Cystic Fibrosis Genetics: Key Facts You Should Know

If you or a loved one has cystic fibrosis (CF), the first question is usually "why does this happen?" The answer lies in genetics, specifically changes in the CFTR gene. Understanding those changes helps you grasp how the disease shows up, how it spreads in families, and what you can do with modern testing.

How the CFTR Gene Affects the Body

The CFTR gene provides the instructions for a protein that controls the flow of salt and water in and out of cells. When the gene is normal, the protein keeps mucus thin and the lungs, pancreas, and other organs work smoothly. A mutation messes up that protein, turning mucus thick and sticky. This thick mucus blocks airways, leads to infections, and stops enzymes from reaching the intestines.

More than 2,000 CFTR mutations have been identified, but a handful accounts for most cases. The most common is called ΔF508 – it cuts off a piece of the protein, making it fold incorrectly. Knowing which mutation you have can guide treatment, because some medicines only work on certain defects.

Inheritance and Testing

CF follows an autosomal recessive pattern. That means you need two faulty copies – one from each parent – to develop the disease. If both parents carry a single mutated copy (they’re carriers), they usually feel fine, but each pregnancy has a 25% chance of resulting in a child with CF.

Carriers can find out through a simple genetic test that looks for common CFTR mutations. Testing is especially recommended if there’s a family history, if you’re planning a pregnancy, or if a newborn shows symptoms. Early detection lets doctors start therapies sooner, which can improve lung function and quality of life.

Newborn screening programs in Canada and many other countries already check for CF using a blood spot test. If the screen is positive, a sweat test confirms the diagnosis. The sweat test measures how much salt is in the sweat – people with CF have much higher levels.

For adults, a saliva or cheek swab can provide the same genetic information without needles. Many labs now offer panels that check for the most common mutations plus rarer ones, giving a comprehensive picture.

Knowing your specific CFTR mutation also matters for newer treatments called CFTR modulators. Drugs like ivacaftor, lumacaftor, and tezacaftor work by improving the function of the defective protein. They’re only approved for certain mutations, so the test result tells you whether you’re eligible.

Family planning options include pre‑implantation genetic diagnosis (PGD) during IVF, which lets embryos be screened for CF before implantation. This can prevent passing on two faulty copies while preserving the chance of having a biological child.

In short, cystic fibrosis genetics isn’t just science – it’s a roadmap for your health decisions. By learning how the CFTR gene works, what inheritance looks like, and which tests are available, you can take control of the disease, start the right treatments early, and make informed choices for your family.