Cystic fibrosis (CF) is a chronic disease that affects the secretory glands, which are responsible for producing mucus and sweat. Patients with cystic fibrosis overproduce mucus, causing malfunction in the lungs, pancreas, liver, intestines, sinuses, and sex organs. In healthy people, mucus is a watery and slippery substance that keeps the organs moist and prevents dehydration and infections. However, in CF patients, it is sticky and thick.
The mucus ends up accumulating in the lungs and airways, causing a blockage and preventing patients from properly breathing, as well as promoting the growth of bacteria and the development of infections. Other symptoms of cystic fibrosis include persistent coughing, wheezing, an intolerance to exercise, inflamed nasal passages or a stuffy nose, foul-smelling and greasy stools, poor weight gain and growth, intestinal blockage, particularly in newborns (meconium ileus), and severe constipation.
How Genetics Cause Cystic Fibrosis
Cystic fibrosis is known to be an inherited disease related to a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The CFTR gene is responsible for the production of a protein that controls salt and water movements in the cells. Due to this defect, the protein does not work properly in CF patients, provoking the production of thick, sticky mucus and very salty sweat. Cystic fibrosis patients inherit one CFTR gene from each parent; those who have just one faulty CFTR gene are known as carriers of the disease. These people usually don’t have symptoms, but can pass the disease on to their children.
When a child inherits two faulty CFTR genes — one from each parent — he or she will develop the disease. Even though the cause for cystic fibrosis is known, there are over 1,000 defects that can affect the CFTR gene. These defects impact the severity of the disease. The total number of defects is still unknown. Other genes also impact the severity of cystic fibrosis. As a result, the diagnosis and treatment of the disease is difficult. There is currently no cure. Research demonstrates that the CFTR protein may affect other parts of the body, which can explain additional CF symptoms and complications.
Risk Factors that Contribute to the Genetic Cause of Cystic Fibrosis
Anyone can suffer from cystic fibrosis, regardless of gender or ethnic group, as long as they have the faulty CFTR gene. It is estimated that more than 10 million people carry a faulty CFTR gene in the U.S. alone according to the National Institutes of Health (NIH). In the United States, about 30,000 people live with cystic fibrosis, and 70,000 worldwide. Even though the disease does not discriminate, there are two factors strongly linked to the disease: family history and race. It is most common among Caucasians of Northern European descent, Latinos, and Native Americans, especially the Pueblo and Zuni.
The authors of the study “Clinical and genetic risk factors for cystic fibrosis-related liver disease” focused on possible risk factors for the development of cystic fibrosis and revealed that “of the 288 patients screened, 80 (28 percent) had liver disease. Of the 256 patients with pancreatic insufficiency, 80 (31 percent) had liver disease compared with none of the 32 patients with pancreatic sufficiency. Genotype-phenotype correlation was performed on 207 patients carrying identified mutations that were previously classified according to phenotype severity. Liver disease was found in 56 (32 percent) of 173 patients carrying mutations associated with a severe phenotype and in six (38 percent) of 16 patients carrying at least one mutation associated with a variable genotype (G85E and/or 5T allele). In conclusion, “CF patients who have pancreatic insufficiency and carry mutations associated with a severe or a variable genotype are at increased risk to develop liver disease.”
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