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Cystic fibrosis - Symptoms of cystic fibrosis

The symptoms of cystic fibrosis can vary in severity from person to person. The thick mucus in the body affects a number of organs, particularly the lungs and digestive system.

Most cases of cystic fibrosis in the UK are now identified through screening tests carried out early in life, before symptoms appear. Read more about screening for cystic fibrosis.

The main symptoms and related problems are detailed below.

Symptoms at birth

Around 10% of babies with cystic fibrosis are born with a serious bowel obstruction, known as meconium ileus. This can make them very ill in their first few days of life.

All babies are born with meconium in their bowels. This is a thick, black substance normally passed out of the body a day or two after the birth.

However, in some babies with cystic fibrosis, the meconium is too thick to be passed through the bowels and causes a blockage. If a baby is born with meconium ileus, an operation to remove the blockage will probably be required.

A few babies will also have symptoms of jaundice (yellowing of the skin, eyes and mucus membrane), which can last for a long time. However, there are many other, more common, causes of jaundice.


It is common for people with cystic fibrosis to experience persistent coughing as the body tries to remove the thick mucus from the lungs. Sudden coughing fits can occur, which sometimes lead to vomiting.

Inflammation in the lungs may cause wheezing, shortness of breath and breathing difficulties, particularly after exercise.


Some people with cystic fibrosis also experience recurring chest and lung infections, which can be severe. These infections are caused by the continual build-up of mucus in the lungs, which provides an ideal breeding ground for bacteria.

The danger is that a person with cystic fibrosis who has such an infection can 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 some 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.

Digestive system

Cystic fibrosis can 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 (malabsorption) and excess fat and protein 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 school-age children and 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 very young children with cystic fibrosis.

Ears, nose and sinuses

People with cystic fibrosis can be prone to sinusitis 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 treated with steroid nose drops or surgically 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.

This 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. However, treatments such as IVF are available. It is important to remember that condoms are still necessary to prevent STIs from spreading.

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 some 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. This can often be treated with pelvic floor exercises.

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.

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