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Medicine, Year 4, Paediatrics > Immunology > Flashcards

Immunology Flashcards

1
Q

What is the underlying reaction of Anaphylaxis?

A

IgE mediated Type 1 Hypersensitivity reaction

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2
Q

What is the difference between anaphylaxis and an allergic response?

A

Anaphylaxis causes ABC compromise whereas allergy does not

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3
Q

What is the most common cause of anaphylaxis in adults and children?

A

In adults: Drugs

In children: Food

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4
Q

What are some presenting features of Anaphylaxis?

A 
Urticaria
Itching
Angio-oedema
Abdo pain
Stridor
Shortness of breath
Wheeze
Tachycardia
Collapse
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5
Q

Outline the pathophysiology for Anaphylaxis (first vs second exposure)?

A

On first exposure to allergen, there is a sensitisation reaction where IgE antibodies are formed and coats the mast cells and basophils

On second exposure to allergen, these IgE on mast cells and basophils will bind to the antigen and cause degranulation. Degranulation will release inflammatory mediators such as histamine, bradykinin, proteases

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6
Q

What is the difference between anaphylaxis and anaphylactoid reaction?

A

An anaphylactoid reaction results from direct release of inflammatory mediators WITHOUT involving antibodies whereas anaphylactic reactions involve antibodies. There also isn’t a sensitation reaction

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7
Q

Anaphylactoid reactions usually occur in response to what?

A

They tend to be in response to drug exposure

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8
Q

What is “Stridor”?

A

Extrathoracic (above sternal notch) airway obstruction on inspiration

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9
Q

State some common drugs which can cause allergies / anaphylactoid / anaphylactic reactions?

A 
Penicillin
Aspirin
Ibuprofen
Cephalosporins
Anaesthetic agents
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10
Q

What are some risk factors of Anaphylactic reactions?

A
  • Atopy history
  • Previous anaphylaxis
  • Hygiene hypothesis
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11
Q

What conditions are mimics of Anaphylaxis?

A
  • Hereditary angio-oedema
  • Carcinoid tumour
  • Pheochromocytoma
  • Hereditary mastocytosis
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12
Q

Where / how is adrenaline commonly given for anaphylaxis? What is the adult dose? Can it be repeated?

A

IM injection, anterolateral aspect in the middle 1/3rd of the thigh. Dose for adults is 0.5 ml / 500mcg , 1:1,000

Can be repeated after 5 mins

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13
Q

Why might adrenaline be given intravenously? Why is it not routinely given IV?

A

In patients with lost cardiac output, i.e. cardiac arrest

When given IV, can cause side-effects such as arrhythmias

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14
Q

What three medications treat anaphylaxis?

A
  • Adrenaline
  • Chlorphenamine
  • Hydrocortisone
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15
Q

What is the order as to which the three anaphylaxis drugs are given?

A

Adrenaline -> Chlorphenamine -> Hydrocortisone

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16
Q

What is the dose of adrenaline for 6-12 year olds?

A

300 mcg, 1:1,000 IM

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17
Q

What is the dose of adrenaline for 6mo-6 year olds?

A

150 mcg, 1:1,000 IM

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18
Q

What is the dose of adrenaline for <6mo olds?

A

150 mcg, 1:1,000 IM

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19
Q

What is the adult dose of Hydrocortisone for anaphylaxis?

A

200 mg

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20
Q

What is the adult dose of Chlorphenamine for anaphylaxis?

A

10 mg

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21
Q

Patients who have had treatment for anaphylaxis in hospital should be monitored for how long? Why?

A

Atleast 6 hours, due to biphasic reactions

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22
Q

What test definitively confirms anaphylaxis? When should it be taken?

A

Serum tryptase:

  • Measure immediately after treatment
  • Measure 1-2 hours post reaction
  • Measure 24 hours post reaction
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23
Q

Patients with latex allergy are more likely to develop what other allergy?

A

Allergy to fruits: Latex-Fruit Syndrome

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24
Q

What are three trade names for Adrenaline auto-injectors?

A

Epipen
Jext
Emerade

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25
Q

Outline what the “Skin prick test” is?

What is it used for?

