Genetic Cystic Fibrosis What Are The Risks?
How can you know your risk of developing genetic cystic fibrosis? The first thing you need to realize is that cystic fibrosis (CF) is a genetic disease. Each human being has 23 pairs of chromosomes in each cell of the body. It is a mutation on the seventh pair that causes CF. This gene is very complex, and well over 1,000 different kinds mutations on this gene can manifest as CF. When two carriers have children, the risk that their CF genes will combine and that their offspring will have CF is one in four, or 25%. In addition, CF is an autosomal disorder, meaning that the CF gene can affect males and females equally
As a genetic disorder, it is passed along from parents to child. In the case of CF, two CF genes must be inherited, one from each parent. This makes CF a recessive disorder, because two genes are needed for the condition to manifest. While both of these parents, with their sole CF gene, would be healthy, they are still “carriers” of the condition.
Because of its recessive nature, the birth of a child suffering CF is frequently a complete surprise for a couple, since there are often no prior history of CF in the family.
This makes sense, because it is likely the gene has been passed on singly, and because of their good health, neither parent knew that he or she was a carrier.
One of the ways to evaluate your risk for having a CF mutation, even if you have no family history of the disease, Caucasian and Ashkenazi Jewish groups are at the highest risk, with a 1 in 3300 chance of having a child with CF. Hispanics follow, at 1 in 8000-9000, and African-Americans, at 1 in 15,3000. At lowest risk are Asian heritages, at 1 in 32,100.
If you are concerned that you might be a carrier of CF, a simple test for the gene can be performed using either a small blood sample or a cheek swab. Of the over 1,000 mutations, laboratories test for the most common – from 30 to 100. This means that the detection rate can vary.
Ashkenazi Jews get the most reliable results, at 97%. Caucasians have a 90% detection rate, and African-Americans 75%. The detection rate for Hispanics is 57%. The lowest detection rate is for Asians, at 30%. These variances occur because the mutations that cause CF vary around the world, and are more common in certain areas than others.
This means that, although CF carrier testing yields positive results, it is still possible to have a CF mutation. There are still more mutations that cause genetic cystic fibrosis that have not been discovered yet. For this reason, testing is recommended for anyone who has a family member who has manifested the disease, or whose partner either suffers from CF, has a family member with the disease, or who is a known carrier.