Cystic fibrosis also called CF is a hereditary disease caused by gene mutations. The National Heart and Lung Institute (NHLI) states that the disease affects organs like reproductive organs, liver, lungs, sinuses, pancreas and the intestines (2009). The disease causes the secretory glands to excrete excessive mucus. The mucus lines some tissues in the body. Typically, the mucus is “a slippery, watery substance” that helps to keep the organs moist and prevent them from being infected or drying out (NHLI, 2009, para. 2).
However, CF causes the mucus to become sticky and thick and blocks passages in the lungs and the pancreas eventually leading to diseases because the mucus forms a breeding ground for bacteria. The disease has a high prevalence among people of Caucasian descent from Europe, Australasia and North America. Nonetheless, CF is found in other populations for instance in the Middle East and Latin America, blacks have the lowest prevalence rates (Savopoulos & Oversteegen, 2006).
People suffering from CF exhibit different types of symptoms. The respiratory system symptoms include very salty sweat, difficulty in breathing due to blocked airways, which also cause frequent coughs that contain thick sputum, and at times, it contains blood, infections that fail to respond to local antibiotics, sinusitis, pneumonia, bronchiectasis, some patients grow nasal growths. Digestive system symptoms include, foul-smelling greasy stools, constipation, diarrhea, excessive gas, poor growth in children and in young children blockage of the intestines may occur.
Children also have stunted growth because enzymes that help in nutrient absorption are blocked and thus do not function properly. In severe cases liver disease, diabetes, gallstones and pancreatitis. Reproductive system symptoms are infertility in men as they are born minus the vas deferens. Women conceive with difficulty due to blocked fallopian tubes. Other symptoms are dehydration, tiredness, heart stroke, weakness, clubbing of tips of the fingers and toes due to lack of sufficient oxygen in the bloodstream and osteoporosis (NHLI, 2009).
CF is caused by a gene mutation. The gene that mutates is found on chromosome 7 and it is Cystic Fibrosis Transmembrane Regular (CFTR). It produces the “protein that helps to control the movement of chloride and bicarbonate in and out of cells” (Keyes, Lassiter & Roberts, 2006, p. 1). CFTR is responsible for creating a pore in the cell membranes to create room for the passage of elements. The pore can either restrict or allow elements to pass.
However, in a person with CF, the cell pores are blocked and thus chloride and other important ions are not released and this leads to salt imbalance. The imbalance leads to the release of thick mucus that accumulates in the lungs. The CFTR gene can discriminate and block the passage of either sodium or chloride. The degree to which the defective CFTR gene blocks the flow of sodium and chloride determines the severity of the CF (Keyes, Lassiter & Roberts, 2006; Rosaler, 2007).
The mechanism underlying the abnormality in the sweat gland is the improper functioning of ion transport. Secretion occurs in the granular coil which “is modified as it traverses the sweat duct” before being released on the surface of the skin (Quinton, 2007). In a person without CF, the sodium and chloride ions in that order are reabsorbed from the ductular lumen via CFTR and apical sodium channels. However, in a patient with CF the improper functioning of CFTR inhibits the reabsorption of the ions thus, the amount of salts that get absorbed is poor (Quinton, 2007). Consequently, a patient’s sweat contains a high concentration of salt (Rowe, Miller & Sorscher, 2005).
The mode of inheritance of CF takes place through the defective CFTR gene. The gene is responsible for making a protein that regulates the intake of water and salt in and out of body cells. People suffering from CF have a protein that malfunctions causing the release of sticky thick mucus and salty sweat (NHLI, 2009). People suffering from CF inherit it from their parents because each child inherits a pair of CFTR genes from the mother and father.
Children who inherit a defective CFTR from both parents suffer from CF. In this case, both parents are carriers of the CF recessive gene. In case a child inherits only one defective CFTR gene from one parent and a normal CFTR from the other, they become carriers as seen on the figure below. Carriers lead normal lives and do not suffer from any symptoms associated with CF but can pass the defective gene to their offspring (NHLI, 2009).
The mutations in CFTR happen due to the presence of nonsense alleles. X indicates the nonsense alleles and this type of mutation occurs in about 5 to 10% of CFTR mutations. It is important to note that there are many types of CFTR mutations. The X-linked recessive genes are passed down by parents to their children. Another type of mutation is G551D or class three that contains insignificant or no chloride channel hence the CFTR cannot allow the absorption of chloride ions. The other is the A455E mutation that has a partial ion channel function (Rowe, Miller & Sorscher, 2005).
The disease has no known cure yet but treatments have been developed. The first step is infection prevention because the diseases can be passed from one person to another. They are various types of CF causing pathogens some deadly than others and in all types segregation of the infected persons is important. Washing hands properly also prevents infections as well as proper sterilization of health equipment in hospitals. The environment is also decontaminated to prevent the spread of germs (O’Malley, 2009).
Other treatments involve the use of antibiotics to fight the bacteria that cause lung infections by keeping the airways clear but prolonged use can lead to the development of drug-resistant bacteria. Mucus thinning drugs are also used to loosen the thick sticky mucus in the airways. Oral enzymes, bronchodilators, bronchial airway drainage, improved nutrition, gene therapy and in chronic cases lung transplant (Keyes, Lassiter & Roberts, 2006). The treatments have raised the life expectancy of CF patients.
References
Keyes, D, Lassiter, A & Roberts, GH. 2006. ‘Cystic Fibrosis.’ Journal of Continuing Education Topics & Issues, Vol. 8, No. 1, pp. 10-15.
National Heart and Lung Institute. Cystic fibrosis. 2009. Web.
O’Malley, CA. 2009. ‘Infection control in cystic fibrosis: Cohorting, cross-contamination, and the respiratory therapist. Respiratory Care, Vol. 54, No. 5, pp. 641-655.
Quinton, P. 2007. ‘Cystic Fibrosis: Lessons from the Sweat Gland.’ Physiology, Vol. 22, No. 3, pp. 212-225.
Rosaler, M. 2007. Cystic Fibrosis. The Rosen Publishing Group, New York.
Rowe, SM, Miller, S & Sorsche. 2005. ‘Cystic Fibrosis.’ The New England Journal Of Medicine. Vol 352, pp. 1992-2001.
Savopoulos, J & Oversteegen, L. 2006. ‘Cystic fibrosis: Big unmet needs small steps.’ Journal of Medical Marketing, Vol. 6, No. 3, pp. 158-164.