Inheriting Huntington's Disease: An Overview
Huntington's disease (also known as Huntington disease or HD) is a condition that is passed from parent to child through a defect (mutation) of the Huntington disease (HD) gene located on chromosome number 4. Huntington's disease is an autosomal dominant condition, which means that only one parent must have this gene in order for a child to inherit Huntington's disease. Although Huntington's disease is typically inherited, in a small number of cases, an individual with Huntington disease may not necessarily have a parent with the disorder.
Chances of Inheriting Huntington's Disease
Each parent has two copies of every chromosome but gives only one copy to each child. Therefore, each child of a person with Huntington's disease has a 50-50 chance of inheriting the Huntington disease gene. A person who inherits the Huntington disease gene, and survives long enough, will sooner or later develop Huntington's disease.
If a child does not inherit the Huntington disease gene, he or she will not develop Huntington's disease and cannot pass it to his or her children.
In some families, all the children may inherit the Huntington disease gene; in others, none do. Whether one child inherits the gene has no bearing on whether others will or will not share the same fate.
Is Huntington's Disease Always Inherited?
A small number of cases of Huntington disease are sporadic; that is, they occur even though there is no family history of Huntington's disease. These cases are thought to be caused by a new genetic mutation -- an alteration in the Huntington disease gene that occurs during sperm development.
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