Diseases and Disorders > Chronic Conditions

The Facts About Cystic Fibrosis

Find out how cystic fibrosis affects your sexual health.

An x-ray shows the human lungs glowing orange inside of a blue body.

Cystic fibrosis (CF) is a genetic disorder affecting about 35,000 people in the United States. With modern medicines and treatment, the average lifetime for someone living into adulthood with CF stands at 44 years.

What is cystic fibrosis?

This genetic disorder is an inherited condition, which means it's passed down from your parent's genes; you are born with it, you can't catch it. Cystic fibrosis can affect multiple organ systems, but the most debilitating effects manifest in the lungs, respiratory system and digestive system. It's usually diagnosed in newborns and is a lifelong disorder.

Cystic fibrosis affects the balance between salt and water in certain body areas, and this imbalance causes thick, sticky mucus to build up in the lungs, gut and parts of the digestive system. This buildup of mucus can lead to lung infections, blockages in the digestive system and difficulty getting nutrients to maintain a healthy weight.


A mutation (or error) in the cystic fibrosis transmembrane conductance regulator (CFTR) gene is the cause of CF. This gene helps control the movement of salt and water in and out of body cells. The CFTR protein is either malformed and cannot function properly or is not present at all.

Every person carries two CFTR genes, one from each parent. A faulty CFTR gene is carried by 1 in 25 people, but having one copy of the defective gene does not affect you. It's only when a baby inherits two faulty CFTR genes from their birth parents that they are born with cystic fibrosis.

Genetics and inheritance

Parents are often carriers of the defective gene and do not have CF themselves, so they may not realize they carry a faulty CFTR gene.

If both parents carry a defective CFTR gene, there is a 1 in 4 chance their baby will be born with cystic fibrosis. There is also a 1 in 2 chance the baby will be a CF carrier and pass on the faulty gene.

Additionally, there is a 1 in 4 chance the baby will be healthy, as in not being a carrier and not having cystic fibrosis.


In people without CF, the CFTR protein is created, moves to the cell surface and allows chloride and water to appropriately transfer in and out of the cell. If you have cystic fibrosis, this protein is faulty, thus, causing an imbalance in salt and water contents.

There are five classifications of cystic fibrosis, and scientists classify the different types based on how they affect the CFTR protein. The different types are:

  • Class 1: Shortened protein. This is where there's a problem with protein production resulting in a shortened CFTR protein that isn't functional.
  • Class 2: The protein is created but fails to reach the membrane. More than 85 percent of people with cystic fibrosis in Europe have this classification. The CFTR protein is not transported to the surface of the cells where it is required.
  • Class 3: The protein can't be regulated. Although the protein gets to the correct part of the cell, it doesn't open or close properly.
  • Class 4: Reduced chloride conductance. The protein changes shape, stopping chloride from traveling through the cell.
  • Class 5: Reduced protein levels. Quite simply, not enough CFTR proteins are created.

The different types of CFTR mutations are associated with varying disease complications and respond to different therapies.

How does cystic fibrosis affect the body?

In people with CF, their bodies can't move salt and water around the cells properly because of a faulty CFTR gene. This results in thick, sticky mucus building up in the lungs and digestive system.

There is always a layer of mucus inside the airways of your lungs, which ordinarily helps to trap and expel inhaled pathogens and irritants out of your lungs and airways. However, with cystic fibrosis, this layer becomes much thicker and stickier. Bacteria can get trapped in this sticky layer and may be difficult to expel through normal coughing or clearing mechanisms, leading to infections. Usually, your cilia—finger-like structures—in the lungs help move out mucus, but these often don't work correctly in people with CF. Over time, buildup of secretions and mucus containing bacteria, debris and irritants can lead to damage of the lungs and airways, and a failure to function normally for adequate oxygen and CO2 exchange.

Due to chronic infection and inflammation, people with cystic fibrosis often also suffer from nasal polyps and sinusitis. Similar to other lung conditions, CF often causes "clubbing" of the fingers, in which the ends of the fingers become swollen and rounder in shape.

Cystic fibrosis can also make bile—produced by the liver—thicker, which can lead to hepatobiliary problems.

Another problem for people with cystic fibrosis happens in the digestive system. The small tubes or ducts that transport digestive enzymes—involved in the breakdown of sugars, fats and proteins—out of the pancreas become blocked with mucus, so instead of reaching the digestive system, the enzymes build up in the pancreas, which becomes inflamed and may completely atrophy over time and stop producing these vital enzymes. People with CF may eventually be required to take enzyme supplements with their meals to help them digest food, which can lead to problems with growth and weight gain.

