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Cystic fibrosis

Most common lethal genetic disorder
   
Defect: mutation of the chloride channel protein, cystic fibrosis trans-membrane conductance regulator (CFTR)

Genetics
  
i. CFTR gene is located on chromosome 7
ii. Most common mutation is a deletion in amino acid position 508 (AF508)

Pathogenesis: 
  • defective chloride channel protein leads to abnormally thick viscous mucous, which obstructs the ducts of exocrine organs

Distribution of disease

i. Lungs
  • Recurrent pulmonary infections with P. aeruginosa and S. aureus . 
  • Chronic bronchitis
  • Bronchiectasis


ii. Pancreas

  •  Plugging of pancreatic ducts results in atrophy and fibrosis
  •  Pancreatic insufficiency
  •  Fat malabsorption 
  •  Malodorous steatorrhea
  •  Deficiency of fat-soluble vitamins


iii. Male reproductive system

  • Obstruction of the vas deferens and epididymis
  • May lead to male infertility


 iv. Liver:

  •  plugging of the biliary canaliculi may result in biliary cirrhosis


v. GI tract:

  • small intestinal obstruction (meconium ileus)



Diagnosis

i. Sweat test (elevated NaCl)
ii. DNA probes

Treatment

  • Chest Physiotherapy
  • Antibiotics
  • Mucolytics : N-acetylcysteine
  • Gene therapy

Prognosis
i. Mean survival: 30 years
ii. Most common cause of death is pulmonary infections