Cystic Fibrosis

Question 1

What is the primary cause of cystic fibrosis?

Answer 1

A defect in the gene that codes for the cystic fibrosis trans-membrane conductance regulator

Question 2

How does the CFTR cholrine channel normally function?

Answer 2

The CFTR channel pumps cholride ions out of epithelial cells

The activation of the channel allows the functioning of surrounding chloride channels

The sodium transporter is inhibited meaning sodium cannot enter cells

This means osmosis will be directed outwards into the airways keeping them moist

Question 3

How does a CFTR mutation cause cystic fibrosis in the airways?

Answer 3

Cholrine cannot be transported across the cell membrane via the CFR channel or the surrounding cholide channels which canow now not be activated

Inhibition of the sodium ion transporter ceases

Sodium enters the cell reversing the osmotic gradient into the cell

This dries out the aiwards creating very thick sputum

Question 4

What is the most common mutation in cystic fibrosis?

Answer 4

Deletion of phenylalanine at position 508

Question 5

What is a promising therapy for cystic fibrosis?

Answer 5

Lumacaftor

Question 6

How is cystic fibrosis treated if infected with staph aureus?

Answer 6

Oral flucloxacillin
and tigecycline

Oral septrin

Question 7

How is cystic fibrosis treated if infected with pseudomonas?

Answer 7

• Oral azithromycin
• Nebulised colomycin
• Nebulised or inhaled tobramycin
• Nebulised aztreonam

Question 8

Cystic fibrosis affects the lungs, but which other parts of the body are affected?

Answer 8

• Pancreas
• Bowels
• Liver

Question 9

How does cystic fibrosis affect the exocrine function of the pancreas?

Answer 9

Pancreatic ducts are blocked and lipases and amylase cannot be secreted

Digestive failure occurs

Question 10

How can the exocrine functioning of the liver be treated when cystic fibrosis is present?

Answer 10

CREON

(pancrelipase)

Question 11

How does cystic fibrosis affect pancreatic endocrine function?

Answer 11

Pancreatic islet cells are destroyed and replaced with fatty tissue

This can cause diabetes and insulin needs to be administered

Question 12

How can the bowels be affected by cystic fibrosis?

Answer 12

Distal intestinal obstruction syndrome

Mucus blocks the small and large intestines

Question 13

How is distal intestinal obstruction syndrome (DIOS) treated?

Answer 13

Additional fluids

Gastrografin - a contrast medium to locate areas of blockage

Laxido (laxiative)

Question 14

How can the liver be affected by cystic fibrosis?

Answer 14

Hepatic ducts become blocked

This can lead to portal hypertension causing variceal bleeding

Question 15

What is hepatic encephalopathy?

Answer 15

A decrease in brain function due to brain damage by a build up in toxins the liver fails to remove

Question 16

Why should antibiotics always be used in pairs?

Answer 16

Reduced instance of resistance

Question 17

What is the best investigation to diagnose cystic fibrosis in adults?

Answer 17

Sweat test

Question 18

Cystic fibrosis

Question: Neonatal features

Answer 18

Failure to thrive

Meconium Ileus

Rectal prolapse

Question 19

Cystic fibrosis patients colonised with a which bacterium should avoid cystic fibrosis patients without this bacterium?

Answer 19

Burkholderia cepacia

Question 20

Cystic fibrosis

Question: Medical Management

Answer 20

Infective exacerbations are treated with:

antibiotics, although for patients with recurrent chest infections prophylactic long-term antibiotics may be prescribed.

Nebulised mucolytics (Dornase Alfa)

Bronchodilators (Inhaled corticosteroids or B2-agonists)

Pancreatic insufficiency is treated with:

Insulin replacement regime

Exocrine enzymatic replacement (Creon)

Vitamin A, D, E, K

Abnormal liver function/ deranged liver function tests are treated with:

Ursodeoxycholic acid
Worsening progressive lung disease is treated with:

Oxygen

Non invasive ventilation

Diuretics if signs of cor pulmonale

Question 21

What are potential complications of infection with Campylobacter jejuni?