A

Used to test food allergies
Diluted food / pollen allergen is placed on skin and pierced with a needle. Wheal should develop in 15mins if positive. There is also a histamine (positive) control and a sterile water (negative) control

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26
Q

Outline what the “Skin patch test” is?

What is it used for?

A

Used to test contact allergies

Multiple allergens are taped to the back, and assessed for contact dermatitis after 48 hours

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27
Q

What is atopy? Give examples of atopic conditions

A

Atopy refers to having hypersensitivity reactions to allergens

Examples include asthma, asthma, hay-fever, allergic rhinitis and food allergies

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28
Q

Give examples of Type 1 Hypersensitivity reactions

A
  • Anaphylaxis

- Atopic conditions

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29
Q

What is the classification to distinguish different types of Hypersensitivites?

A

Gell & Coombs Classification

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30
Q

Outline the mechanism of a Type I Hypersensitivity reaction. What is it aka?

A

Aka anaphylactic:

Antigen reacts with IgE bound to mast cells / basophils

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31
Q

Outline the mechanism of a Type II Hypersensitivity reaction. What is it aka?

A

Aka cell bound:

IgG or IgM binds to antigen on cell surface

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32
Q

Outline the mechanism of a Type III Hypersensitivity reaction. What is it aka?

A

Aka Immune complex

IgG or IgA binds to free antigen

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33
Q

Outline the mechanism of a Type IV Hypersensitivity reaction. What is it aka?

A

Aka Delayed Hypersensitivity

T-cell mediated

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34
Q

What type of Hypersensitivity reaction is Autoimmune Haemolytic Anaemia?

A

II

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35
Q

What type of Hypersensitivity reaction is ITP?

A

II

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36
Q

What type of Hypersensitivity reaction is Serum Sickness?

A

III

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37
Q

What type of Hypersensitivity reaction is Tuberculosis / Tuberculin skin reactions?

A

IV

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38
Q

What type of Hypersensitivity reaction is Systemic Lupus Erythematosus?

A

III

39
Q

What type of Hypersensitivity reaction is Graft vs. Host Disease?

A

IV

40
Q

What type of Hypersensitivity reaction is Allergic Contact Dermatitis?

A

IV

41
Q

What type of Hypersensitivity reaction is PSGN?

A

III

42
Q

What type of Hypersensitivity reaction is Extrinsic Allergic Alveolitis?

A

III

43
Q

What type of Hypersensitivity reaction is Goodpastures?

A

II

44
Q

What type of Hypersensitivity reaction is Rheumatic Fever?

A

II

45
Q

What type of Hypersensitivity reaction is Multiple Sclerosis?

A

IV

46
Q

What type of Hypersensitivity reaction is Guillin-Barre Syndrome?

A

IV

47
Q

What type of Hypersensitivity reaction is Pemphigus Vulgaris and Bullous Pemphigoid?

A

II

48
Q

What is RAST?

How are the results presented?

A

Radioallergosorbent Test (RAST) which detects IgE levels that reacts specifically with suspected or known allergens.

Results are given in grades from 0 (negative) to 6 (strongly positive)

49
Q

What is Allergic Rhinitis?

A

An IgE-mediated Type I Hypersensitivity reaction, where environmental allergens cause inflammation of the nasal mucosa

50
Q

What are the three main types of Allergic Rhinitis?

A
  • Seasonal i.e. hayfever
  • Perennial (year round) i.e. dust mites
  • Occupational
51
Q

What is the presentation for Allergic Rhinitis?

A
  • Runny, blocked, itchy nose
  • Sneezing
  • Post-nasal drip
  • Itchy, red, swollen eyes
52
Q

What are some risk factors for Allergic Rhinitis?

A
  • Personal history of Atopy

- Family history of Atopy

53
Q

How is Allergic Rhinitis diagnosed?

A
  • Clinical diagnosis based on history

- Skin prick test may be useful

54
Q

What is the management for mild-moderate Allergic Rhinitis?

A
  • Avoidance of trigger
  • Oral antihistamines

If anti-histamines fail, then nasal corticosteroids

55
Q

What is the management for moderate-severe Allergic Rhinitis?

