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Snapshot
  • A 3-year-old boy with a history of recurrent pneumonia and chronic diarrhea. His mother states that he has 6-8 four smelling stools per day. PE reveals a low grade fever, scattered rhonchi over both lung fields, crepitant rales at the left lung base and dullness to percussion. 
Introduction
  • Cystic fibrosis is a genetic disorder leading to excessive, viscous secretions that plug exocrine glands
    • autosomal recessive disorder
    • caused by mutations in CFTR gene (chloride channel) on chromosome 7
      • CFTR is a transmembrane cAMP-activated ion channel 
      • 3 nucleotide deletion
        • most common mutation is 508 Phe del 
      • result is instability of CFTR protein and premature degradation by Golgi apparatus
      • inability to alter ionic gradients of Cl- results in mucus dehydration
  • Affects multiple organ systems with widespread exocrine gland dysfunction
    • pancreatic exocrine insufficiency is responsible for most of them
  • Epidemiology
    • most common genetic disease in the United States
    • mostly affects Caucasians
    • Newborn screening now routine in all states
Presentation
  • Symptoms
    • respiratory symptoms are more prominent in adulthood
      • recurrent pulmonary infections
        • Pseudomonal spp and S. aureus are most common
      • chronic sinusitis
      • chronic, productive cough
      • dyspnea on exertion
      • hemoptysis
    • gastrointestinal symptoms are more prominent in infancy
      • chronic, frequent diarrhea
        • greasy stool with flatulence from malabsorption secondary to pancreatic insufficiency
        • can lead to rectal prolapse
      • meconium ileus in infants (15%)
      • pancreatitis 
    • other symptoms
      • calcium oxalate kidney stones
        • secondary to fat malabosorption
  • Physical exam
    • failure to thrive (50%)
    • respiratory compromise (50%)
    • "salty taste"
    • cyanosis
    • digital clubbing
    • ronchi
    • rales
    • hyperresonance of chest to percussion
    • nasal polyposis
Evaluation
  • CXR
    • hyperinflation
    • prominent bronchovascular markings
      • bronchiectasis with "tram tracks" and peribronchial cuffing
      • diffuse bronciectactic changes
  • Sweat chloride test
    • historical diagnostic gold standard
    • >60 mEq/L in patients <20 years old
    • >80 mEq/L in adults
  • Genetic testing
    • confirms disease by identification of specific genetic mutation
  • Immunoreactive trypsinogen assay
  • Nasal transepithelial potential difference
  • Pulmonary function testing
    • often abnormal before first birthday
    • obstructive pattern with increased lung volumes (TLC and RV) over time from air trapping and hyperinflation
    • reduced diffusing capacity (DLCO)
Differential
  • Inherited immunodeficiency (SCID, CVID)
  • Primary ciliary dyskinesia
Treatment
  • Lifestyle
    • health maintenance
      • nutritional counseling
      • psychiatric/psychologic support indicated in most patients with or without mental instability
      • up-to-date immunizations indicated in all patients
  • Pharmacologic
    • respiratory therapy
      • indicated in all patients
      • includes several components including
        • chest physiotherapy (percussion, positive pressure, nebulizers)
        • bronchodilators
        • inhaled corticosteriods 
          • if asthmatic component or ABPA
        • DNA-ase and hypertonic saline
        • antibiotics 
          • chronic macrolide therapy common
          • IV antibiotics for acute exacerbations
        • anti-inflammatory agents (ibuprofen)
    • pancreatic enzymes and fat-soluble vitamins
      • indicated for malabsorption
  • Operative
    • lung and pancreas transplantation
      • indicated for most severe, but only if patient can tolerate surgery
Prognosis, Prevention, and Complications
  • Prognosis
    • while patients are living longer and more complete lives with modern medicine, rarely do CF patients live beyond 40 years of age without transplantation
  • Prevention
    • immunization for influenza and pneumococcus can prevent infections
    • embryonic selection, although controversial, has been used by known carriers or affected couples to prevent transmission of the disease to their children
  • Complications
    • chronic hypoxemia and hypercapnia lead to pulmonary hypertension
      • patients often develop cor pulmonale (RHF)
    • Recurrent, drug-resistent bacterial or fungal pneumonias
      • classically Pseudomonas
    • idiopathic hyponatremia
    • CF-related diabetes mellitus
    • fat-soluble vitamin deficiency (low vitamin A, D, K, and E)  
    • esophageal varices
    • biliary cirrhosis and cholelithiasis
    • infertility (95%)  
      • absence/obliteration of the vas deferens
    • heat exhaustion (poor sweating)
 

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