WHAT IS CYSTIC FIBROSIS
Cystic fibrosis (CF) is one of the most common genetic disorders1. It is a life-threatening disease that affects mainly respiration, digestion and reproduction. CF is currently incurable, however, there is ongoing research all over the world focused on finding a cure (see Treatment Options).
CF mostly affects people with Northern European ancestry2. 1 in every 2000-3000 children born in the European Union is affected by CF. In the United States of America, it is 1 in every 3500 births. In Asian and African populations, the occurrence of CF is rare1. However, in developing countries with poor healthcare systems children with CF often die before being diagnosed.
CF is caused by mutations in the CFTR gene (see The Role of Genetics), which results in a defective CFTR protein. A functional CFTR protein is a channel that transports ions, specifically chloride and bicarbonate, to the cell surface. Defective CFTR proteins cannot help transport these ions, which ultimately causes abnormally thick and sticky mucus in multiple organs3.
Which Organs Are Affected?
The thick, sticky mucus typical for CF negatively impacts the lungs, pancreas, liver, and both male and female reproductive organs.
In the lungs, this mucus creates an ideal environment for infections caused by viruses and bacteria, such as Haemophilus influenzae, Staphylococcus aureus, Pseudomonas aeruginosa and Burkholderia cepacia2. Some bacteria, like Mycobacterium abscessus, are becoming more widespread in patients with CF, as they are resistant to antibiotics and consequently difficult to treat4,5. Frequent respiratory infections lead to damage caused by inflammation. Currently, progressive lung disease and respiratory failure are the most common cause of death in people with CF2.
Defective CFTR protein also affects the pancreas and liver6. In the pancreas, the buildup of mucus prevents the release of digestive enzymes, which leads to pancreatic insufficiency. As the nutrients cannot be properly absorbed, people with CF suffer from malnutrition and poor growth. The mucus in the liver blocks the bile ducts, which prevents the release of bile and causes liver disease. Pancreatic disease ultimately leads to diabetes mellitus, which contributes towards lower chances of survival7.
CF-related mucus affects fertility in both men and women. Whilst the vast majority of men with CF are infertile (though able to have biological children with assisted reproductive techniques), women are less affected in comparison8,9.
What Are the Symptoms of Cystic Fibrosis?
The symptoms of CF vary from person to person, partly based on the specific mutation in the CFTR gene. The most common symptoms of CF include10:
- Salty-tasting skin
- Persistent coughing, sometimes with phlegm
- Frequent lung infections including pneumonia or bronchitis
- Wheezing or shortness of breath
- Poor growth and weight gain despite a healthy diet
- Greasy, bulky stools or difficulty with bowel movements
- Male infertility
How Is Cystic Fibrosis Diagnosed?
Early diagnosis and treatment of CF can help delay or even prevent some serious health issues connected with CF. Most countries with a high prevalence of CF have implemented newborn screening11. Usually, blood samples are collected from babies by a heel prick soon after birth and then used, among other things, for immunoreactive trypsinogen testing. The level of immunoreactive trypsinogen is higher in babies with CF, but it can be also due to a premature or stressful delivery12. That is why this initial test is ideally followed by DNA testing for a panel of common CF mutations. A sweat test measuring how much salt is in the baby's sweat is done as the final diagnostic test13.
This is how most children with CF are diagnosed across multiple countries including the United States, United Kingdom, Australia and many European countries14. The diagnosis of CF comes as a surprise to most parents as more than 95 % have no family history of CF14. This is due to the fact that among the Caucasian population, 1 person in 25 is a carrier of CF without being affected themselves (see The Role of Genetics).
Some people are diagnosed with CF as adults. They usually have a mutation associated with a partially functional CFTR protein (see The Role of Genetics) and have only milder symptoms in childhood. Once in adulthood, they can also develop bronchiectasis, pancreatitis or infertility. They generally have good rates of survival2.
- 1 - https://www.who.int/genomics/public/geneticdiseases/en/index2.html
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- 9 - T. J. McCallum, J. M. Milunsky, D. L. Cunningham, D. H. Harris, T. A. Maher, and R. D. Oates, “Fertility in men with cystic fibrosis: An update on current surgical practices and outcomes,” Chest, vol. 118, no. 4, pp. 1059–1062, 2000.
- 10 - https://www.cff.org/What-is-CF/About-Cystic-Fibrosis/
- 11 - S. J. Mayell et al., “A European consensus for the evaluation and management of infants with an equivocal diagnosis following newborn screening for cystic fibrosis.,” J. Cyst. Fibros., vol. 8, no. 1, pp. 71–8, Jan. 2009.
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