Cystic Fibrosis – Genetic testing for Cystic Fibrosis (CF)

Cystic Fibrosis (also known as CF) is a hereditary genetic disease that causes damage to the lungs and digestive system.

Genetic and pathological basis of cystic fibrosis

Cystic fibrosis is caused by a fault in the gene responsible for protein coding in the ion channels in the body. These channels move chloride from the cells. Faulty genes can cause these channels to function incorrectly, which can result in various health conditions.

The gene linked to cystic fibrosis is called CFTR and is located on chromosome 7. Cystic fibrosis is an autosomal recessive disease, which means that both parents can pass down a faulty gene to their child. Carrier parents’ chances of having a baby with CF are 25%.

The severity of the disease depends on the protein mutation. Certain mutations reflect in a wide set of severe symptoms, whereas others reflect only in infertility. The most common mutation is delta F508, but there are over 1000 known mutations.


Children with cystic fibrosis suffer from failure to thrive and recurring infections in their respiratory system. The disease causes an accumulation of thick mucus in the airways, this mucus can also trap germs leading to infections, that can be life threatening. 

Further complications of CF include bronchiectasis (an irregular widening of the airways), nasal polyps, frequent sinus infections (sinusitis), and more.

Other organs affected by cystic fibrosis are the pancreas (in charge of producing digestive enzymes), and the sweat glands.

Digestive system complications include bowel obstructions, rectal prolapse, cirrhosis, fat-soluble vitamin deficiencies (vitamins A, E, D and K), and more. Newborns with CF may also suffer from Meconium ileus (bowl obstruction) and volvulus (a twisting of the bowel around itself).

In addition, males with CF suffer from infertility, due to defects in the function of the sperm canal.


When a suspicion for cystic fibrosis arises (such as a delay in growth combined with recurring respiratory diseases, or a family history of CF), there are several tests that can help get a diagnosis.

A sweat test can identify the high levels of chloride in the sweat and is considered a diagnostic criterion. Test results of over 60 mmol\L if chloride in the sweat is an almost certain indication of CF, while a result of 40 and above means that CF is possible. Another (less useful) test is NPD, or nasal potential difference test.

Today, modern molecular testing technologies can also assist CF diagnosis. When there is a known mutation for CF in the family, it can be identified using a PCR test. However, in many cases the mutation in the gene causing the disease is unknown, which poses a difficulty in performing and interpreting PCR tests (there are many known cystic fibrosis mutations). Getting a diagnosis in this way is only possible after an absolute identification of a mutation in a gene responsible for CF (such as delta F508).


Unfortunately, there is no known cure for cystic fibrosis today. CF is a chronic condition that will affect patients throughout their entire lives. However, there have been significant developments in supporting treatment of CF, that has enabled an improvement in the quality of life of people with CF.

Treatments include antibiotics for treating lung infections, enzyme supplements for those with pancreatic damage, physiotherapy that helps drain liquid and mucus from the lungs, and mucus-thinning drugs. Due to improvements in available treatments today, patients that follow treatment can live longer and healthier lives.


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