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Paediatrics > Respiratory: Cystic Fibrosis > Flashcards

Respiratory: Cystic Fibrosis Flashcards

1
Q

What type of inheritance pattern does CF have?

A

Autosomal recessive

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2
Q

Which gene is defective?

A

The CF transmembrane conductance regulator gene (CFTR) = a cyclic AMP dependent chloride channel found in the membrane of cells

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3
Q

The gene for CFTR is located on chromosome..

A

7

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4
Q

What is the most frequent mutation of the CFTR gene?

A 
DeltaF508 (this protein is misfolded and cannot migrate from the endoplasmic reticulum to the cell membrane - lack of CFTR on epithelial surface)
A class II mutation
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5
Q

CF is the most common life limiting autosomal recessive condition in Caucasians. True or false?

A

True

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6
Q

What is the incidence rate?

A

1 in 2500 live births

Carrier rate of 1 in 25

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7
Q

What is the life expectancy for current newborns?

A

Into the 40s

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8
Q

Describe the pathophysiology

A

Abnormal ion transport occurs across epithelial cells, causing increased viscosity of secretions.
The CTFR channel protein pumps chloride ions into secretions. The chloride ions help draw water into the secretions, thinning them out.

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9
Q

Is CF a multi system disorder?

A

Yes

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10
Q

How are newborns affected?

A

In the intestines, thick viscous meconium is produced leading to meconium ileus in 10-20% of infants

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11
Q

How can the pancreas be affected?

A

The pancreatic ducts become blocked by thick secretions, leading to pancreatic enzyme insufficiency and malabsorption

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12
Q

Without pancreatic enzymes, what is not absorbed?

A

Protein and fat

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13
Q

What can fat malabsorption lead to?

A

Steatorrhoea (fat containing stools)

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14
Q

Why can the pancreas become damaged?

A

The trapped enzymes degrade the cells that line the ducts - local inflammation and acute pancreatitis. With repeated episodes = chronic pancreatitis with development of cysts and fibrosis

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15
Q

Pancreatic damage can cause endocrine dysfunction and lead to…

A

Insulin dependent diabetes

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16
Q

Why do recurrent chest infections occur?

A

The thickened mucus in the airways impairs ciliary function. Consequently there is retention of mucopurulent secretions - this facilitates bacterial overgrowth

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17
Q

What bacteria typically cause the chest infections?

A

Staphylococcus aureus
Haemophilius influenzae
Pseudomonas aeruginosa
Burkholderia cepacia

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18
Q

What respiratory signs and symptoms can occur?

A

Persistent wet cough
Purulent sputum production
Hyperinflation of chest due to air trapping
Coarse inspiratory crepitations and/or expiratory wheeze
With established disease: finger clubbing

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19
Q

Chronic lung infections can lead to…

A

Damage to bronchial wall, bronchiectasis, abscess formation

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20
Q

What is the leading cause of death with CF?

A

Respiratory failure

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21
Q

What is bronchiectasis?

A

Airway wall damage causing permanent dilation of the bronchi

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22
Q

Over what percentage of children with CF have pancreatic exocrine insufficiency? (Lipase, amylase, proteases)

A

90%

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23
Q

Pancreatic exocrine insufficiency leads to…

A

Maldigestion and malabsorption. Untreated this leads to faltering growth

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24
Q

How can pancreatic insufficiency be diagnosed?

A

Demonstrating low faecal elastase

Faecal elastase is not degraded after secretion - a way to measure pancreas’ exocrine function

25
Q

Why is there infertility in men?

A

They lack the vas deferens - carries sperm from testes to urthera in penis

26
Q

Other than recurrent chest infections, what other respiratory conditions can occur?

A 
Bronchiectasis
Nasal polyps
Sinusitis 
Allergic bronchopulmonary aspergillosis (ABPA) 
Pneumothorax
27
Q

What is allergic bronchopulmonary aspergillosis?

A

A hypersensitivity reaction to aspergillus fumigatus - growth within a sinus or lung cavity provokes an IgE mediated response, causing airway inflammation, bronchospasm, bronchiectasis

28
Q

About 10-20% of infants with CF present in neonatal period with meconium ileus causing intestinal obstruction. Typically this presents as…

A

Vomiting
Abdominal distension
Failure to pass meconium in first few days of life

29
Q

How is meconium ileus treated?

A

Usually surgery

Gastrografin enema may relive obstruction

30
Q

How is the meconium usually passed in the stools?

A

Usually at birth the meconium (made up of bile, mucus, amniotic fluid, water) is broken down by pancreatic enzymes and is passed in the stools.

31
Q

What features of CF are typically seen as a newborn?

A

Meconium ileus

Neonatal jaundice

32
Q

What features are seen in infancy?

