Paediatrics Immunology Flashcards
(99 cards)
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)
2
Q
What is atopy?
A
Term for predisposition to having hypersensitivity reactions to allergens
3
Q
What conditions does atopy encompass?
A
Eczema
Asthma
Hayfever
Allergic rhinitis
Food allergies
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
5
Q
What classification system is used for hypersensitivity reactions?
A
Coombs and Gell classification
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)
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
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)
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
10
Q
How are allergies diagnosed?
A
History
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
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
13
Q
What are skin prick testing and RAST testing assessing?
A
Sensitisation and not allergy (makes these tests notoriously unreliable and misleading)
14
Q
What is the gold standard for diagnosing allergy?
A
Food challenge testing (requires lots of time and resources)
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
16
Q
What testing is used to assess allergic contact dermatitis?
A
Patch testing
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
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
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
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
21
Q
What is immunotherapy?
A
Gradually exposing patient to allergens over months with aim of reducing their reaction
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
23
Q
How do antihistamines and steroids work?
A
Dampening the immune response to allergens
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
25
How to **differentiate** anaphylaxis from non-anaphylactic allergic reaction?
Compromise of the **airway**, **breathing** or **circulation**
26
How does **anaphylaxis present**?
**Urticaria**
**Itching**
Angio-oedema with **swelling around the lips and eyes**
**Abdo** pain
27
Which **additional symptoms indicate anaphylaxis**?
SoB
Wheeze
Swelling of **larynx** causing **stridor**
Tachycardia
Lightheadedness
Collapse
28
What is the **initial management of anaphylaxis**?
**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
29
What **medications** to give during anaphylaxis?
**IM adrenalin** (repeated after 5 minutes if required)
**Antihistamines** e.g. **chlorphenamine** or **cetirizine**
**Steroids** usually IV **hydrocortisone**
30
What is the **management after anaphylaxis**?
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**
31
What are the **adrenalin auto-injector trade names**?
**Epipen**
**Jext**
**Emerade**
32
When are **adrenalin auto-injectors** indicated?
**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
33
How is the **adrenlin auto-injector used**?
**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**
34
What is **allergic rhinitis**?
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
35
What may the **pattern of allergic rhinitis** **be**?
**Seasonal** e.g. **hay fever**
**Perennial** (year round) e.g. **house dust mite allergy**
**Occupational** associated with school / work environment
36
How may allergic rhinitis present?
**Runny, blocked and itchy nose**
**Sneezing**
**Itchy**, **red** and **swollen eyes**
37
How is **allergic rhinitis** diagnosed?
Made on the **history**
**Skin prick testing** can be useful particularly testing for **pollen**, **animals** and **house dust mite allergy**
38
What are the **triggers** for **allergic rhinitis**?
**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
39
What is the **management** of **allergic rhinitis**?
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**
40
What is the **medication** for allergic rhinitis?
**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
What is **good nasal spray technique**?
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
What is **cow's milk protein allergy**?
**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
Who does cow's milk protein allergy affect?
Condition affecting **infants** and **young children** under 3 years
44
How is **cow's milk protein intolerance** different to **lactose intolerance or cow's milk intolerance**?
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
When is **cow's milk protein allergy more common**?
**Formula fed babies**
FH or **atopy**
46
When does **cow's milk protein intolerance** become apparant?
When **weaned from breast milk** or **breast fed babies** when mother is **consuming dairy products**
47
What are the **GI** symptoms of **cow's milk protein intolerance**?
Bloating and wind
Abdo pain
Diarrhoea
Vomiting
48
What are the **allergic symptoms** in response to cow's milk protein?
**Urticarial** rash (hives)
**Angio-oedema** (facial swelling)
**Cough** / wheeze
**Sneezing**
**Watery** eyes
**Eczema**
49
How is **cow's milk protein intolerance diagnosed**?
Full **history and examination**
**Skin prick testing** can help support diagnosis
50
What is the **management of cow's milk protein intolerance**?
**Avoid cow's milk**
If breast feeding then **avoid dairy products**
**Replace formula** with special **hydrolysed formulas** designed for cow's milk allergy
51
What are **hydrolysed formulas**?
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
How does **cow's milk protein intolerance** progress?
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
How does **_cow's milk intolerance_** present?
Same GI symptoms as cow's milk allergy:
* Bloating
* Wind
* Diarrhoea
* Vomiting
**No allergic features** (e.g. rash, angio-oedema, sneezing and coughing)
54
How is **cow's milk intolerence** managed?
**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
How many respiratory infections are normal for a child in a year?
4-8
56
When should **children** with **recurrent infection** be **investigated**?
**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
What are the choice of **investigations** for **recurrent infection in childhood**?
**FBC**: low neutrophils = phagocytic disorder
low lymphcytes = T cell disorder
**Immunoglobulins**: abnormalities suggest **B cell disorder****s**
**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
What is **severe combined immunodeficiency** (SCID)?
**Immunodeficiency** (most severe condition)
Almost **no immunity to infection**
Caused by **genetic disorder** causing absent / dysfunctioning **T and B cells**
59
How does SCID present?
**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
What **genetic mutations** can cause SCID?
* 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
What is the **genetic abnormality** in **Omenn syndrome**?
