Tuesday, March 20, 2012


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Albinism is genetic condition most often characterized by a lack of pigment in a person’s eyes, hair, and skin. It is caused by inheriting a recessive gene from each parents, and occurs in approximately one in every 17,000 persons in the United States. While the condition is quite rare, one in seventy persons actually carries a recessive gene for a type of albinism. Two people who both have the recessive gene have a one in four chance that their child will have albinism. There are several different types of albinism, each with different characteristics. 

Oculocutaneous Albinism (OCA) 
Oculocutaneous albinism is the most common form of albinism and exists in many different forms OCA’s caused by a genetic mutation involving the enzyme tyrosinase which converts tyrosine into melanin. The first is referred to as OCA1a, and is sometimes called “complete albinism.” It is characterized by the body’s inability to change the amino acid tyrosine into melanin. People with OCA1a have no pigment, and have white hair, white skin and light blue, gray or violet eyes.

Oculocutaneous Albinism (OCA1b) 
The second variation of OCA1b, in which people develop some level of tyrosinase activity and detectable amounts of pigment, and can even tan slightly. The amount of pigment varies in different people, but most doctors agree that people with OCA1b have some observable pigment by the age of 2. If your child shows no signs of any freckling or darkening of his hair or eyelashes by the age of 2, he most likely has OCA1a.

Oculocutaneous Albinism (OCA2)
This is the most common form of albinism, and results from a mutation of a completely different gene that governs another enzyme for melanin production. People with OCA2 generally have slightly more pigment, and may have better vision than people with OCA1. There is no definitive way to tell whether your child has OCA1b or OCA2 without a genetic test, but the more pigment your child has the better her vision, the more likely it is she has OCA2.

Ocular Albinism (OA)
The term “ocular albinism” describes an inherited condition that differs from OCA in that the eyes lack melanin pigment, but the skin and hair show normal or near-normal coloration. With ocular albinism, the color of the iris of the eye may vary from blue to green or even to brown, and sometimes darkens with age. However, the light shines back through the eye upon examination, since very little pigment is present in the retina. The lack of pigment in the eye causes the same kinds of vision problems associated with other forms of albinism. In most cases, ocular albinism is X-linked, meaning that the gene that causes it lies on the X chromosome. X-linked ocular albinism occurs almost exclusively in makes. It is passed from mothers who carry the gene to their sons.

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