Cystic Fibrosis

Question 1

Describe Cystic Fibrosis in 3 ways

Answer 1

• Autosomal Recessive
• Mutation in CFTR Protein, leading to multi-system disease
• Characterised by thickened secretions

Question 2

What are 2 functions of the CFTR protein in the airway?

Answer 2

• Secretes Cl- and HCO3- ions into airway lumen
• Regulates Na absorption from airway lumen via ENaC channels

(Reduced Cl secretion-> Dehydration due to increased Na absorption, Increased viscosity)

Question 3

What is the most common CFTR mutation? (Over 200 exist)

Answer 3

Phe508del (Phenylalanine deletion)

Question 4

How is CF diagnosed?

Answer 4

• Any characteristic phenotype feature OR CF history in sibling OR positive new-born screening result

AND

• Increased sweat [Cl] OR identification of 2 CF mutations OR evidence of abnormal nasal epithelial ion transport

Question 5

Other than New-born screening, how does CF present in 4 ways?

Answer 5

1. Meconium ileus (15-20% of CF new borns);
   - Bowel blocked by sticky secretions
2. Intestinal malabsorption (>90%);
   - Severe deficiency of Pancreatic Enzymes due to blockage of Exocrine glands
3. Recurrent Chest Infections
4. Atypical presentations with milder disease, if patients have mutations that cause faulty, but not entirely malfunctioning CFTR protein

Question 6

Does Atypical CF typically appear in adults or children

Answer 6

Adults (Hence Atypical, as normally diagnosed within first 20 years)

Question 7

List 4 Complications of CF (not an exhaustive list)

Answer 7

• CF related diabetes
• Respiratory infections
• Low body weight
• Distal Intestinal Obstruction Syndrome (DIOS)

Question 8

How does CF lead to low body weight and how can it be treated?

Answer 8

Due to pancreatic enzyme deficiency and malabsorption

• Pancreatic enzyme replacement therapy
• High calorie intake + supplements
• NG/ PEG tube feeding (especially in children with severe disease)

Question 9

Describe Distal Intestinal Obstruction Syndrome

Suggest 4 causes of this due to CF

Answer 9

• Intestinal obstruction in Distal Ileum and Proximal Colon
  (In constipation, obstruction is in whole bowel)
• Insufficient pancreatic enzyme prescription
• Non compliance (patient doesn’t take meds)
• Salt deficiency
• Hot weather

Question 10

How can Distal Intestinal Obstruction Syndrome (DIOS) be diagnosed?

Answer 10

• Palpable Right Iliac Fossa mass (faeces)

- Abdominal X-Ray showing faecal loading at junction of small and large bowel

Question 11

What advice would you give to someone with CF?

8 things

Answer 11

• No smoking
• Avoid other CF patients (Can acquire multiple pseudomonas colonisations with different resistances)
• Avoid people with infections
• Avoid jacuzzis (Pseudomonas)
• Clean and dry nebulisers
• Avoid stables/ compost etc. (Risk of Aspergillus inhalation)
• Vaccinations (Flu and Strep pneumoniae)
• NaCl tablets in hot weather/ vigorous exercise