Sunday, March 6, 2011
How Prevalent is Albinism in the Population?
Recent statistics show that albinism affects 1 in 17,000 with some form of this inherited disorder. Albinism does not necessary affect lifespan, but it may be the complications form the disorder that may shorten lifespan, such as bleeding problems or lung disease.
What is the Chromosomal Abnormality in Albinism
Due to the fact Albinism is a chromosomal abnormality, "If a person is born to parents who both carry an autosomal recessive change (mutation), that person has a 1 to 4 chance of getting the malfunctioning genes from both parents and developing the disease. That person has a 50% (1 in 2) chance of inheriting one abnormal gene. The would make this person a carrier."
In other words, if four children are born to a couple who both carry the gene (but do not have signs of disease), the statistical expectation is as follows:
"The mutation of the gene is what actually causes the albinism."Each of these genes provides the chemically coded instructions for making one of several proteins involved in the production of melanin. Melanin is produced by cells called melanocytes, which are found in your skin and eyes. A mutation may result in no melanin production at all or a significant decline in the amount of melanin." That's why there are several different types of albinism.
There are five rare types of Albinism;
Oculocutaneous Albinism 3- which is caused by a gene mutation on chromosome 9 and has been primarily identified in black South Africans. People with this disorder usually have reddish-brown skin, ginger or reddish hair, and hazel or brown eyes.
Oculocutaneous Albinism 4- which is caused by a gene mutation on chromosome 5, and is a rarer form of the disorder. It is similar to type 2.
X-linked ocular albinism- is another type of rare albinism. It usually happens almost exclusively in males, and is a gene mutation on the X chromosome. People who have ocular albinism have the developmental and functional vision problems; but skin, hair, and eye color are generally in the normal range or slightly lighter than family members.
Hermansky-Pudlak syndrome- this is caused by one of at least seven mutated genes. People with this disorder have signs and symptoms like those of oculocutaneous albinism, but they also develop lung and bowel diseases and a bleeding disorder.
Chediak-Higashi syndrome- a mutation in a gene on chromosome 1. Signs and symptoms are also similar to those of oculocutaneous albinism. The hair is usually brown or blond with a silvery sheen, and the skin is usually creamy white to grayish. People with this syndrome have a defect with white blood cells that make them susceptible to infections.
In other words, if four children are born to a couple who both carry the gene (but do not have signs of disease), the statistical expectation is as follows:
- One child is born with two normal genes (normal)
- Two children are born with one normal and one abnormal gene (carriers, without disease)
- One child is born with two abnormal genes (at risk for the disease)
"The mutation of the gene is what actually causes the albinism."Each of these genes provides the chemically coded instructions for making one of several proteins involved in the production of melanin. Melanin is produced by cells called melanocytes, which are found in your skin and eyes. A mutation may result in no melanin production at all or a significant decline in the amount of melanin." That's why there are several different types of albinism.
There are five rare types of Albinism;
Oculocutaneous Albinism 3- which is caused by a gene mutation on chromosome 9 and has been primarily identified in black South Africans. People with this disorder usually have reddish-brown skin, ginger or reddish hair, and hazel or brown eyes.
Oculocutaneous Albinism 4- which is caused by a gene mutation on chromosome 5, and is a rarer form of the disorder. It is similar to type 2.
X-linked ocular albinism- is another type of rare albinism. It usually happens almost exclusively in males, and is a gene mutation on the X chromosome. People who have ocular albinism have the developmental and functional vision problems; but skin, hair, and eye color are generally in the normal range or slightly lighter than family members.
Hermansky-Pudlak syndrome- this is caused by one of at least seven mutated genes. People with this disorder have signs and symptoms like those of oculocutaneous albinism, but they also develop lung and bowel diseases and a bleeding disorder.
Chediak-Higashi syndrome- a mutation in a gene on chromosome 1. Signs and symptoms are also similar to those of oculocutaneous albinism. The hair is usually brown or blond with a silvery sheen, and the skin is usually creamy white to grayish. People with this syndrome have a defect with white blood cells that make them susceptible to infections.
How does a person inherit Albinism?
In this particular blog, I will educate you on the genetic disorder called Albinism. What is Albinism? It is a defect of melanin production, which is a natural substance that gives color to your skin, hair and the iris of the eye. Albinism makes the body unable to produce or distribute melanin in the body. There are two main types of albinism:
Albinism is an autosomal recessive disorder. This means two copies of an abnormal gene must be present for the disease or trait to develop; therefore Albinism is a chromosomal abnormality. It takes place when there is a mutation on one of the first 22 chromosomes. Since genes come in pairs, recessive inheritance means both genes in a pair must be defective to cause a disease. People with only one defective gene in the pair are considered carriers. However; they can still pass the abnormal gene to their children.
- Type 1 albinism is caused by a mutation in a gene on chromosome 11. Most people with this type have milky white skin, white hair and blue eyes.
- Type 2 albinism is due to a defect in a gene on chromosome 15. most people have yellow, auburn, or red hair and blue-gray or tan eyes.
Albinism is an autosomal recessive disorder. This means two copies of an abnormal gene must be present for the disease or trait to develop; therefore Albinism is a chromosomal abnormality. It takes place when there is a mutation on one of the first 22 chromosomes. Since genes come in pairs, recessive inheritance means both genes in a pair must be defective to cause a disease. People with only one defective gene in the pair are considered carriers. However; they can still pass the abnormal gene to their children.
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