Mutation in the **recombination-activating gene** (RAG1 or RAG2) which codes for **important proteins** in **T and B cells** (autosomal recessive inheritance)
62
What are the **features** of **Omenn syndrome**?
Red, scaly, dry rash (**erythroderma**)
Hair loss (**alopecia**)
Diarrhoea
Failure to thrive
Lymphadenopathy
Hepatosplenomegaly
63
What is the **management** of **SCID**?
At **specialist immunology centre**
* Treat infections
* **Immunoglobulin therapy**
* **Sterile environment**
* Avoid live vaccines
* **Haematopoietic stem cell transplantation**
Fatal unless successfully treated
64
What do **B cells do**?
**Produce immunoglobulins** (antibodies)
65
What is a **deficiency** in **immunoglobulins** called?
**Hypogammaglobulinemia** (causing **susceptibility to recurrent infections** especially LRTI)
66
What is the most **common immunoglobulin deficiency**?
**Selective immunoglobulin A deficiency** (low IgA and normal IgG and IgM)
67
Where is **IgA**?
Secretions of **mucous membranes** e.g. **saliva**, **respiratory tract secretions**, **GI tract secretions**, tears and sweat - protecting against **opportunistic infections**
68
How does **selective IgA deficiency present**?
Often a**asymptomatic** 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
What is **common variable immunodeficiency**?
**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
What are patients with **common variable immunodeficiency** also prone to?
**Rheumatoid arthritis** and cancers e.g. **non-Hodgkins lymphoma**
71
What is the **management of common variable immunodeficiency**?
**Immunoglobulin infusion**
Treating infections and complications as occur
72
What is **X-linked Agammaglobinaemia**?
**X-linked recessive** condition causing **abnormal B cell development** - deficiency in **all classes of immunoglobulins** (causes issues **similar** to **common variable immunodeficiency**)
73
What is **X-linked agammaglobulinaemia** also known as?
**Bruton's agammaglobulinaemia**
74
What is **DiGeorge syndrome** also known as?
**22q11.2 deletion syndrome**
75
What is the **genetic** abnormality in **DiGeorge syndrome**?
**Microdeletion** in a portion of **chromosome 22** causing a **developmental defect** in the **third pharyngeal pouch** and **third brachial cleft**
76
What is an **immune** complication of **DiGeorge syndrom****e?**
**Incomplete** development of the **thymus gland** - inability to create **functional T cells**
77
What are the **features of DiGeorge syndrome**?
**C** – Congenital heart disease
**A** – Abnormal **faces** (characteristic facial appearance)
**T** – **Thymus** gland incompletely developed
**C** – **C**left palate
**H** – **Hypoparathyroidism** and resulting Hypocalcaemia
**22**nd chromosome affected
78
What is **purine nucleoside phosphorylase deficiency** (PNP)?
**Autosomal recessive condition** (**PNPase** is an enzyme that helps break down purines\_
79
What is a **result of PNP deficiency**?
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
How do patients with PNP deficiency progress?
**Immunity to infection gets worse** becoming **increasingly susceptible to infections** particularly **viruses** and **live vaccines**
81
What is **Wiskott-Aldrich** syndrome?
**X-linked recessive** causing a **mutation on the WAS gene** causing **abnormal functioning of T cells**
82
What are the **other features of Wiskott-Aldrich syndrome**?
**Thrombocytopenia**
**Immunodeficiency**
**Neutropenia**
**Eczema**
**Recurrent infections**
**Chronic bloody diarrhoea**
83
What is **ataxic telangiectasia**?
**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
What are the **features** of **ataxic telangiectasia**?
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
What is **acquired immunodeficiency syndrome**?
Caused by **infection with HIV** which reduces the number of **CD4 T-cells**
86
What are **complement proteins**?
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
What do **deficiencies** in **complement proteins** result in?
Vulnerability to **certain infective organisms** (in respiratory tract, ears and throat)
88
What are **complement deficiencies** associated with?
**Immune complex disorders** e.g. systemic lupus erythematous
Incomplete complement cascade leads to **immune complexes** being deposited in tissues
89
What is the most common complement deficiency?
**C2 deficiency**
90
What is an important part of the management of **complement deficiencies**?
**Vaccination against encapsulted organisms**
91
What is **C1 esterase inhibitor deficiency** also known as?
**Hereditary angioedema**
92
What is **bradykinin**?
Part of **inflammatory response** - causes **blood vessel dilatation** and **increased vascular permeability** causing angioedema
93
What is the **action** of **C1 esterase**?
**Inhibits bradykinin**
94
What does an **absence of C1 esterase** cause?
**Intermittent angioedema** in response to minor triggers such as **viral infections** or **stress** without any clear triggers at all
95
Where can **angioedema** effect? What happens?
**Lips / face** / GI tract / **larynx**
Can **last several days**
96
What is the **prophylaxis** against dental / surgical procedures for **acute attacks of angiooedema**?
IV **C-1 esterase inhibitor**
97
What is the **test** for **C1 esterase inhibitor deficiency** (hereditary angioedema)**?**
**Check levels of** **C4** (compliment 4) - levels will be low in the condition
98
How common is **mannose-binding lectin deficiency**?
Relatively common in general population
99
What does **mannose-binding lectin deficiency** cause?
**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
