What is Cystic Fibrosis? - CF Buzz

What is cystic fibrosis?

Cystic Fibrosis (CF) is an inherited genetic condition. It’s the most common genetic disease in Australia and large parts of the rest of the world. Every 4 days a baby is born with CF and around 1 in every 25 people in Australia are carries of a CF gene, most of the time, CF carriers don’t even know that they have a CF gene.

CF is what is known as an Autosomal Recessive Disorder, this means that it’s an inherited condition, and you can carry a copy of a CF gene without having any symptoms. For a person to be born with CF, they must inherit a CF gene from both their mother and their father. For more detailed information about autosomal recessive inheritance, take a look at the  NSW Health fact sheet.

 

How does it happen?

At conception, a baby inherits two sets of chromosomes, one from the mother and one from the father. These chromosomes contain all the genetic information for the baby to grow and develop. If both parents are carriers of a CF gene, there is a 1 in 4 chance that any baby born could have CF. If both parents pass on a CF gene, the baby will have Cystic Fibrosis.

CF-Inheritance-Diagram-2

 

What does the cystic fibrosis gene do?

The CF gene, called CFTR ( Cystic Fibrosis Transmembrane Conductance Regulator) gene controls the way water and salt (sodium), move across the body cells (called epithelial cells) that line our respiratory system, digestive system and reproductive systems. In a person with CF, the CFTR gene is faulty. When the CFTR protein is faulty, epithelial cells can’t regulate the way that chloride (part of the salt called sodium chloride) passes across cell membranes. This disrupts the essential balance of salt and water needed to maintain a normal thin coating of fluid and mucus inside the lungs, pancreas, and passageways in other organs.

The result is thick sticky mucous which plugs up small airways, parts of the gut, and the small ducts between the pancreas and the intestine. The mucous can also affect the reproductive system. Because of the difficulty the body has in getting sodium and water into body cells, a person with CF will have higher levels of salt in their sweat, and can dehydrate easily.

 

How is cystic fibrosis diagnosed?

 

Heel prick test

All newborns in Australia have the opportunity to undergo newborn screening to test for the risk of rare, but serious, medical conditions including phenylketonuria, hypothyroidism and cystic fibrosis.Usually called the heel prick test, it’s also known as the Guthrie test or blood spot testing. A small amount of blood is taken from the baby’s heel and sent for analysis.However, the heel prick test doesn’t pick up all cases of cystic fibrosis.

 

Heel Prick Test

 

Sweat test

The sweat test is used as the definitive test for cystic fibrosis.A sample of sweat is analysed for chloride concentration levels, and sometimes sodium concentration levels; high levels of chloride in sweat is extremely common in people with CF.

This test is usually carried out when a baby is at least two weeks old and often because they have other symptoms like bowel blockages and/or frequent chest infections. Sweat tests will be used if both parents are known to be carriers of mutated CFTR genes.

You can check out CF Australia’s fact sheet on the sweat test here.

 

How is cystic fibrosis treated?

As there are so many different types of cystic fibrosis, all with a variety of symptoms, there’s no typical treatment plan.

People with CF need to work closely with their health team to work out a personalised treatment plan, which will include a combination of the following:

  • Airway clearance to help clear the thick mucus that can build up in the lungs. There are a few different methods, one is manual physiotherapy performed by someone else, another is the use of an inflatable vest that vibrates the chest
  • Inhaled medicines to open the airways and thin out the mucus. These are liquid medications inhaled through a nebuliser that include antibiotics
  • Enzyme supplements to help the digestion of food, taken with every meal and most snacks.
  • Salt and vitamin supplements are often taken as well
  • A high calorie diet, high in salt and fat is needed as people with CF don’t absorb salt and also find it hard to put on weight
  • Exercise to keep the lungs and the rest of the body strong and functioning as well as possible

 

Carrier screening

Screening to find out if you are a carrier of a mutated cystic fibrosis Transmembrane Conductance Regulator gene is fairly easy. All you need to do is provide a blood or saliva sample.

As there are over 1800 known mutations, testing is usually narrowed down to the most common forms in Australia, unless you can provide a specific family history.

Some of the mutations are particular to individual families, but on the other end of the scale, the Delta F508 mutation is present in 72 per cent of all cases of CF worldwide.

For more information on cystic fibrosis screening, visit www.cfscreening.com.au.

Click here for download a brochure on information about screening for CF.



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