Paediatric immunology Flashcards
Explain the difference between cows milk protein allergy and cows mil intolerance
- Allergy : hypersensitivity to cow’s milk. can be IgE mediated where there is a rapid reaction or non-IgE mediated where rthe reaction occurs over several days
- Intolerance : nit an allergic process and does not involve the immune system
what GI symptoms are seen in both cow’s milk allergy and intolerance
Bloating and wind
Abdominal pain
Diarrhoea
Vomiting
What additional symptoms are seen in cow’s milk protein allergy
Urticarial rash (hives)
Angio-oedema (facial swelling)
Cough or wheeze
Sneezing
Watery eyes
Eczema
Rarelu : anaphylaxis
If not clinical, what can be done to support the diagnosis of CMPA
Skin prick testing
How is CMPA managed ?
- Breast feeding mothers should avoid dairy products
- Replace formula with special hydrolysed formulas
- Severe cases : elemental formulas of basic amino acids
Explain a type 1 hypersensitivity reaction
- IgE mediated
- Immediate reaction
- E.g. Food allergies
Explain a type 2 hypersensitivity reaction
- IgG and IgM mediated
- E.g. Haemolytic disease of the newborn and transfusion reactions
Explain a type 3 hypersensitivity reaction
- Immune complexes cause damage to local tissues
- E.g. SLE, RA and HSP
Expain a type 4 hypersensitivity reaction
- Caused by T lymphocytes
- E.g. Organ transplant rejection, contact dermatitis
Give two commonly used tests for diagnosing allergies
- Skin prick
- Radioallergosorbent (RAST) : determines amount of IgE that reacts to suspected allergies
What allergy testing is useful for contact dermatitis ?
Skin patch testing
what causes anaphylaxis ?
- Severe type 1 hypersensitibty reaction
- IgE mediated = mast cells degranulation
What is the immediate management of anaphylaxis ?
- > IM adrenalin, repeated after 5 minutes if required
- > Antihistamines, such as oral chlorphenamine or cetirizine
- > Steroids, usually IV hydrocortisone
How is anaphylaxis confirmed ?
- Measuring serum mast cell tryptase within 6 hours of the event
Explain the adrenaline dose for anaphylaxis based on age
- <6mnths : 100-150micrograms
- 6mnths - 6 yrs : 150
- 6-12 yrs : 300
- Adult & child >12 yrs : 500
what is the best site of IM adrenaline injection
Anterolateral aspect of the middle third of the thigh.
what causes allergic rhinitis ?
- IgE mediated type 1 hypersensitivity reaction to environmental allergens in the nasal mucosa
How does allergic rhinitis present ?
- Runny, blocked and itchy nose
- Sneezing
- Itchy, red and swollen eyes
How can allergic rhinitis be managed ?
- Avoid trigger
- Oral antihistamines
- Nasal corticosteroid spray
Explain the different types of antihistamine
- Non sedating : cetirizine, loratadine, fexofenadine
- Sedating : chlorphenamine (piriton), promethazine
What is SCID
- Severe condition causing immunodeficiency in children
- Results in absent or dysfunctioning T and B cells
what causes most cases on SCID
- Mutations in the common gamma chain on the X chromosome that codes for interleukin receptors on T and cells
- X linked recessive
How does SCID present ?
First few mnths of life with :
- Persistent severe diarrhoea
- Failure to thrive
- Opportunistic infections that are more frequent or severe than in healthy children
- Unwell after live vaccinations such as the BCG, MMR and nasal flu vaccine
what is a rare cause of SCID
- Omenn syndrome
What are the classic features of Ommen syndrome ?
- A red, scaly, dry rash (erythroderma)
-Alopecia - Diarrhoea
- Failure to thrive
- Lymphadenopathy
- Hepatosplenomegaly
What is an example of a cause of mild immunodeficiency
- Selective immunoglobulin A deficiency
- Pts have a tendency towards recurrent mucous membrane infections (e.g. LRTI, autoimmune conditions).
Name 3 B cell or immunoglobulin disorders
- Selective immunoglobulin A deficiency
- Common variable immunodeficiency
- X-linked Agammaglobulinaemia
Name 5 T cell disorders
- DiGeorge syndrome
- Purine Nucleoside phosphorylase deficiency
- Wiskott-Aldrich syndrome
- Ataxic Telangiectasia
What causes DiGeorge syndrome
- Microdeletion in a portion of chromosome 22
- Incomplete development of thymus gland -> inability to create functional T cells
What are the features of DiGeorge syndrome
CATCH-22
- C – Congenital heart disease
- A – Abnormal facies (characteristic facial appearance)
- T – Thymus gland incompletely developed
- C – Cleft palate
- H – Hypoparathyroidism and resulting Hypocalcaemia
- 22nd chromosome affected
what is purine nucleoside phosphorylase deficiency ?
- Autosomal recessive condition causing a deficiency in PNPase
- Without it, build up of dGTP = toxic to T lymphocytes
What is Wiskott-Aldrich syndrome ?
- X linked recessive condition with a mutation on WAS gene = abnormal functioning T cells
What are the features of WAS
- Thrombocytopenia
- Immunodeficiency
- Neutropenia
- Eczema
- Recurrent infections
- Chronic bloody diarrhoea
What is Ataxic Telangiectasia ?
- Autosomal recessive condition affecting the gene coding for the ATM serine / threonine kinase on chromosome 11
What are the features of ataxic telangiectasia ?
- Low numbers of T-cells and immunoglobulins, causing immunodeficiency and recurrent infections.
- Ataxia
- Telangiectasia, particularly in the sclera and damaged areas of skin
- Predisposition to cancers, particularly haematological cancers
- Slow growth and delayed puberty
- Accelerated ageing
- Liver failure
Name 2 complement disorders
- Hereditary angioedema
- Mannose-Binding Lectin Deficiency
A patient presents with episodes of unexplained lip swelling (angioedema). What test should you perfrom and what is the likely underlying diagnosis ?
- C4 levels
- If C1 esterase inhibitor deficiency (hereditary angioedema) is the underlying cause, the C4 levels will be low.
