How Do You Make Sense Of The Results - Medicine and Health

If I am the mother of a child who has a full mutation in the fragile X gene, does that mean I'm a carrier?
Yes. Every mother of a child with a full mutation in the FMR1 gene is a carrier of a repeat at the pre-mutation or full mutation level.

If I test positive as a carrier, what does that mean for me?
A man or a woman who carries a fragile X pre-mutation will generally have normal intellectual abilities and a normal appearance, but a carrier of an FMR1 repeat is at risk of having some symptoms of fragile X syndrome. For example, among pre-mutation carriers:

21% of females experience premature ovarian failure (which can lead to infertility and a lack of normal female hormones).
Some older men develop tremors and an unsteady gait. This is known as fragile X Tremor-Ataxia Syndrome. Some people develop a mild learning disability. This would be someone with normal intelligence who has problems in a certain area, such as math or reading. They may need extra help in school.
How does being a fragile X carrier affect my family?
A woman who is a fragile X pre-mutation carrier has a 50% chance of passing the gene on to her children. When the gene is passed on, the number of repeats in the gene could stay the same or could increase.

A man who is a pre-mutation carrier has a 100% chance of passing the gene on to his daughters (because they always get his X chromosome) and no chance of passing the gene on to his sons (because they always get his Y chromosome, never his X). It is rare for the number of repeats to increase significantly when passed down from the father.

If the number of repeats stays the same, the child will be a pre-mutation carrier. If the number of repeats increases to more than 200, the child will have a full mutation. A boy who inherits a full mutation will have fragile X. A girl who inherits a full mutation will have fragile X about half of the time, but her symptoms will typically be milder.

Family members of a carrier are also at risk of having fragile X syndrome or passing it on to their future children.

For men:

If your father was a pre-mutation carrier, you cannot inherit the gene from him because the father only gives his X chromosome to his daughters.
If your mother was a pre-mutation carrier, you have a 50% chance of being a pre-mutation carrier (if you are not already affected).
If your daughter had a child with fragile X syndrome, you are almost certainly a pre-mutation carrier and at risk for developing fragile X Tremor-Ataxia Syndrome, the symptoms of which are tremors and an unsteady gait.
For women:

If your father was a pre-mutation carrier, you have inherited his affected gene. It is rare for the number of repeats to increase when passed down from the father, so you will most likely be a pre-mutation carrier also.
If your mother was a pre-mutation carrier, you have a 50% chance of being a pre-mutation carrier (if you are not already affected).
If your sister was a pre-mutation carrier, you have a 50% chance of being a pre-mutation carrier.
Could I get a positive test result, but not carry the disease gene (a false positive)?
The test for fragile X is highly accurate for the full mutation. False positives for a full mutation are unlikely. If the number of repeats ranges between intermediate and pre-mutation, it may be difficult to determine whether someone is a carrier. Each case must be interpreted individually.

Could I get a negative test result, but have a change in the gene that I could pass on to my children (a false negative)?


False-negative test results can occur if:

Only one DNA testing method (polymerase chain reaction [PCR] or Southern Blot) is used. On rare occasions, a person may appear to have a normal number of repeats according to the PCR test when they actually have an abnormal gene. The Southern blot test, however, will find the abnormal gene.
The number of repeats lies in the intermediate range. A lab cannot always provide a guaranteed interpretation for results that fall in the "gray zone" between normal