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Cystic Fibrosis
Definition
Cystic Fibrosis (CF) is a genetic disorder that causes the body to produce an abnormally thick, sticky mucus. This is due to the faulty transport of sodium and chloride within cells lining organs such as the lungs and pancreas. The thick mucus in the lungs can cause chronic infection and damage to the lungs. This thick mucus also obstructs the pancreas, preventing enzymes from reaching the intestines to help break down and digest food.Genetics
CF is the most common lethal genetic disease among whites (1), occurring once in every 2,500 to 3,200 live births. (Among African Americans the incidence is one in 115,000 births, among Asians one in 31,000, among Hispanics one in 9,200, and among the Native American population one in 10,900)(2). The disease is an autosomal recessive disorder caused by an abnormality in the cystic fibrosis transmembrane regulator (CFTR) protein. The result is an increased level of sodium reabsorption and decreased chloride secretion.
In recent years great strides have been made in the understanding of the etiology, pathophysiology and genetics of CF. In 1989 the CF gene was discovered on the long arm of chromosome 7. The most common mutation is called delta F508 and accounts for 67% of CF alleles among whites (1). However, more than 600 CF gene mutations have been identified (4). These discoveries may lead to improved treatment of CF, including gene therapy.
Clinical Findings
CF has a wide range of clinical manifestations with a variable pattern of onset and a broad spectrum of severity. The disorder is characterized by widespread dysfunction of the exocrine glands, so that they produce abnormally thick and viscous mucus throughout the body. Numerous secondary complicating features affect most organ systems. The predominant clinical manifestations are (a) chronic obstructive infectious pulmonary disease caused by the abnormally thick mucus secretions that completely or partially obstruct airways; (b) inability to release pancreatic enzymes for digestion into the small intestine, and (c) elevated sodium and chloride concentrations in sweat (1). The median survival age in the United States is 31 years; it is difficult to estimate life expectancy for young children due to recent advances in treatment (3).
Pathophysiology
The pulmonary disease picture is a cycle (usually measured in years) of acute and chronic bacterial pulmonary infection, excessive inflammation as well as impaired ciliary function. This leads to excess mucus secretion and bronchial obstruction, infection and inflammation resulting in bronchiectasis (7). Related pulmonary complications of CF include nasal polyps, sinusitis, asthma, allergic bronchopulmonary aspergillosis (ABPA) pneumothorax and hemoptysis (7).
Pancreatic function may be completely abated, partially active, or normal, although some compromise of exocrine function usually exists (1). Blockage of pancreatic enzymes and inadequate bile acid and bicarbonate cause malabsorption of fats, including essential fatty acids, proteins, and fat-soluble vitamins. If untreated, the result is diarrhea, steatorrhea, azoterrhea, vitamin deficiencies, and edema (4).
As a person with CF ages and pancreatic function diminishes, glucose intolerance may result. Diabetes mellitus develops in up to 15% of older patients (5). Other potential gastrointestinal complications include meconium ileus, intestinal obstruction, gallbladder disease, and biliary cirrhosis.
Women with CF have normal reproductive organs but puberty and the onset of menstruation can be delayed by a few years. Studies show that up to 20% of women with CF experience infertility. One reason for this is the thick cervical mucus, which acts as a barrier to sperm. However, many women with CF do conceive and give birth. In such cases, the physical stress of the pregnant woman with CF and the life expectancy of the mother are issues that must to be addressed. Men with CF have normal external reproductive organs, but again in some cases, puberty is delayed a few years. The majority (97% to 98%) of men with CF are infertile due to azospermia, caused by abnormalities of the reproductive ducts essential for normal sperm production (6).
Treatment and Management
The pulmonary disease picture is a cycle (usually measured in years) of acute and chronic Removal of the thick mucus from the lungs is an important component of therapy to maintain optimal lung function. Various modes of therapy include postural drainage with percussion; alternative airway clearance techniques such as Flutter valve, positive expiratory pressure (PEP), active cycle of breathing technique (ACBT), mechanical vest, autogenic drainage; and exercise therapy are all used to effect mucus removal. Mucolytic agents may be used to augment the removal of mucus.
