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Paediatrics > Paediatrics Immunology > Flashcards

Paediatrics Immunology Flashcards

1
Q

What is allergy?

A

Umbrella term for hypersensitivy of the immune system to allergens​ (proteins that the immune sysem recognises as foreign and potentially harmful)

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2
Q

What is atopy?

A

Term for predisposition to having hypersensitivity reactions to allergens

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3
Q

What conditions does atopy encompass?

A

Eczema

Asthma

Hayfever

Allergic rhinitis

Food allergies

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4
Q

What is the skin sensitisation theory of allergy?

A
  • Break in the infants skin (from eczema or a skin infection) allowing allergens e.g. peanut proteins into body and react with immune system
  • Child does not have contact with allergen from GI tract and absence of GI exposure next time its encountered its recognised as foreign
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5
Q

What classification system is used for hypersensitivity reactions?

A

Coombs and Gell classification

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6
Q

What is a type 1 hypersensitivity reaction?

A

Immediate reaction with IgE antibodies a specific allergen triggers mast cells and basophils to release histamines and other cytokines

Typical food allergy reaction (= itching, facial swelling, urticaria, anaphylaxis)

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7
Q

What is a type 2 hypersensitivity reaction?

A

IgG and IgM antibodes react to an allergen and activate the complement system causing direct damage to local cells e.g. haemolytic disease of the newborn and transfusion reactions

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8
Q

What is a type 3 hypersensitivity reaction?

A

Immune complexes accumulate and cause damage to local tissues e.g. systemic lupus erythematosus (SLE) rheumatoid arthritis and Henoch-Schonlein purpura (HSP)

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9
Q

What is a type 4 hypersensitivity reaction?

A

Cell mediated hypersensitivity reaction caused by T lymphocytes - inappropriately activated - causing inflammation and damage to local tissues e.g. organ transplant rejection and contact dermatitis

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10
Q

How are allergies diagnosed?

A

History

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11
Q

What to cover in allergy history?

A

Timing after exposure to allergen

Previous and subsequent exposure and reaction to allergen

Symptoms of rash, swelling, breathing difficulty, wheezeand cough

Previous personal / FH of atopy

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12
Q

What are the 3 ways to test for allergy?

A

Skin prick testing

RAST testing - blood tests for total and specific immunoglobulin E (IgE)

Food challenge testing

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13
Q

What are skin prick testing and RAST testing assessing?

A

Sensitisation and not allergy (makes these tests notoriously unreliable and misleading)

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14
Q

What is the gold standard for diagnosing allergy?

A

Food challenge testing (requires lots of time and resources)

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15
Q

How is skin prick testing performed?

A

Allergens e.g. peanuts, house dust mite and pollen are dropped onto marked points on forearm along with water control and histamine control fresh needle is used to make a tiny break in the skin at each site - after 15 mins the size of the wheals to each allergen are assessed and compared

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16
Q

What testing is used to assess allergic contact dermatitis?

A

Patch testing

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17
Q

How is patch testing performed?

A

Patch containing allergen is placed on patients skin (either a specific allergen or grid of lots of allergens)

After 2-3 days the skin reaction to the patch is assessed

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18
Q

What is RAST testing?

A

Measures total and allergen specific IgE quantities in patients blood

In patients with atopic conditions e.g. eczema and asthma - results will often come back positive for everything you test

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19
Q

How is a food challenge performed?

A

In specialised unit with close monitoring

Child is given increasing quantities of an allergen to assess the reaction

Can be helpful in excluding allergies for reassurance

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20
Q

What is the management of allergy?

A

Establishing correct allergen

Avoidance of allergen

If allergic to dust mites then regular hoovering and changing sheets

Staying in doors when pollen count is high

Prophylactic antihistamines when contact is inveitable e.g. hayfever and allergic rhinitis

Given adrenalin auto-injector

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21
Q

What is immunotherapy?

