The word "albinism" refers to a group of inherited conditions. People
have little or no pigment in their eyes, skin, or hair. They have
inherited genes that do not
make the usual amounts of a pigment called melanin. One person in 17,000
has some type of albinism. Albinism affects people from all races. Most
children with albinism are born to parents who have normal hair and eye
color for their ethnic backgrounds. Albinism is found on the eleventh
chromosome, section q, loci 14-21.
Oculocutaneous albinism involves the eyes, hair, and skin. Ocular
primarily the eye. People with ocular albinism may have slight
lightening of hair and skin
colors as well, compared to other family members. At present researchers
have found 10
different types of oculocutaneous albinism, and five types of ocular
laboratory research studying DNA has shown that there are numerous types
of changes in
the genes of those with albinism, including within families.
The most common types of oculocutaneous albinism are called "ty-negative"
"ty-positive". Persons with ty-negative albinism have no melanin
pigmentation, and more
difficulty with vision. Those with ty-positive albinism have very slight
generally less severe visual difficulties. Tests were done on the hair
roots of individuals
with albinism, to tell these types of albinism apart. However, these
hair tests cannot
identify types of albinism, particularly in young children, whose
pigment systems are immature. Therefore hair tests are not helpful in
predicting the extent of visual disability of a child. "Ty-Neg" (also
called Type 1A) albinism results from a genetic defect in an enzyme
called tyrosinase. Tyrosinase helps the body to change the amino acid
tyrosine into pigment. The genetic defect that causes albinism in other
types of albinism is unknown, but it is speculated that it involves
other enzymes used to make pigment.
Albinism is passed from parents to their children through genes. For
types of albinism both parents must carry an albinism gene to have a
child with albinism.
Parents may have normal pigmentation but still carry the gene. When both
the gene, and neither parent has albinism, there is a one in four chance
at each pregnancy
that the baby will be born with albinism. This type of inheritance is
If a parent has a child with albinism, it means the parent must carry
gene. Until recently, unless a person has albinism or has a child with
albinism, there was no way of knowing whether he or she carries the gene
for albinism. Recently a test has been developed to identify carriers of
the gene for ty-negative albinism and for other types in
which the tyrosinase enzyme does not function. The test uses a sample of
blood to identify
the gene for the tryrosinase enzyme by its DNA code. A similar test can
identify ty-negative or similar albinism in unborn babies, by
People with albinism have very normal lives. They play sports, have
intelligence, and can have babies. The only difference between normal
people and albino
is that they don't have pigment in their skin.
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