Cystic Fibrosis Questions

By Dr Ananya Mandal, MD

Some of the frequently asked questions regarding cystic fibrosis include:

What is cystic fibrosis?
Cystic fibrosis is a genetic condition that affects the production and flow of mucus within the respiratory system and digestive system. As a result, the passageways in these areas become clogged with a thick, sticky mucus, which leads to symptoms of the condition such as persistent coughing and failure to thrive.

What is newborn screening for cystic fibrosis?
All newborn babies are screened for cystic fibrosis. A small amount of the baby’s blood is taken by heel prick and transferred to a special card which is sent for laboratory analysis. This blood is tested for levels of immunoreactive trypsinogen. This is a pancreatic enzyme precursor that is elevated in cystic fibrosis due to blocked pancreatic ducts failing to drain adequately. The earlier the condition is detected, the sooner treatment can be started.

How can cystic fibrosis be confirmed after an abnormal cystic fibrosis screen?
If cystic fibrosis is suspected, genetic testing is performed to look for the mutation that causes the disease. The mutation occurs in the gene that codes for a protein called the cystic fibrosis transmembrane conductance regulator (CFTR). This test may be used to confirm whether the child has a CFTR mutation and also to establish the carrier status of family members.

When can a sweat test be performed in a baby?
If the genetic testing or newborn screening suggests an infant may have cystic fibrosis, the diagnosis is confirmed using a sweat test, which measures the amount of chloride present in a patient’s sweat. For collection of the sweat, a chemical that causes sweating is placed on a small area of the arm or leg and an electrode is placed over the area. A weak electrical current is then applied, which causes sweating and a mild tingling, warm sensation. After five minutes, the current is stopped and the electrode removed. The sweat is collected on a piece of filter paper or gauze and sent for analysis. High levels of chloride in the sweat indicates cystic fibrosis.

What are the symptoms of cystic fibrosis?
Symptoms usually manifests within the first year of life and include a persistent cough, recurrent chest infections and excessively salty sweat. When pancreatic ducts are affected, there is a reduction in the secretion of digestive enzymes. This disrupts the breakdown and absorption of food in the intestine which affects the infant’s ability to gain weight and develop at the expected rate.

What is the treatment for cystic fibrosis?
Cystic fibrosis is an incurable genetic condition and treatment is aimed at easing symptoms as much as possible as well as preventing or reducing the long-term damage that can be caused by infections and other complications. For example, bronchodilators are used to help expand the airways of the lungs and make it easier to breathe, while antibiotics are used to combat infections. Routine vaccinations protect against life-threatening infections. Another important part of treatment is physiotherapy, which involves a range of exercises the can help clear mucus from the airways of the lungs.

How can cystic fibrosis occur?
In cystic fibrosis, mutation of the CFTR gene leads to the formation of a cell transmembrane protein that lets too much salt and not enough water into the cells. This causes the build up of the thick and sticky mucus that clogs the lungs and respiratory system. A person needs to inherit two copies of the defective CFTR gene in order to develop cystic fibrosis.

Everyone inherits two CFTR genes, one from the mother and one from the father. When a person inherits one abnormal copy of the CFTR gene, they are termed a carrier. If that person has a baby with another carrier, there is a one-in-four chance that their offspring will not inherit either of the faulty genes. However, there is a one-in-two chance the child will inherit one faulty gene and be a carrier of the condition and a one-in-four chance they will inherit both the mutated genes and develop the condition.

Reviewed by , BSc

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Last Updated: Apr 14, 2014

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