We explain everything about one of the most common genetic diseases.
Today we are talking about cystic fibrosis, a relatively common genetic disease and a high degree of associated mortality , in which those affected secrete a thick mucus that prevents a wide variety of functions, especially respiratory.
What is cystic fibrosis?
Cystic fibrosis is an autosomal recessive genetic disease . This means that the genes it affects are not contained on the sex chromosomes, and that the disease will only occur if the child inherits two mutant copies from their parents, leaving them without a functional gene that can avoid the effects of the mutation.
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This mutation occurs in a large gene on chromosome 7, called CFRT . This gene codes for a protein involved in the transmembrane transport of chloride in cells. Its functions are directly related to the production of sweat, some digestive fluids and other secretions . When this protein does not work properly, related functions are affected, leading to the symptoms of cystic fibrosis.
The mutation that produces the disease is not always the same. There are more than 1,600 CFRT mutations capable of causing cystic fibrosis. Even so, more than 70% of cystic fibrosis cases are caused by a specific mutation, known as ΔF508. This name indicates a loss of an amino acid (phenylalanine) at position number 508 of the CFRT gene, which prevents the normal function of the protein.
Symptoms
Cystic fibrosis is often imagined as a solely respiratory disease. Although it is one of the functions most affected by the disease, this disease causes different symptoms in various parts of the body where the CFRT gene protein is necessary for the proper functioning of the tissue.
Those affected by cystic fibrosis secrete much thicker mucus than usual . This affects many different physiological systems, as this thick mucus blocks various narrow passageways in the body, such as some in the endocrine or reproductive system, causing the different symptoms of the disease.
People with cystic fibrosis present symptoms at various levels, both respiratory and endocrine, gastrointestinal and in the reproductive system. Below we will explain some of its symptoms and later the causes of these health problems in greater depth.
It should be noted that this disease evolves with age, worsening over time and accumulating symptoms as those affected grow. Due to this, they currently have an average life expectancy close to 40 years .
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1. Respiratory symptoms
At the respiratory level is where this disease is most dangerous. Cystic fibrosis patients secrete a dense mucus that hinders respiratory action, in addition to greatly facilitating the appearance of chronic respiratory infections.
These chronic infections, added to the direct effects of mucous secretions, end up causing serious structural changes to the lungs , which will function worse and worse, being prone to other respiratory diseases that are added to cystic fibrosis. The complicated respiratory condition of these patients can also lead to cardiovascular diseases.
At the nasal level, this mucous secretion is also produced, which can cause the patient to develop nasal polyps, which further obstruct the airways and can cause pain.
The respiratory symptoms of cystic fibrosis account for approximately 95% of the mortality associated with this disease . This is why it is usually known as a respiratory disorder, but its patients unfortunately have other symptoms.
2. Gastrointestinal, hepatic and pancreatic symptoms
At the gastrointestinal level, cystic fibrosis also causes blockages and obstructions. In fact, one of the ways of diagnosing cystic fibrosis before the existence of more modern tests, was that the newborn affected by cystic fibrosis was usually not able to pass their first stool.
Those affected by cystic fibrosis also have an increased risk of suffering from anal prolapse and serious problems with the absorption of nutrients . These symptoms are due to the fact that the pancreas is affected by mucous secretions, and its necessary pancreatic enzymes for digestion do not reach the intestine correctly.
The pancreas can be affected more directly, causing a loss in the cell population that produces insulin, which can lead to diabetes . The liver in turn could develop cirrhosis due to the damage caused by the obstruction of the bile ducts.
3. Reproductive symptoms
This is a problem mainly in men. The mucous secretion of those affected by cystic fibrosis can also prevent the passage of sperm to the rest of the semen components, leaving these individuals virtually infertile unless reproductive surgery is applied to extract their sperm directly from the gonads.
This impediment to the passage of sperm occurs in approximately 99% of men affected by cystic fibrosis .
4. Other symptoms
There are also a multitude of different symptoms associated with cystic fibrosis. These include developmental problems, osteoporosis, or abnormally salty skin due to an ionic imbalance in the body.
The symptoms of cystic fibrosis are not the same for all patients . Although some are almost universal, their severity can vary depending on the type of mutation they present, since a higher degree of functional CFRT causes fewer symptoms.
Current Treatment
Cystic fibrosis affects approximately 1 in 4,000 people annually in Europe. Currently, the average life expectancy of these patients is less than 40 years. Even so, experts estimate that those affected by cystic fibrosis born in the 21st century will exceed 50 years of life.
Although the disease currently has no cure, we are much better informed about how to treat the various symptoms of this disease as they appear, while taking steps to prevent them.
Different types of symptom-specific medication, such as antibiotics, are used to treat respiratory infections . Lung transplants are performed for those patients who need it, but these are measures that, although welcome, do not serve to cure the disease.
Gene therapy is of particular interest in cystic fibrosis, because the disease appears to be primarily monogenetic in origin (only one gene is the culprit). Despite this, the large number of affected cells in different systems currently means that gene therapy is not feasible to cure cystic fibrosis patients .
Bibliographic references
- Davies, JC, Alton, EW, & Bush, A. (2007). Cystic fibrosis. BMJ (Clinical research ed.), 335(7632), 1255–1259. doi:10.1136/bmj.39391.713229.AD
- Naehrig, S., Chao, CM, & Naehrlich, L. (2017). Cystic Fibrosis. Deutsches Arzteblatt international, 114(33-34), 564–574. doi:10.3238/arztebl.2017.0564.
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