A
  • Avoidance of trigger

- Nasal corticosteroids

56
Q

When may oral corticosteroids be indicated in Allergic Rhinitis?

A

To cover important life events

57
Q

Give an example of a topical nasal decongestant

A

Oxymetazoline

58
Q

Why isn’t Oxymetazoline recommended long-term for Allergic Rhinitis?

A
  • Increasing doses will be needed long term, becoming less effective (tachyphylaxis)
  • Withdrawing off can cause rebound nasal hypertrophy (rhinitis medicamentosa)
59
Q

Give 2 examples of sedating anti-histamines

A

Chlorphenamine

Promethazine

60
Q

Give 3 examples of non-sedating anti-histamines

A

Cetrizine
Loratidine
Fexofenadine

61
Q

Give 2 examples of nasal corticosteroids

A

Mometasone

Fluticasone

62
Q

What is a Cow’s Milk Protein Allergy (CMPA)?

A

A condition affecting infants and small children, involving a hypersensitivity to protein in cow’s milk

63
Q

What are the two types of Cow’s Milk Protein Allergy?

A

IgE Mediated - Rapid reaction within 2 hours

Non-IgE Mediated - Reaction over several days

64
Q

What are risk factors to developing Cow’s Milk Protein Allergy?

A
  • Being formula fed
  • Past medical history of Atopy
  • Family history of Atopy
  • Breast fed mothers consuming diary
65
Q

What is the presentation of Cow’s Milk Protein Allergy?

A

GI Symptoms:

  • Bloating / wind
  • Abdominal pain
  • Diarrhoea
  • Vomiting

Allergic symptoms:

  • Urticarial rash
  • Angio-oedema
  • Cough / wheeze
  • Sneezing
  • Watery eyes
  • Eczema
66
Q

How is Cow’s Milk Protein Allergy diagnosed?

A
  • Based on full history and examination

- Skin prick testing may help

67
Q

How is Cow’s Milk Protein Allergy managed?

A
  • Breast feeding mums should avoid dairy
  • Replace formula milk with extensive Hydrolysed Formula (eHF)
  • In severe cases, use Amino Amic based Formula (AAF)
  • Every 6 months try on first step of milk ladder
68
Q

How can Cow’s Milk Protein Allergy and Cow’s Milk Intolerance be differentiated?

A

CMPA: GI and Allergy symptoms (full intolerance)
CMPI: GI symptoms (partial intolerance)

69
Q

What is the prognosis of Cow’s Milk Protein Allergy?

A

The majority of cases (90%) resolve by age 1, the rest by age 2.

70
Q

What is a “Primary Immunodeficiency”?

A

A disorder in which part of the body’s immune system is dysfunctional, and is not due to a secondary cause such as other disease, drugs, toxins

71
Q

State 3 Primary Immunodeficiency B-Cell Disorders

What are B-Cells responsible for?

A
  • Selective IgA Deficiency (IgA Deficiency)
  • Common Variable Immunodeficiency (CVD)
  • Bruton’s (X-linked) Congenital Agammaglobulinaemia (XLA)

B-Cells are responsible for antibody production

72
Q

What is the most common Immunoglobulin Deficiency?

A

Selective IgA Deficiency

73
Q 
In Selective IgA Deficiency, what are the levels of:
IgA
IgM
IgG
IgE
A

IgA - low
IgM - normal
IgG - normal
IgE - may be high (compensatory increase, causing increased risk of atopy / allergic reactions)

74
Q

Where is IgA produced, what is the importance of its role?

A

IgA is produced in the mucous membrane secretions such as saliva, respiratory tract secretions, tears and sweat

It protects against opportunistic infections of these mucous membranes

75
Q

Why is there an increased risk of allergic reactions and atopy with Selective IgA Deficiency?

A

Due to compensatory increase of IgE

76
Q

What is the presentation of Selective IgA Deficiency?

A
  • May be asymptomatic

- May have mild immunodeficiency i.e. recurrent sinus / respiratory tract infections

77
Q

Aside from atopic conditions, what other conditions are associated with Selective IgA Deficiency?

