Med Insider
- Jul 17, 2022
- 3 min read

Cystic Fibrosis

By Jessica Raju

Highlights:

Cystic fibrosis (CF) is an inherited disorder that causes severe damage to the lungs, digestive system, and other organs in the body.
Cystic fibrosis occurs when both genes in the pair have a mutation.
A mutation in CFTR causes a dysfunction of the salt and water balance.
Seek immediate medical care if you're coughing up blood, have chest pain or difficulty breathing, or have severe stomach pain and distention.

Introduction: What is Cystic Fibrosis?

Cystic fibrosis (CF) is an inherited disorder that causes severe damage to the lungs, digestive system, and other organs in the body. Cystic fibrosis affects the cells that produce mucus, sweat and digestive juices. These secreted fluids are normally thin and slippery. But in people with CF, a defective gene causes the secretions to become sticky and thick. Instead of acting as lubricants, the secretions plug up tubes, ducts, and passageways, especially in the lungs and pancreas.

How does Cystic Fibrosis Occur?

Cystic fibrosis occurs when both genes in the pair have a mutation. A person with cystic fibrosis inherits one CF gene from each parent. Cystic fibrosis is a genetic disorder caused by inheriting a pair of genes that are mutated or not working properly. Everyone inherits two copies of the CFTR (cystic fibrosis transmembrane conductance regulator) gene. However, some of the inherited copies are mutations. To date, over 700 mutations of the CFTR gene have been identified. A person with CF inherits two mutated copies of the CFTR gene. These mutations can either be homozygous, the same, or heterozygous, different mutations. The most common mutation is delta F508, accounting for approximately 70% of all mutations. When each of the parents contributes a gene to their child, they could pass on either their CF gene or their non-CF gene. Each pregnancy could result in one of three outcomes:

A one in four (25%) chance that the child will have CF
A two in four (50%) chance that the child will be a carrier
A one in four (25%) chance that the child will not carry the CF gene

What does the Mutation Do?

The CFTR gene is a protein that functions as a chloride channel. A chloride channel helps maintain the proper balance of salt and water within a cell. A mutation in CFTR causes a dysfunction of the salt and water balance. This causes dehydration of the secretions (thick mucus) and excessive loss of salt in sweat.

Respiratory Signs and Symptoms

The thick and sticky mucus associated with cystic fibrosis clogs the tubes that carry air in and out of your lungs. This can cause signs and symptoms such as:

A persistent cough that produces thick mucus (sputum)
Wheezing
Exercise intolerance
Repeated lung infections
Inflamed nasal passages or a stuffy nose
Recurrent sinusitis

Digestive Signs & Symptoms

The thick mucus can also block tubes that carry digestive enzymes from your pancreas to your small intestine. Without these digestive enzymes, your intestines aren't able to completely absorb the nutrients in the food you eat. The result is often:

Foul-smelling, greasy stools
Poor weight gain and growth
Intestinal blockage, particularly in newborns (meconium ileus)
Chronic or severe constipation, which may include frequent straining while trying to pass stool, eventually causing part of the rectum to protrude outside the anus (rectal prolapse)

When to See a Doctor

If you or your child has symptoms of cystic fibrosis — or if someone in your family has CF — talk with your doctor about testing for the disease. Consult a physician who is knowledgeable about CF.

Cystic fibrosis requires consistent, regular follow-up with your doctor, at least every three months. Contact you doctor if you experience new or worsening symptoms, such as more mucus than usual or a change in the mucus color, lack of energy, weight loss, or severe constipation.

Seek immediate medical care if you're coughing up blood, have chest pain or difficulty breathing, or have severe stomach pain and distention.