The use of bronchodilator therapy is controversial, but patients with CF who have documented airway hyperreactivity may benefit from such therapy. Corticosteroid therapy has a role in the treatment of allergic bronchopulmonary aspergillosis. It may also be considered for infants with severe bronchiolitis and patients with significant airway obstruction unresponsive to bronchodilators (7).
Antibiotics may be used acutely or chronically and are usually selected on the basis of the results of sputum cultures. They may be given as oral, inhaled or intravenous formulations. Intravenous antibiotics are the treatment of choice for the episodic acute pulmonary exacerbations of CF. Manifestations of an exacerbation include increased cough, sputum production, and respiratory rate, and significant weight loss, low-grade fever, fatigue and malaise. As the disease progresses Pseudomonas aeruginosa is the most frequent pathogen. The antibiotics selected are often a combination of semisynthetic penicillin and an aminoglycoside such as tobramycin, which have been shown to have synergistic effects against Pseudomonas in vitro (7).
Most of the morbidity and nearly all of the mortality associated with CF are caused by the progressive pulmonary disease. Pulmonary function deteriorates over time eventually resulting in respiratory failure. At present the only effective treatment or therapy for patients with end-stage CF and severe dysfunction of both the heart and the lungs is a heart-lung transplant. This usually results in marked improvement in lung function and no recurrence of the chronic lung infections. This is a relatively new therapy and the long-term survival rates are unclear (7).
For those with intestinal symptoms, oral replacement of pancreatic enzymes, fat soluble vitamins (A, E, D, K) and high-calorie diet help control the symptoms and improve nutritional status. Major nutritional emphasis is to provide adequate calories to compensate for malabsorption and the higher metabolic rate caused by infection and increased work of breathing. Additional medications that may be used include antacids, H2 blockers, prokinetic agents, urosodeoxycholic acid. Supplementary sodium chloride is needed in hot weather or with increased activity.
Care Coordination
Proper management of patients with cystic fibrosis requires a broad understanding of the disease pathology and knowledge of the secondary physical, psychological, social, and financial manifestations. This necessitates an interdisciplinary approach. The interdisciplinary specialists at a CF Center coordinate ongoing CF care of the chronically ill patient in the context of his or her family and community. Open and clear communication between the child and family, primary care providers and CF Center is an ongoing and essential process (1,5).
The CF Foundation accredits its 115 CF Centers in the United States, supports research, and maintains a national registry. Services that the CF Centers provide include sweat testing, designation and evaluation of therapeutic programs, education of family and child, instruction in pulmonary therapy and nutrition, genetic, vocational, and financial counseling.
One of many websites about CF is: the National Cystic Fibrosis Foundation site http://www.cff.org
- Shabbat - Hebrew word for Sabbath. Shabbat in the Jewish religion is the day of rest and worship. Shabbat begins Friday at sundown and ends on Saturday at sundown.
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3. Wilfond BS, Taussig LM. Cystic fibrosis: General overview. In Taussig LM, Landau LI, eds. Pediatric Respiratory Medicine. St Louis: Mosby; 1999:982-990.
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6. Lemke AA, Facts on fertility. In: Ramsey BW, Hodson ME , et al. New Insights into Cystic Fibrosis. Califon, NJ: Gardiner-Caldwell Syner-Med; 1995:12.
7. Fiel SB, Part G 4 Cystic fibrosis. In: Bone RC, Dantzker DR, George RB, Matthay RA, Reynolds HY, eds. Pulmonary & Critical Care Medicine, 1998 ed., Mosby-Year Book, Inc. 1998:1-12.
8. Abraham, Lev. Medical Halachah. A comprehensive guide to Jewish medical law in sickness and health. 1980: London: Feldheim Publishers.
9. American Academy of Pediatrics, Committee on Children with Disabilities. Counseling families who choose complementary and alternative medicine for their child With chronic illness or disability. Pediatrics; March 2001;107(3), pp. 598-601.
10. American Academy of Pediatrics, Committee on Bioethics. Religious objections to medical care. Pediatrics; February 1997; 99 (2): 279-281.
11. American Academy of Pediatrics, Committee on Pediatric Workforce. Culturally effective pediatric care: education and training issues. Pediatrics; January 1999; 103 (1): 167-170