A

Gradually exposing patient to allergens over months with aim of reducing their reaction

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22
Q

What is the treatment of allergic reactions?

A

Antihistamines (e.g. cetirizine)

Steroids (e.g. oral prednisolone, topical hydrocotrisone or IV hydrocortisone)

IM adrenalin in anaphylaxis

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23
Q

How do antihistamines and steroids work?

A

Dampening the immune response to allergens

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24
Q

What is anaphylaxis?

A

Life-threatening emergency

Severe type 1 hypersensitivity reaction

IgE stimulates mast cells to rapidly release histamine (mast cell degranulation) causing airway, breathing and/or circulation compromise

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25
Q

How to differentiate anaphylaxis from non-anaphylactic allergic reaction?

A

Compromise of the airway, breathing or circulation

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26
Q

How does anaphylaxis present?

A

Urticaria

Itching

Angio-oedema with swelling around the lips and eyes

Abdo pain

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27
Q

Which additional symptoms indicate anaphylaxis?

A

SoB

Wheeze

Swelling of larynx causing stridor

Tachycardia

Lightheadedness

Collapse

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28
Q

What is the initial management of anaphylaxis?

A

A – Airway: Secure the airway

B – Breathing: Provide oxygen if required. Salbutamol can help with wheezing.

C – Circulation: Provide an IV bolus of fluids

D – Disability: Lie the patient flat to improve cerebral perfusion

E – Exposure: Look for flushing, urticaria and angio-oedema

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29
Q

What medications to give during anaphylaxis?

A

IM adrenalin (repeated after 5 minutes if required)

Antihistamines e.g. chlorphenamine or cetirizine

Steroids usually IV hydrocortisone

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30
Q

What is the management after anaphylaxis?

A

Period of assessment and observation as biphasic reactions can occur (admission to paediatric unit)

Confirm anaphylaxis with serum mast cell tryptase within 6 hours of the event (tryptase is released during mast cell degranulation)

Education and follow-up of family and child - educated about allergy, how to avoid and how to spot signs of anaphylaxis

Train patients in BLS

Train patients in using adrenalin auto-injector

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31
Q

What are the adrenalin auto-injector trade names?

A

Epipen

Jext

Emerade

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32
Q

When are adrenalin auto-injectors indicated?

A

Asthma requiring inhaled steroids

Poor access to medical treatment (e.g. rural locations)

Adolescents who are at higher risk

Nut or insect sting allergies are higher risk

Co-morbidities e.g. CVD

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33
Q

How is the adrenlin auto-injector used?

A

Confirm the diagnosis of anaphylaxis

Remove cap on non-needle end

Grip device with needle end pointing downwards

Administer injection (hold in place)

Remove device and gently massage area for 10 seconds

Phone an ambulance

Second dose may be given after 5 mins if required

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34
Q

What is allergic rhinitis?

A

Condition caused by an IgE-mediated type 1 hypersensitivity reaction

Environmental allergens cause an allergic inflammatory response in the nasal mucosa - very common and can significantly affect sleep, mood, hobbies, work and school performance and quality of life

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35
Q

What may the pattern of allergic rhinitis be?

A

Seasonal e.g. hay fever

Perennial (year round) e.g. house dust mite allergy

Occupational associated with school / work environment

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36
Q

How may allergic rhinitis present?

A

Runny, blocked and itchy nose

Sneezing

Itchy, red and swollen eyes

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37
Q

How is allergic rhinitis diagnosed?

A

Made on the history

Skin prick testing can be useful particularly testing for pollen, animals and house dust mite allergy

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38
Q

What are the triggers for allergic rhinitis?

A

Tree pollen or grass leads to seasonal symptoms (hay fever)

House dust mites and pets can cause persistent symptoms, often worse in dusty rooms at night - pillows can be full of house dust mites

Pets can lead to persistent symptoms when the pet or their hair, skin or saliva is present

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39
Q

What is the management of allergic rhinitis?