Answer 21

Guillain-Barre Syndrome
Reactive arthritis

Question 22

Which investigations are indicated in suspected lung cancer?

Answer 22

Sputum cytology
Chest X-ray: Abnormalities that may be seen include nodules, lung collapse, pleural effusion, consolidation, and bony metastases.
Contrast enhanced CT scan: This is used to further confirm the diagnosis and stage (TNM classification) the disease. The CT scan should also include both the adrenals and liver to look for sites of metastases.
Bronchoscopy: Used to obtain a sample for histology
Endobronchial Ultrasound transbronchial needle aspiration (EBUS-TBNA): allows biopsy of lymph nodes, paratracheal and bronchial lung lesions for histology

Question 23

ystic fibrosis

Question: Investigations in patients with Cystic Fibrosis

Answer 23

Known Cystic Fibrosis

Investigations performed for patients with CF encompass looking for the cause of symptoms, in addition to investigating complications of the condition. They can also be conducted to monitor disease progress and severity.

Bedside Tests:

Sputum culture or throat swab: if a patient presented with symptoms indicative of respiratory tract infection.

Blood: Full Blood Count; Urea and Electrolytes; Liver Function Tests; Clotting studies; Vitamin A, D, E, K and Glucose levels

Glucose tolerance test (to identify diabetes mellitus)

Spirometry: obstructive defect

Aspergillus skin prick test or serology

Radiological Imaging:

Abdominal ultrasound: Distal Intestinal Obstruction; liver cirrhosis; chronic pancreatitis

Chest X-ray: Hyperinflation, bronchiectasis

Question 24

hat is the cause of Cystic Fibrosis?

Answer 24

A mutation in the cystic fibrosis transmembrane conductance regulator protein (CFTR), a sodium channel that is involved in the production of sweat, gastrointestinal fluids and mucus.

Question 25

What test do babies have as part of their newborn screening to test for nine serious diseases including cystic fibrosis?

Answer 25

Heel-prick test

Question 26

Cystic fibrosis

Question: Gastrointestinal features

Answer 26

Pancreatic insufficiency resulting in diabetes mellitus and steatorrhea

Cirrhosis

Portal hypertension

Gallstones

Distal Intestinal Obstruction Syndrome

Question 27

What is the screening test for cystic fibrosis?

Answer 27

Sweat test
Immunoreactive trypsin levels (effective in neonates <8 weeks old)

Question 28

Which annual vaccine is recommended for patients with cystic fibrosis?

Answer 28

Influenza

Question 29

What are the extra pulmonary features of cystic fibrosis?

Answer 29

GI – pancreatic exocrine insufficiency leading to malabsorption of macronutrients and fat soluble vitamins (A, D, E, K). Higher risk of intussusception, constipation and intestinal obstruction. Endocrine – pancreatic endocrine insufficiency leading to diabetics mellitus. Poor uptake of vitamin D leads to dysregulated calcium homeostasis and osteoporosis. Infertility – Most men with cystic fibrosis are infertile due to a congenital absence of the vas deferens. Some women have difficulty reproducing due to thickened cervical mucus and disrupted ovulation due to poor nutrition

Question 30

Topic: Cystic fibrosis

Question: Respiratory features

Answer 30

Chronic Sinusitis

Nasal Polyps

Symptoms including cough, wheeze, haemoptysis

Recurrent lower respiratory tract infections

Bronchiectasis

Pneumothorax

Cor pulmonale

Respiratory failure

Question 31

Question 16
What is the most common mutation that causes cystic fibrosis?

Answer 31

The delta F508 mutation that codes for the cystic fibrosis transmembrane conductance regulator (CFTR) protein is most commonly implicated

Question 32

What is the pattern of inheritance of cystic fibrosis?

Answer 32

Autosomal recessive

Question 33

Which electrolyte is transported by the transmembrane conductance regulator (CTFR) gene?

Answer 33

Chloride