Pathophysiological Defects of Cystic Fibrosis

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Table of Contents

Autosomal Recessive Inheritance Pattern for CF
Role of Goblet Cells and Cilia in Cystic Fibrosis
Symptoms of Cystic Fibrosis
Diagnosis of CF
Pancreatic Enzymes Involved in CF
Medical Action
Nursing Diagnoses for PJ
References

The gene responsible for cystic fibrosis is cystic fibrosis trans-membrane regulator (CFTR) (McCool, 2006, 51). It issues instructions that lead to formation of channels which allow movement of chloride ions across cell surfaces (McCool, 2006, 52). In this case, the abnormalities in CFTR interfere with such channels. CFTR gene can have mutations in a number of ways leading to different abnormalities in the CFTR protein (Chang, 2006). Some mutations can lead to formation of proteins that don’t fold as they should. Such proteins are prone to faster degradation. Some proteins may be shorter than expected (Grossman & Lisa, 2005). According to Grossman and Lisa, CFTR mutation can also lead to under-production of CFTR proteins. Other proteins may prohibit movement of ions across cell membranes; thereby defeating the purpose for which they exist (Grossman & Lisa, 2005).

CFTR proteins act as links connecting inner and outer sides of cells. They control movement of halogens across cell membranes (Grossman & Lisa, 2005, 7). This abnormal movement of salts which have high water affinity leaves mucus highly dehydrated (McCool, 2006, 48). Since this mucus can’t flow well, it accumulates in airways, tracts and ducts. The resulting obstruction complicates breathing and food digestion and absorption. Some bacteria can thrive in the accumulated mucus and damage lungs.

Autosomal Recessive Inheritance Pattern for CF

CF is inherited through genes. This condition will only prevail if both copies of partner chromosomes have the abnormality (McCool, 2006, 53). Someone with one copy that is affected and another copy that is not affected will not show CF symptoms. He is only said to be a carrier. Therefore, a baby will only suffer from CF complication if the mother and the father are at least carriers.

Punnett Square

	C	c
C	CC	Cc
c	Cc	cc

C represents the normal copy of the gene and c represents the abnormal copy. There are four possible outcomes. CC means that the father and the mother will each contribute one unaffected copy to the baby. Therefore, there is a probability of 0.25 that the baby will not be affected by CF either as a carrier or as a patient. Cc means that the child can inherit a normal copy from the father and abnormal copy from the mother or abnormal copy from the father and a normal copy from the mother. Therefore, there is 0.25 + 0.25 = 0.5 chance that the baby will have one copy affected and the other one not affected. In the last case scenario, cc means that the child will inherit one abnormal copy from each parent. Therefore, there is a probability of 0.25 that the child will be a CF victim(McCool, 2006).

Role of Goblet Cells and Cilia in Cystic Fibrosis

Goblet cells are located in the epithelium. There function is to produce mucus which comprises of mucins, water, and ions that protect airways and lungs by sieving the inhaled material (Afzelius, 2004). It is necessary to clear this mucus from the tracts to avoid blockages. The presence of water reduces mucus thickness to facilitate this clearance (Afzelius, 2004). Such mucus has sufficient water in normal people. In CF people, it lacks enough water. The resulting difficulty in mucus clearance leads to its accumulation it’s in the tracts. Apart from causing goblet cells to increase mucus production, cystic fibrosis also stimulates their increase in number (Knowles & Boucher, 2002).

Goblet cells have projected structures called cilia (Knowles & Boucher, 2002, 572). By beating, these structures cause mucus to move. In normal people, the presence of water provides necessary lubrication for cilia to beat. In CF people, lack of water impairs cilia beating. As a result, mucus piles in the tracts (Knowles & Boucher, 2002).

Symptoms of Cystic Fibrosis

PJ has a poor weight gain due to his inability to digest food (Machen, 2006). His smelly stool is due to poor digestion and absorption of fats and proteins. His high appetite is caused by lack of nutrients in the body as a result of poor food digestion and absorption. From the frequent lung infections,it can be said that there is stagnated mucus which is providing breeding grounds for bacteria. Coughs were caused by the body’s attempt to open airways (Machen, 2006).

