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Paeds: Respiratory > Cystic fibrosis > Flashcards

Cystic fibrosis Flashcards

1
Q

What is the inheritance pattern of cystic fibrosis?

A

Autosomal recessive

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2
Q

What is the carrier rate and incidence rate of cystic fibrosis?

A

Carrier rate: 1 in 25

Incidence rate: 1 in 2500 live births

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3
Q

What is the trend in life-expectancy in CF?

A

have increased from just a few years to the mid-30s, expected to be into 40s for current newborns

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4
Q

What is the cause of CF in terms of genetics?

A

defective protein called CF transmembrane conductance regulator (CFTR)

this is a cyclic AMP-dependent chloride channel found in the membrane of cells; gene for CFTR located on chromosome 7

over 900 gene mutations discovered that cause distinct defects in CFTR but most frequent in UK is ΔF508

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5
Q

What proportion of cases of CF in the UK are caused by the ΔF508 mutation?

A

78%

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6
Q

On which chromosome is the gene for CFTR located?

A

chromosome 7

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7
Q

What are the effects of the 6 classes of mutation in the CFTR protein? What is the trend as you go down the classes?

A
  1. nonsense/frameshift mutation, no protein synthesised
  2. Incorrect folding: cannot traffic to membrane
  3. Channel opening defect
  4. Pore abnormalities cause decreased conductance
  5. Splicing abnormality - reduced protein synthesis
  6. Shortened half-life of protein

Trend = more CFTR-mediated chloride transport with higher class

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8
Q

What class of CFTR mutation is caused by ΔF508?

A

Class II: incorrect folding, cannot traffic channel to membrane

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9
Q

What are 3 benefits of identifying the gene mutation involved in CF within a family?

A
  1. Prenatal diagnosis
  2. Carrier detection in wider family
  3. Precise genotype now can help guide treatment - CFTR potentiators (Ivacaftor) and CFTR correctors (Lumicaftor)
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10
Q

What are 2 types of drugs that work based on the precise genotype of CF and how do they work?

A
  1. CFTR potentiators e.g. Ivacaftor: restore function of CFTR in class III and IV mutations
  2. CFTR correctors e.g. Lumicaftor: partially restore CFTR number in class II defects
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11
Q

What is an example of a CFTR potentiator?

A

Ivacaftor

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12
Q

What is an example of a CFTR corrector drug?

A

Lumicaftor

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13
Q

What causes the multisystem features of CF in terms of pathophysiology?

A

results from abnormal ion transport across epithelial cells

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14
Q

How does CF cause airway effects?

A
  • In airways, abnormal ion transport across epithelial cells leads to reduction in airway surface liquid layer, and consequent impaired ciliary function and retention of mucopurulent secretions
  • chronic endobronchial infection with specific organisms e.g. Pseudomonas aeruginosa ensues
  • Dysregulated inflammation and defence against infection
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15
Q

What are 4 key examples of organisms which cause chronic endobronchial infection in CF?

A
  1. Staphylococcus aureus (initially)
  2. Haemophilus influenzae (initially)
  3. Pseudomonas aeruginosa
  4. Burkholderia species
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16
Q

What effect can CF have on intestinal function in infants?

A

thick viscid meconium is produced leading to meconium ileus in 10-20% of infants

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17
Q

How does cystic fibrosis affect pancreatic function?

A

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

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18
Q

How does CF affect the sweat?

A

abnormal function of sweat glands leads to excessive concentrations of sodium and chloride in the sweat

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19
Q

How is CF generally diagnosed?

A

all newborn infants born in UK are screened

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20
Q

How does CF screening take place in the newborn?

A

immunoreactive trypsinogen (IRT) is raised in newborn infants with CF, measured in routine heel-prick blood taken for biochemical screening

if samples contain raised immunoreactive trypsinogen, screened for common CF gene mutations, and infants with two mutations have a sweat test to confirm the diagnosis

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21
Q

What are 3 features that some children with CF who are missed by screening may present with?

A
  1. Recurrent chest infections
  2. Faltering growth
  3. Malabsorption
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22
Q

What is the result of chronic chest infection in CF?

A

damage of bronchial wall, bronchiectasis, abscess formation

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23
Q

What are 6 respiratory features of cystic fibrosis with chronic infection on respiratory examination?

A
  1. Persistent ‘wet’ cough, productive of purulent sputum
  2. Hyperinflation of chest due to air trapping
  3. Coarse inspiratory crepitations
  4. Expiratory wheeze
  5. Finger clubbing (if established disease)
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24
Q

What is the biggest killer in CF and what proportion does it affect?

A

Respiratory failure - 95%

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25
Q

What is the key feature of CF in the newborn and what proportion of babies with CF does it affect?

A

Meconium ileus - 10-20%

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26
Q

What causes meconium ileus in the newborn and what are 3 symptoms?

A

inspissated meconium causes intestinal obstruction

  1. Vomiting
  2. Abdominal distension
  3. Failure to pass meconium in the first few days of life
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27
Q

What are 2 options for management of meconium ileus in the newborn?

