Cystic Fibrosis

Question 1

Cystic fibrosis cause

Answer 1

Characterised by a disorder in epithelial transport of chloride (Cl-) secondary to a variety of mutations in the chloride channel protein encoded by the CF transmembrane conductance regulator (CFTR gene on chromosome 7) in exocrine glands and in the epithelium of the respiratory, gastrointestinal and reproductive tracts.

Question 2

Sweat glands in CF patients

Answer 2

In the sweat glands of CF patients sodium and chloride absorption decreases resulting in salty sweat and forms the basis of the ‘sweat test’ (defined by high chloride content in sweat).

Question 3

Respiratory and intestinal epithelium in CF patients

Answer 3

Abnormal function of the CFTR results in increased Na+ resorption (and reduced Cl- secretion). This results in passive H2O absorption resulting in dehydrated mucous which obstructs the airways.

Question 4

Complications of CF

Answer 4

Abnormally thick mucous secretion obstruct organ passages resulting in:

• Recurrent pulmonary infections
• Pancreatic insufficiency
• Steatorrhoea (lack of pancreatic enzymes reaching the intestine)
• Malnutrition
• Cirrhosis
• Intestinal obstruction (meconium ileus in neonates); and
• Male infertility (CF associated with bilateral absence of the vas deferens).

These manifestations can occur any point in early life, even in adolescence.

Question 5

Treatment of CF

Answer 5

Aggressive management of lung infections and replacement of pancreatic enzymes.

Question 6

Prognosis

Answer 6

Tends to depend on lung disease. Lung transplant.