A

Avoid trigger

Hovering / changing pillows / allowing good ventilation of the home

Stay indoors during high pollen count

Minimise contact with pets known to trigger allergies

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40
Q

What is the medication for allergic rhinitis?

A

Oral antihistamines taken prior to exposure to reduce allergic symptoms

  • non-sedating antihistamines e.g. cetirizine, loratadine and fexofenadine
  • sedating antihistamines including chlorphenamine (Piriton) and promethazine

Nasal corticosteroid sprays e.g. fluticasone and mometasone used regularly to suppress local allergic symptoms

Nasal antihistamines could be a good option for rapid onset symptoms in response to a trigger

41
Q

What is good nasal spray technique?

A

Aim to coat the nasal passage

Hold spray in left hand when spraying into right nostril and vice versa

Spray outwards - away from septum

DON’T sniff at the same time (should not taste spray at back of mouth)

42
Q

What is cow’s milk protein allergy?

A

Hypersensitivity to protein in cow’s milk

If IgE mediated then rapid reaction to cows milk (within 2 hours)

Non-IgE mediated where reactions are slow over several days

43
Q

Who does cow’s milk protein allergy affect?

A

Condition affecting infants and young children under 3 years

44
Q

How is cow’s milk protein intolerance different to lactose intolerance or cow’s milk intolerance?

A

There is no allergy to lactose in cow’s milk protein intolerance (lactose is a sugar)

Cow’s milk intolerance is not an allergic process - doesn’t involve the immune system

45
Q

When is cow’s milk protein allergy more common?

A

Formula fed babies

FH or atopy

46
Q

When does cow’s milk protein intolerance become apparant?

A

When weaned from breast milk or breast fed babies when mother is consuming dairy products

47
Q

What are the GI symptoms of cow’s milk protein intolerance?

A

Bloating and wind

Abdo pain

Diarrhoea

Vomiting

48
Q

What are the allergic symptoms in response to cow’s milk protein?

A

Urticarial rash (hives)

Angio-oedema (facial swelling)

Cough / wheeze

Sneezing

Watery eyes

Eczema

49
Q

How is cow’s milk protein intolerance diagnosed?

A

Full history and examination

Skin prick testing can help support diagnosis

50
Q

What is the management of cow’s milk protein intolerance?

A

Avoid cow’s milk

If breast feeding then avoid dairy products

Replace formula with special hydrolysed formulas designed for cow’s milk allergy

51
Q

What are hydrolysed formulas?

A

Contain cow’s milk, however proteins have been broken down so they no longer trigger an immune response (severe causes require elemental formulas made from basic amino acids e.g. neocate)

52
Q

How does cow’s milk protein intolerance progress?

A

Most outgrow allergy by age 3

Every 6 months or so tried on the milk ladder (e.g. malted milk biscuits) then slowly progress up the ladder

53
Q

How does cow’s milk intolerance present?

A

Same GI symptoms as cow’s milk allergy:

  • Bloating
  • Wind
  • Diarrhoea
  • Vomiting

No allergic features (e.g. rash, angio-oedema, sneezing and coughing)

54
Q

How is cow’s milk intolerence managed?

A

Grow out of it by 2-3 years

Fed with breast milk, hydrolysed formulas and weaned to foods not containing cow’s milk

After one year can be started on milk ladder

55
Q

How many respiratory infections are normal for a child in a year?

A

4-8

56
Q

When should children with recurrent infection be investigated?

A

Chronic diarrhoea since infancy

Failure to thrive

Appearing unusually well with a severe infection e.g. afebrile with a large pneumonia

Significantly more infections than expected e.g. bacterial lower respiratory tract infections

Unusual or persistent infections e.g. cytomegalovirus, candida and pneumocystis jiroveci

57
Q

What are the choice of investigations for recurrent infection in childhood?

