Cystic Fibrosis

Question 1

Define cystic fibrosis.

Answer 1

Autosomal recessive condition characterised by recurrent lung infections, malabsorption + failure to thrive.

Question 2

What is the aetiology of cystic fibrosis?

Answer 2

Defect in cystic fibrosis transmembrane conducts regulator gene (CFTR; which codes a cAMP-regulated chloride channel)
80% due to delta F508 on Chr7

Question 3

Summarise the epidemiology of cystic fibrosis.

Answer 3

1/2500 live births.

More common in Caucasians.

Question 4

When is cystic fibrosis screened for in children?

Answer 4

At birth: heel prick test

Question 5

If cystic fibrosis screening is positive, what further tests are performed to confirm diagnosis?

Answer 5

Sweat test (abnormally high NaCl)
Genetic tests

Question 6

If no history of CF screening, what else can diagnosis be based on?

Answer 6

Clinical manifestations supported by sweat or gene results

Question 7

Describe results of sweat test in CF

Answer 7

Abnormally high sweat chloride
normal value < 40 mEq/l, CF indicated by > 60 mEq/l

Question 8

List 6 causes of a false positive sweat test

Answer 8

Malnutrition
Adrenal insufficiency
Glycogen storage diseases
Nephrogenic DI
Hypothyroidism, hypoparathyroidism
G6PD

Question 9

What is the most common reason for false negative sweat tests?

Answer 9

Skin oedema, often due to hypoalbuminaemia/ hypoproteinaemia secondary to pancreatic exocrine insufficiency.

Question 10

List 3 presenting symptoms of CF

Answer 10

Delayed passage of meconium/ meconium ileus

Malabsorption: Voracious appetite, Steatorrhoea, FTT (poor weight gain/ dropping deciles)

Recurrent chest infections

Question 11

List 6 features of CF that may present later in childhood/ early adulthood

Answer 11

Short stature
Diabetes mellitus
Delayed puberty
Rectal prolapse (due to bulky stools)
Nasal polyps
Male infertility, Female subfertility

Question 12

What are the signs of cystic fibrosis?

Answer 12

Signs of malnutrition: Muscle mass decreased

Resp: Wet cough, hyperinflation

Others: Clubbing, bilateral absence of the vas deferens

Question 13

What is seen on lung function testing in cystic fibrosis?

Answer 13

Obstructive picture with air trapping + hyperinflation (Decreased FEV1, Increased Total lung capacity).

Question 14

What is the long-term management for the respiratory symptoms of cystic fibrosis?

Answer 14

Specialist PT sessions to mobilise secretions.

Inhaled bronchodilator (salbutamol)

Inhaled mucolytic

Question 15

How frequent should physiotherapy be done for respiratory symptoms in CF?

Answer 15

Twice a day

Question 16

What is used for mucolytic therapy in cystic fibrosis?

Answer 16

1st line = rhDNase (Dornase alfa)
2nd line = rhDNase + hypertonic saline

Question 17

What additional therapy can be added on for respiratory management in CF?

Answer 17

Inhaled Tobramycin for initial/ chronic Pseudomonas infection.

Inhaled corticosteroid (if co-morbid asthma/ ABPA)

Ivacaftor: CFTR potentiator (only useful in G551D gene mutations).

Question 18

What respiratory intervention is reserved for CF patients who have all alternatives?

Answer 18

Bilateral lung transplant

Question 19

Name a contraindication to lung transplant in CF

Answer 19

Chronic infection with Burkolderia cepacia

Question 20

Why should CF patients try to minimise contact with each other?

Answer 20

To prevent cross infection with Burkholderia cepacia + Pseudomonas aeruginosa

Question 21

What is the long-term management for the GI symptoms of cystic fibrosis?

Answer 21

Specialist dietician: high calorie, inc. high fat intake

Pancreatic insufficiency: Pancreatin (pancreatic enzyme replacement)
+ fat-soluble vitamin supplementation.
+/- PPIs

Liver disease: Urosdeoxycholic acid to prevent gallstone development.

GORD: Famotidine (2nd PPIs)

Ivacaftor in specific CFTR mutations.

Question 22

What is the long-term management for non-specific symptoms of cystic fibrosis?

Answer 22

Psychological support + counselling for carer + patient.

Specialist nurses.

Specialist pharmacists.

Regular follow-ups + monitoring for complications.

Immunizations esp. for influenza + pneumococcus.

Question 23

What is the acute management for meconium intestinal obstruction?

Answer 23

Water-soluble contrast enema + osmotic agent (Lactulose)

NG decompression if still obstructed

Surgery if peritonitc

Question 24

What is the mangement for acute respiratory infection in cystic fibrosis?

Answer 24

Mild: Co-amoxiclav PO

Mod- Severe: IV Tobramycin

Regardless of severity:
Increased chest physiotherapy.
Bronchodilator, mucolytic.

Question 25

What are the possible complications of cystic fibrosis?

Answer 25

Respiratory: Bronchiectasis, cor pulmonale, pneumothorax, hemoptysis.

GI: Cirrhosis, portal hypertension, distal intestinal obstruction syndrome; viscid mucofaeculent material obstructs the bowel.

Endocrine: DM, decreased fertility. 99% of males are infertile due to obstruction + abnormal development of vas deferens.

Psychological

Question 26

What is the prognosis of cystic fibrosis?

Answer 26

Most survive into adult life (median survival 40y).
Children with Pseudomonas colonization have a 2–3-fold increased mortality over 8y.