Allergy Cram Flashcards
When NOT to use allergen specific IgE tests?
Tolerating food without IgE reaction
Food “intolerance”
Chronic idiopathic urticaria
Contraindication to oral food challenge?
Skin prick test >3mm positive
ssIgE >0.35
Recent hx of reaction
What medications to withhold pre-skin prick testing?
Oral antihistamines - 5 days
Some antidepressants (amitriptyline, mirtazepine) - 7 days
Antipsychotics (Quetiapine, olanzepine) - 2 weeks
Anti-emetics (chlorpromazine) - 2 weeks
Factors influencing SPT result?
Recent anaphylaxis
Dermatographism
Diagnosis of anaphylaxis?
Skin features - rash/erythema/flushing/angioedema
AND
resp/cardio/GI sx OR hypotension
For insect bite/stings GI sx alone is enough for anaphylaxis dx
Risk factors for fatal anaphylaxis?
Adolescence
Nut/shellfish allergy
Poorly controlled asthma
Delays to treatment
Do not let children with anaphylaxis _____
Stand or walk suddenly - risk of death
Who to prescribe EpiPen to?
Any person with food anaphylaxis
Type 1 hypersensitivity?
Immediate
IgE mediated
Anaphylaxis, urticaria, atopy
Type 2 hypersensitivity?
Sub-acute
Antibody dependant cytotoxic - IgM, IgG, IgA
Haemolytic anaemia, Goodpasture, Myasthenia
Type 3 hypersensitivity?
Sub-acute
Immune complex
Serum-sickness like reaction, SLE, GN, HSP
Type 4 hypersensitivity?
Delayed
Cell mediated - Lymphocytes
Contact dermatitis, TENS/SJS, transplant rejection, T1DM
Risk factors for allergic rhinitis?
Fix atopy Elevated IgE by age 6 Maternal heavy smoking Indoor allergens LUSCS
Risk of asthma if allergic rhinitis in childhood?
3 fold increase in asthma at an older age
Pathophysiology of eczema?
- Defective epidermal barrier function - allows allergens to penetrate barrier. Keratinocytes induce cutaneous immune reaction.
- Immune dysregulation cutaneous lymphocytes increase Th2 cytokine response and IL5
Mutation in patients with severe atopic dermatitis?
Filaggrin gene defect in 50%
Severe autosomal recessive eczema with SPINK5 mutation?
Netherton Syndrome
Pimecrolimus mechanism and SEs?
Calcinuerin inhibitor
Irritation, burning, erythema, infections/folliculitis and rarely desquamation
Can result in peri-oral dermatitis
Difference between peri-oral dermatitis and eczema?
Peri-oral dermatitis has zone of sparing around lips
Rebound effect of steroids/pimecrolimus on face
Treat peri-oral dermatitis with erythromycin/tetracycline
Super infections in eczema?
Staph aureus - golden crust. Mx bleach baths and PO abx
HSV - vesicles. PO antivirals
Tinea - topical antifungals
Malessezia furfural yeast
Treatment of large local reaction to insect bite/sting? Risk of future anaphylaxis follow large local reaction to insect bites/sting?
PO pred, antihistamine for pruritus and NSAID for pain.
7%
Conjunctivitis of upper tarsal surface. Exacerbations in spring/summer and itching worse with light/sweat. Long eyelashes.
Vernal conjunctivitis
Conjunctivitis of lower tarsal surface with associated atopic dermatitis
Atopic conjunctivitis
Conjunctivitis assoc w contact lens wear
Giant papillary conjunctivitis
Urticaria VS angioedema?
Urticaria = causes swelling of dermis Angioedema = swelling of dermis, submit tissues, mucus membranes
Angioedema without urticaria
Drug induced
Hereditary
C1 esterase inhibitor deficiency
Recurrent episodes of hand/feet/genital swelling lasting a few days. Sometimes assoc w severe abdominal pain, N+V/diarrhoea. Now presents with feeling of lump in throat
Hereditary angioedema
Cutaneous, GI, laryngeal/pharyngeal
50% at some point have laryngeal/pharyngeal involvement
Treatment of angioedema attacks?
NOT responsive to adrenaline, antihistamines or glucocorticoids
Recombinant/plasma derived C1 concentrate
Rash, fever, polyarthralgia 7 days after receiving snake anti-venom/MAB therapy. Bloods show low c3/c4 and low total haemolytic complement
Serum Sickness
Rash, fever, poly arthritis 2 weeks after cefaclor course.
Serum sickness like reaction
4 week old baby with blood speckled stool. No FTT, vomiting or frank blood. Mo breastfeeds. Dx and Mx?
Allergic proctocolitis
Remove trigger from diet/maternal diet if BF
Usually resolves by 12mths of age - can reintroduce
Baby with chronic, non-bloody diarrhoea after introducing cow’s milk/egg/wheat. Abdo distention. Fatty stool. Bloods show anaemia and low albumin. Dx and Mx?
Food protein enteropathy
Allergen avoidance
Usually outgrown by 2-3yrs old and can re-introduce then
Intestinal biopsy findings of food protein enteropathy?
Villous atrophy due to T cell activation
Baby with vomiting, diarrhoea and hypotension after introduction of rice. Previously hospitalised for ‘sepsis’.
FPIES
Severe FPIES blood gas findings
Metabolic acidosis and methaglobinaemia
Risk of developing atopy if FPIES in infancy?
30%
When is soy formula not recommended?
<6mths old
Higher rate of concurrent soy allergy in younger infants
Nutritionally suboptimal
Flu like sx with rash beginning on torso and spreading out. Mucosa is affected. Biopsy shows full thickness epidermal necrosis. Dx?
Stevens-Johnson Syndrome / Toxic Epidermal Necrolysis
Consider prednisolone/cyclosporin
Nikolsky sign?
Blistering where skin is rubbed/pressure point seen in SJS/TENS
Likelihood a child will have an topic disease when a first degree relative is affected?
75%