A
  1. Surgery usually required
  2. Gastrografin enema may relieve obstruction
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28
Q

What is the essential diagnostic procedure for CF and what does it involve?

A
  • Sweat test - to confirm concentration of chloride in sweat is markedly elevted (Cl 60-125mmol/L in CF, normal is 10-40mmol/L)
  • Sweating stimulated by applying low-voltage current to pilocarpine applied to the skin
  • Sweat collected from special capillary tube or absorbed onto weighed piece of filter paper
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29
Q

What is the normal range for chloride ions in sweat and what is it likely to be in CF?

A
  • normal: 10-40mmol/L
  • CF: 60-125mmol/L
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30
Q

What causes frequent diagnostic errors from the sweat test?

A

if inadequate volume of sweat collected

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31
Q

How can a confirmation of a diagnosis of CF be made following the sweat test?

A

testing for gene abnormalities in the CFTR protein

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32
Q

What type of approach is needed to manage CF?

A

multidisciplinary approach

33
Q

How often should patients with CF be reviewed and where?

A

at least annually in specialist centre

34
Q

What is the aim of therapy in CF?

A

prevent progression of lung disease and maintain adequate nutrition and growth

35
Q

What are 8 potential complications of CF to monitor for at reviews?

A
  1. Nasal polyps, sinusitis
  2. Allergic bronchopulmonary aspergillosis (ABPA)
  3. Diabetes mellitus (often insulin-dependent)
  4. Cirrhosis and portal hypertension
  5. Distal intestinal obstruction syndrome (DIOS, meconium ileus equivalent)
  6. Pneumothorax or recurrent haemoptysis
  7. Concern about sterility in males
  8. Rectal prolapse
36
Q

What are 7 things to assess for in terms of respiratory examination at the CF review?

A
  1. Hyperexpansion due to air trapping
  2. Harrison’s sulcus
  3. Coarse inspiratory crepitations and/or expiratory wheeze
  4. Chest infection
  5. Clubbing
  6. Scar from operation for meconium ileus as neonate?
  7. Central venous line e.g. Portacath for IV abx to aggressively treat infection
37
Q

What is a concern regarding salty sweat to ask patients about at their review?

A

may lead to dehydration in hot weather

38
Q

What are 4 things to consider regarding nutrition and growth at the CF review?

A
  1. aiming for normal growth
  2. gastrostomy is option for overnight feeding for extra calories
  3. ensure taking sufficient pancreatic replacement therapy
  4. ensure taking fat soluble vitamins
39
Q

What are 7 aspects of management of chest problems in CF to review?

A
  1. Spirometry - to identify deterioration
  2. Regular breathing exercises?
  3. Physiotherapy and exercise?
  4. Bronchodilator therapy - is it optimal?
  5. Chest infection - acute or chronic and its treatment?
  6. Nebulised antipseudomonal antibiotics and DNase?
  7. Avoidance of direct contact with other affected patients other than family members?
40
Q

What are 3 things to consider as part of a general overview at a CF review appointment?

A
  1. School attendance and performance
  2. Specific problems with managing their disease
  3. Psychological needs
41
Q

Overall, what are 8 parts of the review appointment for CF to remember?

A
  1. Chest examination
  2. Monitor for potential complications
  3. Sputum - acute or chronic colonisation?
  4. Nutrition + growth
  5. Review of chest problems
  6. General overview
  7. Dehydration due to salty sweat
  8. Siblings affected?
42
Q

What is the major respiratory problem in CF?

A

recurrent and persistent bacterial chest infection

43
Q

What are 2 ways that respiratory monitoring is performed in children and what does this depend on?

A
  1. Older children: lung function measured regularly by spirometry
  2. Younger children: symptoms
44
Q

How is spirometry used to determine lung function in older children with CF?

A

FEV1 expressed as a percentage of predicted for age, sex and height is indicator of clinical severity, and declines with disease progression

45
Q

What role does physiotherapy for respiratory management of CF and when is this introduced?

A
  • introduced from diagnosis, should have physiotherapy at least twice a day.
  • in younger children, parents taught to perform airway clearance at home using chest percussion and postural drainage
  • older patients perform controlled deep breathing exercises and use variety of physiotherapy devices for airway clearance
  • physical exercise beneficial and encouraged
46
Q

What treatment for recurrent and persistent chest infections is available for CF?

A
  • many specialists recommend continuous prophylactic oral antbiotics, usually flucloxacillin, with additional rescue oral antibiotics for increases in respiratory symptoms or decline in lung function
  • persisting symptoms or signs require prompt and vigorous IV therapy to limit lung damage, usually 14 days via PIC (peripherally inserted central) line
47
Q

What is the treatment for persisting new symptoms or signs of chest infection in CF that aren’t cleared with rescue oral antibiotics?

A

Prompt and vigorous IV therapy, usually for 14 days via PIC (peripherally inserted central) line

Parents increasingly taught to administer IV abx at home to decrease school/acitivity disruption

48
Q

Which type of infection is associated with a more rapid decline in lung function in cystic fibrosis?

A

Pseudomonas auruginosa

49
Q

How can the rapid decline in lung function due to Pseudomonas infection be slowed?

