
The sole risk factor for albinism is genetic muta-
tion. Doctors recommend genetic testing and
counseling for families in which members have
albinism. Though there is no treatment for
albinism, early diagnosis helps minimize the
extent of vision impairment that may result from
nystagmus or strabismus. People who have
albinism also should undergo frequent screening
for skin cancer, beginning in childhood.
See also AMBLYOPIA; MELANOCYTE.alopecia The clinical term for HAIR loss. There
are numerous forms and causes of alopecia, which
may be localized or widespread, temporary or per-
manent. Though alopecia is emotionally traumatic
for many people, it does not affect health in any
way though may reflect underlying health condi-136 The Integumentary System