What Is Cystic Fibrosis?

Cystic fibrosis is a genetic disorder caused by inheriting two defective copies of the CF gene – one from each parent. Both parents must carry at least one defective gene, even if they do not have CF themselves.

People with only one defective gene are known as carriers. While carriers do not have CF, they can pass the gene on to their children. When two carriers have a child, the probabilities are:

• 25%: The child will have CF (inherits two defective genes).
• 50%: The child will be a carrier but will not have CF (inherits one defective gene).
• 25%: The child will neither be a carrier nor have CF (inherits no defective genes).

In people with CF, mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause the CFTR protein to malfunction. This faulty protein is unable to properly transport chloride, a key component of salt, to the surface of cells. Without chloride to draw water to the cell surface, mucus in various organs becomes thick and sticky.

Genetic testing for cystic fibrosis is incredibly important for several reasons:

1. Early Diagnosis and Treatment
   Genetic testing allows for early diagnosis, even before symptoms appear. Identifying CF in newborns or young children through genetic testing ensures that they can receive early treatment and interventions, which are crucial for improving long-term health outcomes. Early treatment can slow the progression of lung damage and help manage digestive issues.
2. Carrier Screening and Family Planning
   CF is an inherited disease, and both parents must carry a mutated CF gene for their child to have the condition. Genetic testing can identify carriers of the CF gene, allowing prospective parents to understand their risk of having a child with CF. This is important for family planning, giving couples the opportunity to explore options such as IVF with genetic screening, or adoption, if they carry the mutation.
3. Personalized Treatment Plans
   There are many different mutations of the CF gene (over 2,000), and the specific mutation a person has can affect the severity of the disease and how they respond to treatments. Genetic testing identifies the specific mutation, which can guide personalized treatment plans. For example, some newer drugs (such as CFTR modulators) are effective only for certain mutations, so genetic testing ensures the right medication is prescribed.
4. Research and Clinical Trials
   By identifying the specific CF mutation a person has, they may become eligible for clinical trials that target their mutation. Genetic testing also contributes to broader research efforts aimed at developing new treatments or even a cure for CF, as researchers need to study people with specific mutations to better understand the disease.
5. Family Risk Awareness
   If one child is diagnosed with CF, genetic testing can be done on siblings or other family members to determine if they are carriers or if they also have CF. This knowledge is essential for managing health and understanding the risks for future generations in the family.
6. Clarifying Symptoms
   Some people may experience symptoms of CF later in life or have milder symptoms that are atypical for the disease. Genetic testing can help confirm a CF diagnosis in these cases, especially when symptoms are unclear or if there is a family history of CF.
7. Insurance and Medical Decision-Making
   Having a genetic diagnosis can assist in accessing specialized care, insurance coverage for certain medications, and disability benefits. It provides a definitive answer, ensuring that the individual receives appropriate long-term medical care.

CF primarily impacts the respiratory, digestive, and reproductive systems. It is caused by mutations in the CFTR gene, which results in thick, sticky mucus that clogs airways and makes it harder for the body to clear infections. This mucus also affects the pancreas by blocking the release of digestive enzymes, leading to poor absorption of nutrients and malnutrition.

In people with CF, mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene disrupt the transport of chloride, an important component of salt, to the surface of cells. Without chloride, water cannot reach the cell surface, leading to the accumulation of thick mucus in various organs.

Respiratory System

In the lungs, thick mucus blocks airways, making it difficult to breathe and trapping bacteria, leading to chronic infections, inflammation, and respiratory failure. Germ avoidance is critical for people with CF.

• Symptoms: Persistent coughing, frequent chest infections, shortness of breath, and wheezing. As the disease progresses, scarring in the lungs can further reduce lung function.
• More Information: How Cystic Fibrosis Affects the Lungs

Digestive System

In the pancreas, mucus blocks the release of digestive enzymes, preventing proper digestion of fats and proteins. This leads to malabsorption, malnutrition, and poor growth.

• Symptoms: Greasy stools, difficulty gaining weight, and deficiencies in fat-soluble vitamins (A, D, E, and K). Damage to the pancreas can also result in cystic fibrosis-related diabetes (CFRD), a unique form of diabetes with features of both type 1 and type 2.
• More Information: Watch this video on CF and the digestive system

Reproductive System

CF often causes infertility in men due to the congenital absence of the vas deferens (CAVD), the ducts that transport sperm. In women, thickened cervical mucus can make conception more challenging, though many women with CF can still have children with appropriate medical support.

• More Information: Watch this video featuring Dr. Coward, a CF fertility specialist, or visit the Atlantic Reproductive website.

Sweat Glands

People with CF lose more salt through their sweat, which can lead to dehydration, heat stroke, and electrolyte imbalances, especially in hot weather or during physical activity.