A

daily nebulised antipseudomonal antibiotics

50
Q

What are 2 therapies available to decrease viscosity of sputum and increase its clearance in CF?

A
  1. Nebulised DNase
  2. Hypertonic saline
51
Q

What are 2 treatments that can be given in CF to reduce respiratory exacerbations?

A
  1. Regular nebulised hypertonic saline
  2. Macrolide antibiotic azithromycin
52
Q

What can be done for more severe CF requiring regular IV abx when venous access becomes troublesome?

A

Implantation of central venous catheter with subcutaneous acess port e.g. Portacath - simplified access

53
Q

What are the issues with inserting a central venous catheter e..g Portacath for regular IV abx therapy in CF?

A

require monthly flushing, complications may develop

54
Q

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

A

bilateral sequential lung transplantation

55
Q

What is the current survival rate following bilteral lung transplant for CF?

A

50% survival at 10 years - continues to increase

56
Q

What proportion of children with CF have pancreatic exocrine insufficiency?

A

over 90%

57
Q

What are the 3 types of enzymes that are deficient in pancreatic exocrine insufficiency?

A

lipase

amylase

proteases

58
Q

What does pancreatic enzyme insufficiency result in?

A

maldigestion and malabsorption - this leads to faltering growth if untreated, with frequent large, pale and greasy stools (steatorrhoea)

59
Q

How can pancreatic insufficiency be diagnosed in CF?

A

demonstrated low faecal elastase

60
Q

What are 4 aspects of nutritional management in CF?

A
  1. Dietary status should be assessed regularly
  2. Pancreatic insufficiency treated with oral enteric-coated pancreatic replacement therapy - take with all meals and snacks
  3. High calorie diet essential - 150% dietary intake, overnight gastrostomy
  4. Fat-soluble vitamin supplements
61
Q

Why do CF patients require supplementation of fat-soluble vitamins?

A

difficuly absorbing fats due to pancreatic enzyme insufficiency - leads to malabsorption of fat-soluble vitamins

62
Q

What determines dosage of oral pancreatic replacement therapy?

A

taken with all meals and snacks

dosage adjusted according to clinical response

63
Q

What are 2 ways that a high-calorie diet can be achieved in CF?

A
  1. Dietary intake recommended at 150% of normal
  2. Overnight feeding via gastrostomy increasingly used
64
Q

What is the most common complication of CF as patients grow into adult life?

A

diabetes mellitus - due to decreased pancreatic endocrine function

65
Q

What proportion of CF patients have evidence of liver disease, and what possible clinical presentations of this?

A

up to a third

  1. Hepatomegaly on palpation
  2. Abnormal liver function on blood tests
  3. Abnormal ultrasound
66
Q

How can early liver disease in CF be managed?

A

regular ursodeoxyholic acid to improve flow of bile may be beneficial

67
Q

What can liver disease progress to in CF in rare instances and how is this managed?

A

Cirrhosis, portal hypertension, and ultimately liver failure

Liver transplant very successful

68
Q

What is distal intestinal obstruction syndrome (DIOS)?

A

meconium ileus equivalent: viscid mucofaeculent material obstructs the bowel

69
Q

How can distal intestinal obstruction syndrome be treated?

A

usually cleared by combination of oral laxative agents

70
Q

What are 2 late respiratory complications of CF?

A
  1. Pneumothorax
  2. Life-threatening haemoptysis
71
Q

What is one behavioural measure to reduce incidence of chest infections in CF and why?

A

segregated CF patients, advised not to socialise with other people with CF - as increasing concern over transmission of virulent strains of Pseudomonas and Burkholderia cepacia

72
Q

How is fertility affected in females?

A

usually normal, unless severe lung disease can tolerate pregnancy well

73
Q

How is fertility affected in males in CF?

A

virtually always infertile due to absence of vas deferens, but can father chidlren through intracytoplasmic sperm injection

74
Q

What psychological support is provided in CF?

A

psychological and emotional support provided to children and families as chronic and ultimately fatal illness; adolescents have particular needs which must receive special consideration

older adolescents should transfer to specialist adult CF care

75
Q

What hopes for the future treatment of CF are there, and what is the current limitation?

A

CFTR potentiators and CFTR correctors may significantly improve outcomes

Availability limited by high cost

76
Q

What are 4 features of CF in infancy?

A
  1. Prolonged neonatal jaundice
  2. Growth faltering
  3. Recurrent chest infections
  4. Malabsorption, steatorrhoea
77
Q

What are 4 features of CF in the young child?

A
  1. Bronchiectasis
  2. Rectal prolapse
  3. Nasal polyp
  4. Sinusitis
78
Q

What are 6 possible features of CF in the older child and adolescent?

A
  1. Allergic bronchopulmonary aspergillosis (ABPA)
  2. Diabetes mellitus
  3. Cirrhosis and portal hypertension
  4. Distal intestinal obstruction syndrome (DIOS)
  5. Pneumothorax or recurrent haemoptysis
  6. Sterility in males

Paeds: Respiratory (7 decks)

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