Other complications include brittle bones, diabetes and fertility problems.


There is no cure for cystic fibrosis, although new gene therapy treatments are under development, such as CRISPR gene editing technology. Treatment focuses on controlling the symptoms and attempting to reduce complications. A person with CF typically takes several medications, such as:

  • Antibiotics treat or prevent chest infections.
  • Bronchodilators help open airways and improve breathing.
  • Modulator drugs can significantly improve problems with the CFTR protein. These drugs are not suitable for everyone with cystic fibrosis but they are under development and improving all the time.
  • Mucolytics make mucus easier to clear.
  • Pancreatic enzyme replacement therapy assists with digestion.
  • Steroid medicine treats nasal polyps.

Other treatments include:

  • Dietary and nutritional advice to help avoid malnutrition.
  • Exercise to improve physical strength and overall health.
  • Regular physiotherapy and airway clearance techniques help clear the mucus from the lungs and airways.

In severe cases of CF, when the lungs begin to stop working, a lung transplant may be recommended.

How does cystic fibrosis affect the respiratory system?

The layer of mucus inside the airways of your lungs becomes much thicker and stickier if you have cystic fibrosis, trapping bacteria and leading to infections. Repeated infections make the airways inflamed and swollen, causing them to widen. This can lead to a condition called bronchiectasis, which impairs adequate air ventilation and can lead to permanent lung damage, so it is essential to treat lung infections aggressively.

Pulmonary fibrosis versus cystic fibrosis

Pulmonary fibrosis is not the same as cystic fibrosis; it is a completely different condition.

Pulmonary fibrosis is the buildup of scar tissue in your lungs. In some people, pulmonary fibrosis is due to the side effects of certain medications or exposure to particular dust or allergens. But in most people, the cause of pulmonary fibrosis remains unknown.

Cystic fibrosis and fertility

The defective CFTR protein in cystic fibrosis can lead to the failure of the vas deferens to develop. In turn, this leads to a complete absence of sperm in the seminal fluid. The vas deferens is part of the male reproductive system, carrying sperm from the epididymis to the urethra. Sperm is then ejaculated out of the penis.

Most men with cystic fibrosis—97 percent to 98 percent—are infertile because of a congenital (bilateral) absence of the vas deferens. The sperm cannot make it to the semen because there is no vas deferens, thus, it can't leave the penis and fertilize an egg.

Although fertility is not directly affected by CF in women, they can have thick vaginal mucus due to abnormal CFTR function, which can make it more challenging for sperm to move into the female reproductive system.

Cystic fibrosis and sexual health

The relationship with sexual health begins early because it's common for adolescents with CF to have delayed puberty. Cystic fibrosis does not affect desire or sexual performance, but the practicalities of the condition can make sex a little more complicated.

People with CF often have symptoms such as persistent coughing, chest pain, coughing up blood or difficulty breathing. This can make sex feel uncomfortable, perhaps painful. It certainly doesn't mean you can't have sex, though. You can adopt techniques such as chest clearance and using bronchodilators prior to sex to help you have a pleasurable experience.


What are the symptoms of cystic fibrosis?

Symptoms of CF usually appear soon after birth. There are many different variants of CF, but the most common symptoms people experience are:

  • Bowel problems such as diarrhea, constipation or large, smelly feces
  • Coughing up thick mucus or blood-stained mucus
  • Infertility in men
  • Jaundice
  • Malnutrition
  • Meconium ileus, or bowel obstruction in newborn babies, is often the first sign of CF
  • Persistent coughing
  • Problems with growth and weight gain
  • Regular lung infections
  • Shortness of breath
  • Wheezing

Other symptoms include osteoporosis (brittle bones), diabetes and liver problems.

How do people get cystic fibrosis?

Cystic fibrosis is a genetic (inherited) condition. A defective CFTR gene is carried by 1 in 25 people. Having one copy of the defective gene does not affect you, so people often don't know they are a carrier. To be born with CF, you must have two faulty CFTR genes, one from each parent. Genetic testing should be considered if you know someone in your family with the condition or for pregnancy planning.

How does cystic fibrosis affect daily life?

Managing CF involves a rigorous routine of airway clearance techniques, medications, exercise and ensuring healthy nutrition. This can take two to three hours each day but is vital to reducing exacerbations and hospital stays. If a person is unwell with an exacerbation, this routine increases as more frequent airway clearance is needed.

Time management can be challenging, especially when you add school, work and home life. But there are teams and apps to help you build a manageable routine.

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An x-ray shows the human lungs glowing orange inside of a blue body.