20. Cystic Fibrosis
Definition
Cystic fibrosis (CF) is an ultimately lethal inherited disorder. It predominately affects the function of endocrine glands, with wide-ranging effects on multiple organ systems, including the lungs, pancreas, intestines, and liver. CF is characterized by chronic pulmonary infections and inadequate pancreatic enzymes, along with other associated complications.
Incidence
In the United States, the incidence of cystic fibrosis in Caucasians of northern European heritage is 1:3200; in the African American population, 1:15,000; in the Hispanic population, 1:9200; and in the Asian American population, 1:30,000. Internationally, the occurrence ranges from 1:620 in a specific group of Dutch heritage to 1:90,000 among Asian populations.
Etiology
Cystic fibrosis is an autosomal recessive disease, the expression of which is a defect in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR encodes a protein that is a chloride channel regulated by cyclic adenosine monophosphate (cAMP). This mutation produces cAMP-regulated chloride transport abnormalities in epithelial cells’ mucosal surfaces. The subsequent chloride transport failure, along with the concomitant water transport abnormalities, culminates in very viscous secretions within the respiratory system, pancreas, gastrointestinal tract, sweat glands, and other exocrine tissues. The viscous secretions are tenacious and difficult to clear.
Lung disease is the most common reason for death among CF patients. The lungs develop quite normally in utero, are normal at birth, and for a period of time after birth. The thick, tenacious mucous secretions establish a scenario for infection that is followed by a neutrophilic inflammatory response. This cycle of infection followed by neutrophilic inflammation continues throughout the patient’s life. It eventually produces structural damage, impaired gas exchange, end-stage lung disease, and finally, early death.
Signs and Symptoms
• Abdominal distention
• Cheilosis
• Cough (dry and productive)
• Cyanosis
• Digit clubbing
• Dry skin
• Hepatosplenomegaly
• Hyperresonant chest
• Increased anteroposterior chest diameter
• Kyphosis
• Nasal polyps
• Parotid gland swelling
• Rectal prolapse
• Respiratory distress
• Rhinitis
• Scoliosis
• Submandibular gland swelling
• Tachypnea
• Wheezing
Medical Management
Cystic fibrosis affects multiple organs. Management is thus a multidisciplinary effort that may involve surgery (general, cardiothoracic, or transplant), endocrinology, otolaryngology, pulmonology, cardiology, and gastroenterology. Most often the patient with cystic fibrosis is treated primarily by a pulmonologist because of the prevalence of pulmonary symptoms. The viscous secretions commonly seen in the patient with cystic fibrosis create a persistent, rich growth medium for infectious organisms, such as Haemophilus influenza, Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus. The patient typically experiences recurrent bouts of respiratory/pulmonary infections that are treated with antibiotics. They are usually very well educated about the disease, even at a young age, and receive respiratory treatments every day. One goal of the treatments is to dramatically reduce the viscosity of the secretions and facilitate expectoration of the mucus. Daily chest physiotherapy and postural drainage are often required to help facilitate expectoration of the mucus.
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