Cystic fibrosis is an autosomal recessive disease that is the most common cause of progressive obstructive lung disease in children and young adults. The incidence in Caucasians is 1 in 2000 to 1 in 3000. The carrier rate is approximately 1 in 25. The cystic fibrosis gene is located on chromosome 7 and this codes for the cystic fibrosis transmembrane conductance regulator (CFTR) This protein regulates electrolyte transport across cell membranes and abnormalities lead to increased viscosity of secretions and obstruction of airways and other channels. There are 500 known mutations but 70 mutations are common and identify over 90% of patients with cystic fibrosis.
Common Clinical Characteristics
1. Pulmonary
a. Wheezing, cough, recurrent respiratory infections and pneumonia
b. Chronic cough, increased AP diameter of the chest, clubbing
2. Gastrointestinal
a. Fatty stools due to pancreatic exocrine insufficiency
b. Poor weight gain despite large appetite
c. Hypoproteinemia, edema, anemia, Vitamin deficiency
d. Hepatomegaly
3. Newborns
a. Meconium ileus
b. Meconium peritonitis secondary to perforation
c. Inspissated bile syndrome and cholestasis, prolonged jaundice
4. Sinus disease with panopacification of the paranasal sinuses
5. Absent vas deferens with resultant azospermia
6. Rectal prolapse
7. Pancreatitis
8. Nasal Polyps
Diagnosis
1. The sweat test remains the gold standard for diagnosis of cystic fibrosis.
2. 60 meq/liter sweat chloride plus characteristic findings and + family history is diagnostic
a. Other causes of increased sweat chloride include adrenal insufficiency, mucopolysaccharidoses, Glycogen Storage Disease type I, hypothyroid, familial hypoparathyroid, malnutrition, ectodermal dysplasia, and Lab error.
3. May be difficult to collect adequate sweat in newborns and genotyping for the CFTR mutation may be performed
4. It is imperative that this difficult to perform test is done in a lab that has experience doing the test.
Management of Cystic Fibrosis
1. Mobilization of airway secretions
a. Chest physiotherapy
b. Inhaled bronchodilators
c. Mucolytic agents N-acetylcysteine (Mucomyst) and rhDnase (Pulmozyme)
2. Treatment of Infections ( Staphylococcus aureus and Pseudomonas aeruginosa
a. Antimicrobials - oral, IV, and aerosols
3. Evaluation periodically with pulmonary function testing
4. Lung transplantation.
5. Treat airway reactivity with bronchodilators such as albuterol, Theophylline, and steroids
6. Pancreatic enzyme replacement with meals and snacks.
7. High protein and caloric diets
8. Vitamin supplementation for fat soluble vitamins- A. D. and E. Vitamin K until one year of age
9. Newborns
a. Gastrograffin enemas for meconium ileus
10. Monitor for hepatic disease, biliary obstruction, gallstones, and cirrhosis
11. 30% develop diabetes mellitus by 18 years of age.
12. Genetic counseling
Prognosis
1. Median survival about 30 years
