Cystic fibrosis

Question 1

What condition should you suspect in an infant with loose stools, recurrent chest infections and faltering growth?

Answer 1

Cystic fibrosis

Question 2

What is the inheritance pattern of cystic fibrosis?

Answer 2

• Autosomal recessive inheritance
• Defect in the CFTR gene which encodes a chloride channel

Question 3

How common is CF?

Answer 3

Affects 1 in 2500 births and carrier rate is 1 in 25

Question 4

Which organisms colonise CF patients?

Answer 4

• Staphylococcus aureus
• Pseudomonas aeruginosa
• Burkholderia cepacia*
• Aspergillus

Question 5

What is the life expectancy in cystic fibrosis?

Answer 5

40s

Question 6

What is the most common mutation causing cystic fibrosis? Which chromosome is it located on?

Answer 6

ΔF508 (78% of cases in UK)

Chromosome 7

Question 7

What is the pathophysiology of CF?

Answer 7

Lungs - reduction in the airway surface liquid layer and consequent impaired ciliary function and retention of mucopurulent secretions –> infections with e.g. Pseudomonas aeruginosa

Intestines - thick meconium produced –> meconium ileus in 10-20% of infants with CF

Pancreas - ducts blocked by thick secretions causing pancreatic enzyme deficiency (lipase, amylase, protease) and malabsorption

Sweat glands - abnormally high sodium and chloride

Question 8

How is CF detected in newborns?

Answer 8

Heel-prick

Immunoreactive trypsinogen (IRT) detection - genetic screening follows

Question 9

What are the clinical features of cystic fibrosis seen in a newborn?

Answer 9

Diagnosis through heel-prick

meconium ileus

Question 10

What are the clinical features of cystic fibrosis seen in an infant?

Answer 10

chronic chest infections

failure to thrive

prolonged neonatal jaundice

malabsorption, steatorrhoea

Question 11

What are the clinical features of cystic fibrosis seen in a young child?

Answer 11

Sinusitis

Bronchiectasis

Nasal polyps

Rectal prolapse

Question 12

What are the clinical features of cystic fibrosis seen in an older child/adolescent?

Answer 12

Haemoptysis or pneumothorax

ABPA (allergic bronchopulmonary aspergillosis)

Diabetes mellitus

Portal hypertension and cirrhosis

Distal intestinal obstruction

Sterility in males

Question 13

How do you demonstrate pancreatic insufficiency?

Answer 13

Low fecal elastase

Question 14

How is the sweat test done and what is diagnostic for CF?

Answer 14

Cl of 60-125mmol/L is diagnostic for CF (N: 10-40mmol/L)

Sweat is produced by passing low current voltage through pilocarpine on the skin and sweat is absorbed by filter paper

Question 15

Why are males with CF infertile?

Answer 15

Absence of the vas deferens

(women usually have normal fertility)

Question 16

Why are CF patients advised not to socialise with other CF patients?

Answer 16

Increasing spread of virulent strains of Pseudomonas and BURKholderia

Question 17

What is the only treatment option for end stage CF lung disease?

Answer 17

Bilateral sequential lung transplantation

Question 18

What is the nutritional management of CF?

Answer 18

Calorie intake should be 150% of normal - achieved by overnight gastrostomy feed

Pancreatic enzymes replacement

Fat soluble vitamin replacements

Question 19

Briefly summarise the respiratory management of CF.

Answer 19

1. FEV1 measurements/spirometry to assess disease progression
2. Prophylactic antibiotics (usually flucloxacillin)
   
   • 14 day antibiotic courses in persistent symptoms, may need to be via Portacath
3. Physiotherapy twice a day - chest percussion/postural drainage
4. Nebulised hypertonic saline/DNAse - help clearance, decrease viscosity
   
   • In pseudomonas infection, daily nebulised antipseudomonal antibiotics

Question 20

Which triad is useful in the diagnosis of CF?

Answer 20

The diagnosis of cystic fibrosis is usually based not on a single sign or test, but rather on a triad of:

1. Typical pulmonary and/or gastrointestinal tract manifestations
2. A family history
3. A positive result on ‘sweat-test’ (based on Cl-ion concentration).

Question 21

What is seen here?

Answer 21

Lungs in CF

• Hilar enlargement
• Hyperinflation
• Lobar atelectasis
• Bronchiectasis

NB:Increasing bronchial wall thickening and bronchiectasis. Progressive air-trapping with bronchiectasis may be initially apparent in the upper lobes but may progress to all zones. With advancing pulmonary disease there may be pulmonary nodules resulting from abscesses and atelectasis and marked hyperinflation with flattened domes of the diaphragm. Pulmonary artery dilatation and right ventricular hypertrophy associated with cor-pulmonale is usually masked by the hyperinflation