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Cystic fibrosis - Symptoms of cystic fibrosis

NHS Choices Medical Reference

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When a child is born with cystic fibrosis, symptoms usually appear in the first year, although occasionally they develop later.

The thick sticky mucus in the body affects a number of organs, particularly the lungs and digestive system.

The symptoms and related problems of cystic fibrosis can vary in severity from person to person.

The main symptoms and problems are detailed below.


It is common for people with cystic fibrosis to have difficulties such as:

  • persistent coughing and wheezing; the body tries to shift the thick mucus in the lungs by coughing it up
  • recurring chest and lung infections; infections are caused by the continual build-up of mucus in the lungs, which provides an ideal breeding ground for bacteria


People with cystic fibrosis are vulnerable to harmful lung infections caused by certain strains of bacteria (these bacteria are rarely harmful to people without cystic fibrosis).

Two strains of bacteria that commonly infect people with cystic fibrosis are Pseudomonas aeruginosa and Staphlyococcus aureus. They multiply in the thick mucus inside the lungs and may cause serious health problems, such as repeated chest infections.

The danger is that a person with cystic fibrosis who has such an infection can easily pass it on to another person with cystic fibrosis through close personal contact or by coughing near them. This is known as cross-infection.

As more and more people with cystic fibrosis become infected with these bacteria, the bacteria may become resistant to antibiotic treatment, which is why cross-infection is such a problem.

There is a concern that people with cystic fibrosis are more likely to pick up strains from each other than from the environment. For this reason, it is recommended that people with cystic fibrosis do not come into close contact with each other.

Patients infected with these dangerous bacteria may be treated in separate clinics to those without the bacteria, to avoid cross-infection.

You can get more advice on cross-infection from the Cystic Fibrosis Trust website.

Digestive system

Cystic fibrosis can also cause mucus to block the ducts in the pancreas. The pancreas produces essential food-digesting enzymes. When it is blocked, not enough of the enzymes reach the intestines to help break down food, which can cause a number of troublesome symptoms. These are outlined below.

Large, smelly stools

If the digestive enzymes are not being produced, food is not adequately digested and excess fat is lost in the stools ('poo'), making them bulky, oily, smelly and difficult to flush away.


Because the body cannot digest essential nutrients in food (particularly fat), it is often difficult to gain weight and infants may struggle to put on weight and grow. The medical term for not consuming sufficient nutrients is malnutrition.

Adults with cystic fibrosis often find it difficult to gain and maintain weight. In children with cystic fibrosis, this can result in delayed puberty if they are severely underweight.


In older people with cystic fibrosis, the pancreas can become more damaged. Diabetes can develop if the pancreas does not produce enough insulin, a hormone that controls the level of sugar in the blood.

Diabetes in people with cystic fibrosis is different from diabetes in people without cystic fibrosis. Usually, the symptoms of diabetes include feeling constantly thirsty, frequently needing to pass urine and feeling extremely tired.

This is less common in people with cystic fibrosis. Instead people with cystic fibrosis who develop diabetes may find it difficult to gain weight or may lose weight and see a decline in their lung function.

Cystic fibrosis-related diabetes is usually controlled by regular injections of insulin. Diabetes rarely occurs in children with cystic fibrosis.

Ears, nose and sinuses

People with cystic fibrosis can be prone to sinusitis (an infection of the cavities behind the cheekbones), which may need to be treated with nasal sprays or antibiotics.

Some older children and adults develop nasal polyps, which are fleshy swellings that grow from the lining of the nose or sinuses. If they become troublesome, they may need to be removed.

Bones and joints

Some older children with cystic fibrosis develop a form of arthritis (swelling and pain of the joints), usually in one or two large joints such as the knee. In most cases, symptoms improve with time and treatment.

Older children and adults may also be prone to thin bones, for many reasons, including repeated infection, poor growth or weight, lack of physical activity and lack of vitamins and minerals due to digestive problems.

People with cystic fibrosis are more at risk of developing osteoporosis if they are taking steroid medication (corticosteroids) to help with lung infections. Osteoporosis can cause joint pain and bones may fracture (break) more easily. Some people need to take drugs called bisphosphonates to help maintain their bone density.


Both men and women with cystic fibrosis can have problems conceiving children.

In virtually all men with cystic fibrosis, the tubes that carry sperm do not develop correctly, making them infertile.

Women with cystic fibrosis may find that their menstrual cycle becomes absent or irregular if they are underweight.

There is also an increased thickness of cervical mucus, which can sometimes reduce fertility.

However, some women with cystic fibrosis can have a successful pregnancy, though it may take longer than usual before conceiving a baby.


In a few people with cystic fibrosis, the tiny bile ducts in the liver can become blocked by mucus. This can be serious as the disease progresses, and in some cases it may be necessary to have a liver transplant.


People with cystic fibrosis, especially females, are more likely to have urinary incontinence (loss of bladder control) as urine can leak out of the bladder during coughing fits.  

Enzymes are proteins that speed up and control chemical reactions, such as digestion, in the body.
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.
Stool (also known as faeces) is the solid waste matter that is passed from the body as a bowel movement.
Medical Review: March 22, 2012
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