Other symptoms will include delayed puberty due to lack of proper nutrition and delayed growth. It can also cause infertility in men due to blocked movement of sperms during ejaculation and in women due to blocked movement of sperms after copulation. Cases of diabetes may also indicate CF. Damages on the pancreas may impair production of sufficient insulin which is responsible for controlling blood sugar. It can also manifest in form of liver diseases due to blockages in bile ducts (Machen, 2006).

Diagnosis of CF

Salt test is the most recommended and frequently used approach in the CF diagnosis (Machen, 2006, 220). The defects associated with CF affect salt movement across cell surfaces. The unabsorbed salt is excreted through the skin in form of sweat. This means that the sweat of CF patients will have excess salt as compared to normal people. Therefore, if the salt content goes beyond a certain level, (normally 60mEq/L), the person is concluded to have cystic fibrosis (Machen, 2006, 221).

Pancreatic Enzymes Involved in CF

Blockage of pancreatic ducts prevents enzymes such as pancrelipase from getting to the intestines to breakdown food. Due to this blockage, other enzymes such as amylase and protease won’t help in breakdown of starch and proteins respectively. The results are proteins and fats in stool and lack of nutrition in the body (Nadels et al, 2005).

Medical Action

Zosyn is an antibiotic that is used to treat bacterial infections (Flume, et al, 2007). Apart from killing the bacteria that thrive in the accumulated mucus, it also prevents further bacterial infection. Albuterol eases breathing in CF patients by initiating broncho-dilation (Nadels et al, 2005, 1217). Flucticasone propionate is an anti-inflammatory drug used to reduce proinflammatory cytokines associated with the airways inflammation by reversing the stimulation of lipopolysaccharide (Nadels et al, 2005, 1219). Pancrelipase enzyme supplement is taken to break down food for ease of digestion. Amylase is taken to break down starch while protease is taken to break down proteins.

Nursing Diagnoses for PJ

PJ has imbalance in nutrition due to poor digestion and absorption of food. He should be given artificial enzymes such pancrelipase, amylase and protease to aid in digestion. The nurse should include this in his meals (Nadels et al, 2005).

PJ has improper clearance of airways due to mucus thickness. He should be given drugs that cause bronchodilation such as Albuterol. The nurse should ensure that he takes a lot of liquids to make the mucus less thick (Hazle & George, 2010).

PJ has not effectively coped with the disease. He should be given a counselling therapy. The nurse should get the patient to appreciate the treatment procedures and follow all the instructions given by the doctor (Nadels et al, 2005).

References

Afzelius, B.A. (2004). Cilia-related Diseases. Journal of Pathology. 204:470–7.

Chang, A.B. (2006). The Physiology of Cough. Paediatric Respiration 7:2–8.

Flume, P., et al. (2007). Cystic Fibrosis Pulmonary Guidelines: Chronic Medications for Maintenance of Lung Health. Journal of Respiratory Critical Care Medicine. 176: 957-969.

Grossman, Sheila, & Lisa C. Grossman, BA, MPH. (2005). Pathophysiology of Cystic Fibrosis Implications for Critical Care Nurses: Journal for High Acuity, Progressive and Critical Care Nursing. 25(4). 46-51.

Hazle, Leslie & George, Cynthia. (2010). Cystic Fibrosis Camplications: American Journal of Nursing. 110(12): 11-14.

Knowles, M. R. Boucher R. C. (2002). Mucus Clearance as a Primary Innate Defense Mechanism for Mammalian Airways. Journal of Clinical Investigations 109:571–7

Nadels, M. A. Boucher R. C. Knowles M. R. Jankaskas J. R. (2005). Cystic Fibrosis: Respiratory Medicine, 2(1), 1217–51.

Machen, T. E. (2006). Innate Immune Response in CF Airway Epithelia: Hyper-Inflammatory?Journal ofCell Physiology 291:C218–30.

McCool F. D. (2006). Global Physiology and Pathophysiology of Cough: ACCP Evidence-Based Clinical Practice Guidelines.129:48–53.

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