A
  • Autoimmune conditions (Coeliacs, Rheumatoid)

- Gastric / colon cancer

78
Q

In Common Variable Immunodeficiency (CVID), what are the levels of:
IgA
IgG
IgM

What are you at increased risk of?
How is CVID managed?

A

IgA - low
IgG - low
IgM - may be low

Increased risk of auto-immune diseases, bronchiectasis, non-Hodgkin’s lymphoma

Managed with immunoglobulin transfusions

79
Q

What is the inheritance pattern of Bruton’s (X-Linked) Congenital Agammaglobulinaemia?

What are the levels of immunoglobulins?
It is caused by a mutation in what?

A

X-Linked recessive

Reduction in ALL immunoglobulins
Mutation in BTK (Bruton’s Tyrosine Kinase)

80
Q

State 2 Primary Immunodeficiency T-Cell Disorders

A
  • DiGeorge Syndrome

- Purine Nucleotide Phosphorylase Deficiency

81
Q

Outline the genetics / pathophysiology of DiGeorge Syndrome. What is the Catch-22 mnemonic?

A

Microdeletion in chromosome 22, causing a developmental defect in the 3rd pharyngeal pouch / brachial cleft. Causes incomplete development of thymus gland and reduced production of T-Cells

C - Congenital heart disease (ToF)
A - Abnormal facies
T - Thymus gland underdeveloped
C - Cleft palate
H - Hypoparathyroidism / HypoCa2+
22 - 22nd chromosome affected
82
Q

Outline the genetics / pathophysiology of Purine Nucleotide Phosphorylase Deficiency

A

Autosomal recessive, absent PNP enzyme

Absent PNP, dGTP builds up which is toxic to T-Cells.

83
Q

State 3 Primary Immunodeficiency B &T-Cell combined disorders

A

Wiskott-Aldrich Syndrome
Ataxia Telangiectasia
Severe Compromised Immunodeficiency

84
Q

Outline the genetics of Wiskott-Aldrich Syndrome. What are the features of Wiskott-Aldrich Syndrome?

A

X-Linked recessive, characterised by a mutation on the WAS gene. Causes low IgM and T-cells

Features: Thrombocytopenia, Eczema, Recurrent bacterial infections

85
Q

Outline the genetics of Ataxia Telangiectasia. What are the features of Ataxia Telangiectasia?

A

Autosomal recessive, caused by a mutation in the ATM gene

Features: Ataxia, Telangiectasia, Predisposition to cancers i.e. haematological

86
Q

What is the most common mutation associated with SCID?

A

Mutation in the gamma-chain of X-chromosome (X-Linked recessive)

87
Q

What is the management of SCID?

A
  • Immunoglobulin therapy
  • Sterile environment
  • Avoid live vaccines
  • Haematopoetic stem cell transplant
88
Q

What is Omenn Syndrome?
What is it caused by genetically?
What is the inheritance pattern?
What are the features?

A
  • Rare cause of SCID
  • Mutation on RAG1/RAG2 gene
  • Autosomal recessive
  • Erythroderma, alopecia, diarrhoea, lymphadenopathy, hepatosplenomegaly
89
Q

What is the most common Complement deficiency?

A

C2 Deficiency

90
Q

Complement deficiencies lead to an increased susceptibility to infections caused by what?

A

Encapsulated bacterias, i.e. Haemophilus influenzae, Strep pneumoniae, Neisseria meningitidis

91
Q

Hereditary Angiooedema is also known as what?
How can it be treated?
What can be tested to help with diagnosis?

A

C1 Esterase Inhibitor deficiency
Treated by C1 esterase inhibitor
Check C4 levels, will be LOW

92
Q

It is normal for a child to have how many respiratory infections in a year?

A

4-8

93
Q

In a child with recurrent infections which need to be investigated, what investigations might you order?

A
  • Full Blood Count (low neutrophils, low lymphocytes - may suggest phagocytic or T-cell disorder)
  • Immunoglobulins (low, may suggest B cell disorder)
  • Complement proteins (may suggest Complement disorder)
  • Antibody response to vaccinations
  • HIV test
  • CXR (for chest scarring)
  • Sweat test (cystic fibrosis)
  • CT chest (bronchiectasis)

Medicine, Year 4, Paediatrics (16 decks)

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