Pulmonologist Sarah Chalmers, M.D., answers the most frequently asked questions about cystic fibrosis.

Hello. I'm Dr. Sarah Chalmers, a pulmonologist at Mayo Clinic. And I'm here to answer some of the important questions you may have about cystic fibrosis.

Just because your baby's newborn screen came back positive does not mean that your baby has cystic fibrosis. Most babies who have a positive screening actually don't have CF. The newborn screen looks at a substance in the blood that is elevated in cystic fibrosis, but it can be elevated in other conditions as well, even premature birth. Some states also test for a gene mutation, but even if this comes back positive, it doesn't mean your baby has the disease. People with only one mutation are called carriers. It's very common in the United States and one in 20 people are CF gene mutation carriers. If your baby has a positive cystic fibrosis screen, they will need to see their doctor and have a sweat chloride test to see if they do have cystic fibrosis.

CF gene mutations are actually passed from parent to children in a specific pattern called autosomal recessive. Each parent passes one CF gene to their child, and therefore each person has two CF genes. To get the disease, both genes have to have a mutation. People with one CF gene are called carriers. If a parent is a carrier, there's a 50 percent chance they'll pass on the gene with a mutation to their child. If both parents pass on a normal gene, or only one parent passes a gene with a mutation, the child will not have CF. If both parents pass on a gene with a mutation, then the baby will have two genes with the mutation and will likely get the disease. If both parents are CF mutation carriers, there's a 25 percent chance that each one of their babies will be born with cystic fibrosis.

So both males and females can get cystic fibrosis. But females tend to have more symptoms, more lung infections, and they tend to start these symptoms of infections earlier in life as compared to males. No one knows for sure why this is so.

Actually, nearly 10 percent of cases of CF are diagnosed in adulthood. You're born with cystic fibrosis, but there are several reasons why it may not be diagnosed during childhood. Prior to 2010, some states didn't even screen for cystic fibrosis. So if you were born before 2010, you may not have received a newborn screening test for cystic fibrosis as a baby. Some gene mutations cause very mild disease and symptoms may go unnoticed until adulthood.

CF symptoms, how the disease affects the patient's organs and how it impacts their life is very different from one person to the next. Some people have very mild disease with only one organ affected and very few symptoms, while others have more severe disease with troublesome symptoms and multiple organs that are affected. Many factors including gene mutation type determine the impact on the patient. But your cystic fibrosis care team can work with you as an individual patient to create a personalized treatment plan that meets your individual needs.

Fertility is affected in both men and women with cystic fibrosis. Women with CF have thicker cervical mucus and they may also have irregular menstrual cycles. So it may take longer for women with CF to become pregnant. But most can become pregnant, have a normal pregnancy and a normal delivery. Almost all men with CF have infertility. Men with CF make normal sperm, but the sperm canal is absent. Because they still make sperm, assisted reproductive technologies can be used to help male CF patients have biologic children. Whether your children get CF or not depends on the combination of genes passed on from you and your significant other and can range from zero chance if neither parent has a gene mutation to a near 100% chance if both parents have CF.

Always be honest with your health care team. Let us know which medications you're taking and how often you're doing your treatments. Write down your questions before you come to your appointment so that we can make sure that we are meeting your needs. Thanks for your time. And we wish you well.

April 05, 2022