A

Growth faltering
Recurrent chest infections
Malabsorption, steatorrhoea

33
Q

What features are seen in young children?

A

Bronchiectasis
Rectal prolapse
Nasal polyps
Sinusitis

34
Q

What features are seen in older children?

A 
ABPA
DM
Cirrhosis and portal hypertension
Distal intestinal obstruction 
Pneumothorax or recurrent haemoptysis
Sterility in males
35
Q

Is there a screening test?

A

Yes, all newborn infants in UK screened for CF

Reduces diagnostic delay

36
Q

How is screening done?

A

Heel prick test - immunoreactive trypsinogen (IRT) raised in newborn infants with CF
Samples with raised IRF are screened for common CF gene mutations and infants with 2 mutations have a sweat test to confirm diagnosis

37
Q

How is CF diagnosis confirmed?

A

Sweat test - to confirm the concentration of chloride in sweat (it is markedly elevated: 60-125mmol/L in CF, in normal children = 10-40)

38
Q

Diagnostic errors in the sweat test are common if…

A

There is an inadequate volume of sweat collected

39
Q

What is involved in the sweat test?

A

Sweating stimulated by applying low current to pilocarpine applied to skin - sweat collected into capillary tube or absorbed onto filter paper. Concentration of sodium and chloride measured - it is the chloride that is important for diagnosis

40
Q

Why is chloride raised in the sweat test in those with CF?

A

The defective / absent CFTR protein does not reabsorb chloride into the sweat duct - remains on the skin surface

41
Q

What is another term for the IRT test?

A

Guthrie test

42
Q

What other test, not performed for diagnosis, are likely to be abnormal?

A

Raised GGT
Vitamins A,D,E,K low (fat soluble) - lost in steatorrhoea
CXR - hyperinflation, bronchiectasis
Abdominal USS - fatty liver, cirrhosis, chronic pancreatitis
Spirometry - obstructive pattern

43
Q

What is the aim of therapy?

A

Prevent progression of lung disease

Maintain adequate nutrition and growth

44
Q

The effective management of CF requires a …

A

MDT approach

At least annual review in a specialist centre

45
Q

Describe respiratory management

A

From diagnosis: physiotherapy at least twice per day, aiming to clear airways and secretions
In younger children, parents taught to perform airway clearance at home using chest percussion and postural drainage
Older patients - controlled deep breathing exercises
Physical exercise beneficial and encouraged
Many CF specialists recommend continuous prophylactic oral antibiotics (usually flucloxacillin) with additional rescue antibiotics for increase in symptoms
Persisting symptoms: IV therapy to limit lung damage - usually 14 days via PIC

46
Q

Chronic pseudomonas infection is associated with a more rapid decline in lung function, which is slowed by daily use of …

A

Nebulised antipseudomonal antibiotics

47
Q

What can be used to help decrease the viscosity of respiratory secretions?

A

Nebulised DNase or hypertonic saline

48
Q

If venous access becomes difficult, what can be done?

A

Implantation of central venous catheter with a port

49
Q

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

A

Bilateral sequential lung transplantation - over 50% survival at 10 years

50
Q

Describe the nutritional management

A

Dietary status assessed regularly
Oral pancreatic enzyme supplements taken with all meals and snacks
High calorie diet including high fat intake
Dietary intake recommended at 150% normal - overnight feeding via gastrostomy may be needed
Fat soluble vitamin supplements

51
Q

What can be used to treat CF patients who are homozygous for the delay F508 mutation and how does it work?

A

Lumicaftor - a CFTR corrector

Partially restore CFTR numbers - increasing numbers of the protein transported to cell surface

52
Q

What is ivacaftor?

A

A CFTR potentiator - increases they probability that the defective channel will be open and allow chloride ions to pass through the channel

53
Q

What percentage of adolescents with have evidence of liver disease, with hepatomegaly on palpation, abnormal LFTs and abnormal USS ?

A

Up to 1/3

54
Q

What can be given to help improve bile flow?

A

Ursodeoxycholic acid

55
Q

Is it rare for the liver disease to progress to cirrhosis, portal hypertension and liver failure?

A

Yes

But liver transplant is generally very successful in CF related liver failure

56
Q

If viscous material obstructs the bowel, how can it be cleared?

A

A combination of oral laxative agents

57
Q

Why is it advised that patients with CF should minimise contact with each other?

A

To prevent cross infection with virulent strains of pseudomonas aeruginosa and Burkholderia cepacia causing rapid decline in lung function

58
Q

In younger patients, respiratory monitoring is based on..

A

Symptoms

59
Q

Older children should have their lung function measured regularly by…

A

Spirometry

The FEV1 is an indicator for clinical severity

Paediatrics (104 decks)

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