Cystic Fibrosis

Question 1

What is cystic fibrosis?

Answer 1

Autosomal recessive disorder of the cystic fibrosis transmembrane conductance regulator (CFTR)

Question 2

What chromosome is affected and what is the inheritance pattern?

Answer 2

chromosome 7 (Delta F508). 1:2500.

Autosomal recessive

Question 3

What does the faulty gene cause in CF?

Answer 3

Induces low salt and chloride excretion into airways leading to increased viscosity of secretions

Question 4

How does CF present?

Answer 4

• Lung: recurrent chest infections, bronchiectasis
• ENT: nasal polyps and sinusitis
• GI: Meconium ileus, malabsorption, intestinal obstruction, steattorrhoea (pancreatic insufficiency)
• Other: Fertility, arthropathy

Question 5

What investigations should be used in CF?

Answer 5

1. Sweat electrolyte test
   - Chloride >60 is diagnostic
2. CXR
   - Peribronchial thickening (but can be normal)
3. CT (HR)
4. DNA analysis for genotype

Question 6

What is the management of CF?

Answer 6

1. Antibiotics
2. Pancreatic/nutritional supplements
3. Inhaled antibiotics, steroids and recombinant human DNase
4. CFTR gene therapy
5. Lung transplant

Question 7

What are the complications of CF?

Answer 7

1. DM (10%) – treat with insulin
2. ABPA (15%)
   - High dose steroids
3. Infections
4. Osteoporosis
5. Liver disease