A

FBC: low neutrophils = phagocytic disorder

low lymphcytes = T cell disorder

Immunoglobulins: abnormalities suggest B cell disorders

Complement proteins: abnormalities suggest complement disorder

Antibody responses to vaccines, specifically pneumococcal and haemophilus vaccines

HIV test if clinically relevant

Chest X-ray for scarring from previous chest infections

Sweat test for cystic fibrosis

CT test for bronchiectasis

58
Q

What is severe combined immunodeficiency (SCID)?

A

Immunodeficiency (most severe condition)

Almost no immunity to infection

Caused by genetic disorder causing absent / dysfunctioning T and B cells

59
Q

How does SCID present?

A

First few months of life:

  • Persistent severe diarrhoea
  • Failure to thrive
  • Opportunistic infection e.g. severe / fatal chickenpox
  • Pneumocystic jiroveci pneumonia and cytomegalovirus
  • Unwell after live vaccinations such as the BCG, MMR and nasal flu vaccine
  • Omenn syndrome
60
Q

What genetic mutations can cause SCID?

A
  • Mutation in common gamma chain on the X-chromosome which codes for interleukin receptors on T and B cells (X-linked recessive)
  • JAC3 gene mutation
  • Mutation leading to adenosine deaminase deficiency
61
Q

What is the genetic abnormality in Omenn syndrome?

A

Mutation in the recombination-activating gene (RAG1 or RAG2) which codes for important proteins in T and B cells (autosomal recessive inheritance)

62
Q

What are the features of Omenn syndrome?

A

Red, scaly, dry rash (erythroderma)

Hair loss (alopecia)

Diarrhoea

Failure to thrive

Lymphadenopathy

Hepatosplenomegaly

63
Q

What is the management of SCID?

A

At specialist immunology centre

  • Treat infections
  • Immunoglobulin therapy
  • Sterile environment
  • Avoid live vaccines
  • Haematopoietic stem cell transplantation

Fatal unless successfully treated

64
Q

What do B cells do?

A

Produce immunoglobulins (antibodies)

65
Q

What is a deficiency in immunoglobulins called?

A

Hypogammaglobulinemia (causing susceptibility to recurrent infections especially LRTI)

66
Q

What is the most common immunoglobulin deficiency?

A

Selective immunoglobulin A deficiency (low IgA and normal IgG and IgM)

67
Q

Where is IgA?

A

Secretions of mucous membranes e.g. saliva, respiratory tract secretions, GI tract secretions, tears and sweat - protecting against opportunistic infections

68
Q

How does selective IgA deficiency present?

A

Often aasymptomatic and never diagnosed - tendency to recurrent mucous membrane infections

If testing for coeliacs with IgA anti-TTG and anti-EMA need to test total IgA to rule out deficiency

69
Q

What is common variable immunodeficiency?

A

Genetic mutation in gene coding for components of B cells cauing deficiency in IgG and IgA (with maybe deficiency in IgM)

Causes recurrent resp tract infections (leading to chronic lung disease over time)

Unable to develop immunity to infections or vaccinations

70
Q

What are patients with common variable immunodeficiency also prone to?

A

Rheumatoid arthritis and cancers e.g. non-Hodgkins lymphoma

71
Q

What is the management of common variable immunodeficiency?

A

Immunoglobulin infusion

Treating infections and complications as occur

72
Q

What is X-linked Agammaglobinaemia?

A

X-linked recessive condition causing abnormal B cell development - deficiency in all classes of immunoglobulins (causes issues similar to common variable immunodeficiency)

73
Q

What is X-linked agammaglobulinaemia also known as?

A

Bruton’s agammaglobulinaemia

74
Q

What is DiGeorge syndrome also known as?

A

22q11.2 deletion syndrome

75
Q

What is the genetic abnormality in DiGeorge syndrome?

A

Microdeletion in a portion of chromosome 22 causing a developmental defect in the third pharyngeal pouch and third brachial cleft

76
Q

What is an immune complication of DiGeorge syndrome?

