Cystic Fibrosis (CF)

Question 1

What is Cystic Fibrosis?

Answer 1

Autosomal recessive disorder affecting the mucus glands.

Question 2

Genetic Aetiology of Cystic Fibrosis.

Answer 2

Mutation of the CFTR (Cystic Fibrosis Transmembrane Conductance Regulatory) Gene on Chromosome 7 - commonest type : delta-F508 (cellular chloride channels).

Question 3

Pathophysiological Consequences of Cystic Fibrosis (3).

Answer 3

1. Thick Pancreatic and Biliary Secretions - Blockage of Ducts and Lack of Digestive Enzymes e.g. Lipase.
2. Low-Volume Thick Airway Secretions that reduce clearance - bacterial colonisation and susceptibility to airway infections.
3. Congenital Bilateral absence of vas deferent (infertility males).

Question 4

Symptoms of Cystic Fibrosis.

Answer 4

1. Chronic Cough with Thick Sputum.
2. Recurrent RTIs.
3. Steatorrhoea.
4. Abdominal Pain and Bloating.
5. Salty Kiss.
6. Failure to Thrive.
7. Rectal Prolapse (Bulky Stools).
8. Delayed Puberty.
9. Diabetes Mellitus.
10. Male Infertility and Female Subfertility.

Question 5

Signs of Cystic Fibrosis.

Answer 5

1. Failure to Thrive (Growth Chart).
2. Nasal Polyps.
3. Finger Clubbing.
4. Crackles and Wheezes.

Question 6

1st Sign of Cystic Fibrosis.

Answer 6

Meconium Ileus - usually black within 24 hours : here, no passing within 24 hours, vomiting, abdominal distension.

Question 7

Common Microbial Colonisers in Cystic Fibrosis (6).

Answer 7

1. S. aureus (prophylactic Flucloxacillin).
2. H. influenza.
3. K. pneumoniae.
4. E. coli.
5. B. cepacia.
6. P. aeurginosa (long-term nebulised antibiotics e.g. Tobramycin and Oral Ciprofloxacin).

Question 8

Diagnosis of Cystic Fibrosis (3).

Answer 8

1. Gold Standard : Sweat Test.
2. Newborn Blood Spot Heel PrickTesting (Day 5 - Day 9).
3. Genetic Testing for CFTR during pregnancy (Amniocentesis) or CVS (Postnatally).

Question 9

Method of Sweat Test.

Answer 9

1. Pilocarpine applied to a patch of skin (arm/leg).
2. Electrodes placed either side and small current is passed between causing sweat production.
3. Sweat is absorbed with lab-issued gauze and sent for testing of Chloride concentration.

Question 10

Results of Sweat Test.

Answer 10

Positive - More than 60mmol/L (normal < 40 mmol/L).

Question 11

Causes of False Positive Sweat Test.

Answer 11

1. Malnutrition.
2. Adrenal Insufficiency.
3. Glycogen Storage Disease.
4. Nephrogenic DI.
5. Hypothyroidism and Hypoparathyroidism.
6. G6PD.
7. Ectodermal Dysplasia.

Question 12

Cause of False Negative Sweat Test.

Answer 12

Skin Oedema - Hypoalbuminaemia and Hypoproteinaemia - Pancreatic Exocrine Insufficiency.

Question 13

Management of Cystic Fibrosis.

Answer 13

1. MDT.
2. Chest Physiotherapy 2x Daily (Clear Mucus and Reduce Infection Risk).
3. Exercise (improve Respiratory Function).
4. High-Calorie Diet & High-Fat Intake (Malabsorption).
5. CREON.
6. Prophylactic antibiotics.
7. Bronchodilators.
8. Nebulised DNase.
9. Nebulised Hypertonic Saline.
10. Vaccinations.

Question 14

What is Dornase Alfa?

Answer 14

Nebulised DNase - enzyme that breaks down DNA material in respiratory secretions making secretions less viscous and easier to clear.

Question 15

Monitoring of Cystic Fibrosis.

Answer 15

1. Every 6 Months.

2. Regular Monitoring - Diabetes, Osteoporosis, Vitamin D Deficiency, Liver Failure.

Question 16

When would a lung transplant be contraindicated in Cystic Fibrosis?

Answer 16

Chronic infection with B. cepacia.

Question 17

Prognosis of Cystic Fibrosis (5).

Answer 17

1. 90% - Pancreatic Insufficiency.
2. 50% - Diabetes.
3. 30% - Liver Disease.
4. Infertility.
5. Life Expectancy - 47 Years.