Cystic Fibrosis

Basics

Description

Cystic fibrosis (CF) is an inherited autosomal recessive disorder, characterized by chronic obstructive lung disease, pancreatic exocrine insufficiency, and elevated sweat chloride concentration.

ALERT
  • Due to variability in presentation, the most common pitfalls are failure to diagnose and initiate therapies in a timely manner.
  • Diagnosis may be delayed in patients with mild or atypical symptoms.

Epidemiology

  • Most common lethal inherited disease in the Caucasian population
  • Carrier frequency of mutations in the CF transmembrane conductance regulator (CFTR) gene:
    • 1:29 in Caucasians
    • 1:49 in Hispanics
    • 1:53 in Native Americans
    • 1:62 in African Americans
    • 1:90 in Asians

Prevalence

  • 1:3,300 in Caucasians
  • 1:9,500 in Hispanics
  • 1:11,200 in Native Americans
  • 1:15,300 in African Americans
  • 1:32,100 in Asians

Risk Factors

Genetics

CFTR gene

  • Located on the long arm of chromosome 7
  • Most common mutation results in deletion of phenylalanine at position 508 in the CFTR glycoprotein.
  • The Δ508 mutation occurs in ~70% of CF patients.
  • >1,700 mutations have been reported in the CFTR gene.
  • Presence of gene modifiers may cause incomplete phenotypic presentations.

General Prevention

Prepregnancy carrier detection

Pathophysiology

  • CFTR
    • Membrane glycoprotein, which functions as a cyclic AMP–activated chloride channel at the apical surface of epithelial cells
    • An abnormality in CFTR results in defective chloride conductance.
    • May have other roles in the regulation of membrane channels and the pH of intracellular organelles; may affect cell apical sodium channel regulation
    • CFTR abnormalities may act as binding sites for Pseudomonas aeruginosa, promoting proinflammatory responses in the lung.
  • In the respiratory system
    • Increased mucus viscosity
    • Early bacterial colonization despite a robust neutrophilic inflammatory response
    • Mucous plugging and atelectasis
    • Bronchiectasis and emphysema develop.
    • Abnormal nasal sinus development
  • In the gastrointestinal (GI) tract
    • Progressive pancreatic damage leads to exocrine pancreatic insufficiency.
    • Endocrine pancreatic dysfunction
    • Focal biliary cirrhosis of the liver
    • Hypoplasia of the gallbladder and impaired bile flow

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