Cystic fibrosis (CF) is an inherited condition. It can have many symptoms, affecting different parts of the body, particularly the lungs and digestive system. CF is the most common inherited disease in white people, affecting about 1 in every 2,500 children born. It is much rarer in people of African or Asian descent. About one in five babies with CF are diagnosed at birth, when their GI tract becomes blocked by extra thick meconium (the black tar-like bowel contents that all babies pass soon after birth). This condition may require surgery.

Just over half of people with CF are diagnosed as babies because they are not growing or putting on weight as they should. This is because the pancreas is not producing enzymes which pass into the gut as food leaves the stomach. Without these enzymes, the fat in food cannot be properly digested. In children who are affected, the fat passes straight through the gut. The child does not benefit from the energy from the fat. Since the stools contain an excess of fat, they are oily and very smelly.

CF is a "multi-system" disease, meaning that it affects many body organs. However, most of the symptoms have to do with the lungs and the GI tract.

In a healthy person, there is a constant flow of mucus over the surfaces of the air passages in the lungs. This removes debris and bacteria. In someone with CF, this mucus is excessively sticky and cannot perform this role properly. This mucus provides an ideal environment for bacterial growth and subsequent infection.

People with CF are at risk of bacterial chest infections. About half of people with CF have repeated chest infections and pneumonia. If they are not treated early and properly, these are very difficult to treat. Symptoms include persistent coughing, excess production of sputum (saliva and mucus), wheezing, and shortness of breath with ordinary activities.

If people with CF do not have proper treatment, they will continue to have oily bowel movements, abdominal pain, and problems putting on weight. Constipation is also a frequent symptom. Occasionally the gut becomes completely blocked, resulting in extreme stomach pain.

In each cell in our bodies we have 22 pairs of chromosomes and one pair of sex chromosomes. These contain the genes that help to determine how cells grow and function.

The abnormal gene that causes CF is found on chromosome number 7. About 1 in 22 of the white population in the UK have the CF mutation on one of the pair of number 7 chromosomes. These people are called "carriers" of the CF gene. They have no symptoms of CF – this happens only when there are CF mutations on both number 7 chromosomes (see diagram). When both parents are carriers, there is a one in four chance of having a child with CF, a one in two chance of having a child who is a carrier and a one in four chance of having an unaffected child.

There are several different types of genetic mutation which are associated with different degrees of severity of the disease.

Although there is currently no cure for CF, there is a lot of research under way to try to find a cure for CF lung disease through gene therapy.

Children born with CF do not have a normal life expectancy, though it is improving all the time. The average survival is now more than 30 years, but with the best treatment, children today with CF have a greater than 80% chance of living into their late forties.

If someone has a family history of CF, they can be tested to see if they carry the CF gene before they have a family. If a couple are both carriers or if they already have a child with CF, tests can be done early in pregnancy to see if the fetus is affected. This is called chorionic villus sampling and involves taking a biopsy (a sample of tissue) from the placenta. However, there is a small risk a miscarriage with this test. Also, if the biopsy produces a positive result for CF, the parents then face a difficult decision of whether or not to continue with the pregnancy.

Routine newborn (neonatal) screening for CF has recently received government approval in some countries. It is done using the same blood sample that is already taken from the baby six days after birth to test for two other conditions, low thyroid function and phenylketonuria.

Causes of idiopathic or primary clubbing include the following:

• Pachydermoperiostosis
• Familial clubbing
• Hypertrophic osteoarthropathy

Causes of secondary clubbing include the following:

• Pulmonary disease - Lung cancer, cystic fibrosis, interstitial lung disease, idiopathic pulmonary fibrosis, sarcoidosis, lipoid pneumonia, empyema, pleural mesothelioma, pulmonary artery sarcoma, cryptogenic fibrosing alveolitis, and pulmonary metastases
• Cardiac disease - Cyanotic congenital heart disease, other causes of right-to-left shunting, and bacterial endocarditis
• Gastrointestinal disease - Ulcerative colitis, Crohn disease, primary biliary cirrhosis, cirrhosis of the liver, leiomyoma of the esophagus, achalasia, and peptic ulceration of the esophagus
• Skin disease - Pachydermoperiostosis, Bureau-Barrière-Thomas syndrome, Fischer syndrome, palmoplantar keratoderma, and Volavsek syndrome
• Malignancies - Thyroid cancer, thymus cancer, Hodgkin disease, and disseminated chronic myeloid leukemia
• Miscellaneous conditions - Acromegaly, thyroid acropachy, and pregnancy

People with CF need daily chest physiotherapy, which involves vigorous massage to help loosen the sticky mucus. Parents of a child with CF are taught by hospital staff how to do this. Older children and adults with CF can be taught to do this for themselves.

People with CF also need to have any chest infection treated quickly with antibiotics. The usual childhood vaccinations, such as MMR (measles, mumps and rubella) and DTP (diptheria, tetanus and whooping cough) are important for people with CF, and they should also be vaccinated against flu and pneumococcus to help prevent chest infections.

With each meal or snack, most people with CF need to take capsules that supply the missing pancreatic enzymes and allow proper digestion.

There is a range of other possible treatments, according to each person’s condition. These may include:

• daily oral or inhaled antibiotics to counter lung infection
• inhaled anti-asthma therapy, corticosteroid tablets
• dietary vitamin supplements, especially A and D
• inhalation of a medication called pulmozyme to make the sputum less sticky
• medicines to relieve constipation or to improve the activity of the enzyme supplements
• insulin for CF-related diabetes
• medication for CF-associated liver disease
• oxygen to help with breathing
• in severe cases, a lung or heart and lung transplant operation
• help to overcome fertility problems
• counseling to help cope with the psychological aspects.