A

Incomplete development of the thymus gland - inability to create functional T cells

77
Q

What are the features of DiGeorge syndrome?

A

C – Congenital heart disease

A – Abnormal faces (characteristic facial appearance)

T – Thymus gland incompletely developed

C – Cleft palate

H – Hypoparathyroidism and resulting Hypocalcaemia

22nd chromosome affected

78
Q

What is purine nucleoside phosphorylase deficiency (PNP)?

A

Autosomal recessive condition (PNPase is an enzyme that helps break down purines_

79
Q

What is a result of PNP deficiency?

A

PNPase is an enzyme which helps break down purines

Without this - metabolite called dGTP builds up

dGTP is toxic to T cells

There are normal levels of B cells and immunoglobulins

80
Q

How do patients with PNP deficiency progress?

A

Immunity to infection gets worse becoming increasingly susceptible to infections particularly viruses and live vaccines

81
Q

What is Wiskott-Aldrich syndrome?

A

X-linked recessive causing a mutation on the WAS gene causing abnormal functioning of T cells

82
Q

What are the other features of Wiskott-Aldrich syndrome?

A

Thrombocytopenia

Immunodeficiency

Neutropenia

Eczema

Recurrent infections

Chronic bloody diarrhoea

83
Q

What is ataxic telangiectasia?

A

Autosomal recessive condition affecting the gene coding for the ATM serine/threonine kinase protein on chromosome 11

Protein is important in functions of DNA coding

84
Q

What are the features of ataxic telangiectasia?

A

Low numbers of T-cells and immunoglobulins

Ataxia: problems with coordination due to cerebellar impairment

Telangiectasia: particularly in the sclera and damaged area of skin

Predisposition to cancers particularly haematological cancers

Slow growth and delayed puberty

Accelerated ageing

Liver failure

85
Q

What is acquired immunodeficiency syndrome?

A

Caused by infection with HIV which reduces the number of CD4 T-cells

86
Q

What are complement proteins?

A

Make up complement system which help destroy pathogenic cells - most important in dealing with encapsulated organisms e.g.:

  • Haemophilus influenza B
  • Streptococcus pneumonia
  • Neisseria meningitidis
87
Q

What do deficiencies in complement proteins result in?

A

Vulnerability to certain infective organisms (in respiratory tract, ears and throat)

88
Q

What are complement deficiencies associated with?

A

Immune complex disorders e.g. systemic lupus erythematous

Incomplete complement cascade leads to immune complexes being deposited in tissues

89
Q

What is the most common complement deficiency?

A

C2 deficiency

90
Q

What is an important part of the management of complement deficiencies?

A

Vaccination against encapsulted organisms

91
Q

What is C1 esterase inhibitor deficiency also known as?

A

Hereditary angioedema

92
Q

What is bradykinin?

A

Part of inflammatory response - causes blood vessel dilatation and increased vascular permeability causing angioedema

93
Q

What is the action of C1 esterase?

A

Inhibits bradykinin

94
Q

What does an absence of C1 esterase cause?

A

Intermittent angioedema in response to minor triggers such as viral infections or stress without any clear triggers at all

95
Q

Where can angioedema effect? What happens?

A

Lips / face / GI tract / larynx

Can last several days

96
Q

What is the prophylaxis against dental / surgical procedures for acute attacks of angiooedema?

A

IV C-1 esterase inhibitor

97
Q

What is the test for C1 esterase inhibitor deficiency (hereditary angioedema)?

A

Check levels of C4 (compliment 4) - levels will be low in the condition

98
Q

How common is mannose-binding lectin deficiency?

A

Relatively common in general population

99
Q

What does mannose-binding lectin deficiency cause?

A

Inhibition of the alternative pathway of the complement system - relatively unimportant in healthy individuals

In patients who are susceptible to infection e.g. CF can cause more severe variant of existing disease

Paediatrics (18 decks)

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