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Genetic Counseling and VCFS: A Basic Review

Deborah Hung Copenheaver, M.S.

Children’s National Medical Center, Washington, D.C.

VCFS is a genetic disorder associated with a deletion of chromosome #22q11. Chromosomes are found in the cells of the human body and contain genes (or genetic information). This genetic information controls how a person looks and how the body develops and functions. Usually, there are 46 individual chromosomes arranged in 23 pairs and they are found in the cells of the body. Each parent contributes one chromosome to each pair.

There are 22 autosomal pairs of chromosomes and one sex-determining pair. Each chromosome can be divided in to two halves. The short half is called the p-arm while the long half is called the q-arm. The deletion that causes VCFS is found on the q-arm of chromosome #22. VCFS is an autosomal dominant disorder. Autosomal refers to the fact that the deletion is not found on the sex chromosomes and both males and females can be affected. Dominant means that only one of the chromosomes in the #22 pair needs to be affected in order to have the disorder.

In ~85-90% of cases of VCFS, the child is the first person in the family to have the disorder and there is no family history of the disorder. The mechanism of how and why a deletion occurs is not fully understood, but we do know that there is nothing that a parent does before or during a pregnancy that causes a deletion to occur. In the other ~10-15% of cases, one of the parents has VCFS and has passed it on to their child. Because the physical finding associated with VCFS can be subtle and vary from person to person, even within a family, often a parent does not know they have VCFS until their child is diagnosed.

When a person has the deletion in one of their #22 chromosomes, there is a 50% or 1/2 chance that they will pass on that chromosome to their offspring. There is also a 50% or 1/2 chance that they will pass on the non-deleted chromosome and their offspring will not have VCFS. Prenatal diagnosis is available to determine if a pregnancy is affected.

If your child has VCFS and you need help explaining inheritance or the diagnosis to them, your local genetic counselor may be able to help you.