Cystic Fibrosis

Question 1

What is cystic fibrosis?

Answer 1

An autosomal recessive condition that leads to abnormally viscous mucous blockages of many tubular structures including conducting airways and lungs

Question 2

What is the median survival for cystic fibrosis?

Answer 2

41 years

Question 3

What causes cystic fibrosis?

Answer 3

Mutation in the CFTR channel, which carries Cl

This leads to less Cl and more Na and H2O, causing thick, sticky secretions

Question 4

Which chromosome will contain the mutation for cystic fibrosis?

Answer 4

Chromosome 7

Question 5

What are the two possible mutations that can cause cystic fibrosis?

Answer 5

G551D

F508del

Question 6

What is the best diagnostic indicator for cystic fibrosis?

Answer 6

The sweat test

Question 7

What are some organs that cystic fibrosis affects?

Answer 7

Sweat glands
Lungs
Reproductive organs
Pancreas
Intestines

Question 8

What result in the sweat test indicates a referral to a CF centre as it is likely CF?

Answer 8

> 60 mmol/L

Question 9

What are the symptoms of cystic fibrosis affecting the lungs?

Answer 9

Wet-sounding cough
Recurrent infections
Chronic sinusitis
Bronchiectasis
Nasal polyps

Question 10

What can cystic fibrosis cause in the reproductive organs?

Answer 10

Bilateral absence of the vas deferens

Question 11

What are the symptoms of cystic fibrosis affecting the pancreas?

Answer 11

Failure to thrive and poor weight gain with voracious appetite in kids
Exocrine - steatorrhoea
Endocrine - diabetes mellitus
Gallbladder stones, liver cirrhsis

Question 12

What are the symptoms of cystic fibrosis affecting the intestines?

Answer 12

Failure to pass meconium (meconium ileus)

Digital intestinal obstruction syndrome in young adults

Question 13

What are signs of cystic fibrosis?

Answer 13

Cyanosis
Finger clubbing
Bilateral coarse crackles
Appearance of malnutrition or low BMI
Nasal polyps
Bilateral absence of the vas deferens in males

Question 14

What is used for screening newborns?

Answer 14

Dried heel prick test

Question 15

How does the dried heel prick test work?

Answer 15

Quantifies serum immunoreactive trypsinogen (IRT)

Question 16

What is done if the skin heel prick test is positive?

Answer 16

Confirmatory sweat test and genetic testing
Refer to CF centre
(Not diagnostic)

Question 17

What is the usual name for the ‘pilocarpine iontophoresis’ test?

Answer 17

Sweat test

Question 18

What are the advantages of the sweat test?

Answer 18

Painless
Relatively inexpensive
Provides results within a few hours
Accutare

Question 19

What does a negative sweat test mean?

Answer 19

Cl <30 mmol/L - CF unlikely but if in doubt refer to CF centre

Question 20

What does a positive sweat test mean?

Answer 20

Cl >60 mmol/L - CF very likely, refer to CF centre

Question 21

What does a sweat test in the indeterminate range mean?

Answer 21

Further investigation and genetic testing may be required

Question 22

What is the genetic testing for cystic fibrosis?

Answer 22

The most common CFTR mutations are screened for and 2 positive CFTR mutations are found

Question 23

What further investigation can be done for cystic fibrosis?

Answer 23

Sinus x-ray

Deep throat swab

Question 24

What is the management for cystic fibrosis with a G551D mutation?

Answer 24

Ivacaftor

Question 25

What is the management for cystic fibrosis with a F508del mutation?

Answer 25

Lumacaftor

Question 26

What is the respiratory management for cystic fibrosis?

Answer 26

Prophylactic antibiotics
Physiotherapy
Bronchodilators
Mucolytics (Dnase)
Annual CXR

Question 27

What antibiotics are used for an exacerbation of pseudomonas, staph aureus and cepacia?

Answer 27

Pseudomonas - ceftazidime
Staph aureus - flucloxacillin
Cepacia - temocillin

Question 28

What is the GI management for cystic fibrosis?

Answer 28

In exocrine pancreatic insufficiency - CREON

In endocrine pancreatic failure - insulin