20. Allergic disorders. Flashcards
what is IgE mediated type 1 allergy?
the allergen taken by antigen representing cell - presenting to Th cell - activating it into a TH2 cell - stimulates B cell to produce IgE antibodies which then goes to mast cells and basophils = sensitisation
next time the allergen directly stimulates the mast cells
Atopy is the genetic predisposition to make IgE antibodies in response to allergen exposure.
Mast cells and basophils have a high affinity IgE cell membrane receptors for IgE
what are the phases in IgE mediated hypersensitivity ?
step 1 - sensitisation
step 2 - early phase within minutes (immediate reaction)
through degranulation os wast cells
step 3 - late phase response
hours
through endothelia cel activation and leukocyte infiltration
what are the symptoms for allergic asthma
asthma - wheezing , dyspnea , tachypnea
route of entry - inhalation
what is the clinical manifestation of atopic dermatitis(eczema)
urticaria (hives , angioedema) ?
atopic dermatitis is chronic
Intense pruritis and dry skin:
in infants most often on cheeks and scalp , wrist , extensor as pects
the nappy area is usually spared
Dennie-Morgan fold: increased folds below the eye
2-12 years - dry itch skin on flexor surfaces of the body - inside of elbow , creases of wrist, back of knee , face , hands, feet
it can then become red , then blister and peel and lichenified
is worst at night (due to no distractions)
teenagers - flexural surfaces , face especially periorbital region , hands and feet
====== prurutic vesicular lesions or pruritic bullous lesions Well-circumscribed, raised, erythematous plaques with a round / oval, / serpiginous shape
Up to several centimeters in diameter (wheals)
angioedema of the laryngopharynx can obstruct airway - difficulty breathing / stridor / hoarseness = life threatening
due to maybe ingestion of foods.
nuts, chocolate, fish, tomatoes, eggs, fresh berries, and milk.
what causes atopic dermatitis
polygenetic inheritance
Mutation in the filaggrin gene → abnormalities in epidermal skin barrier formation → entry and interaction of antigens with immunogenic cells
Triggers Dust mites Heat Extremely dry or humid climate Emotional stress Pollen Pet fur Fabrics Soap
usually people with atopic dermatitis have food allergy.
how do we clinically diagnose atopic eczema / urticaria ?
four criteria is sufficient
pruritus
stigmata of atopy - Typical morphology and age-specificdistribution patterns
early onset
chronic or relapsing course
Exclusion of other cond itions
————
igE mediated
atopy- family history
xerosis
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urticaria - fam history
in vivo skin test
Skin prick test
Tiny amounts of various allergens are applied to the skin; a lancet is then used to prick the surface of the skin so that allergen extracts may enter.
Scratch test
Intradermal injection test
in vitro
Tryptase in serum (a relatively specific marker of mast cell activation):.
Allergen-specific IgE
in patients in whom the risk of anaphylaxis is high (ELISA)
Total IgE.
punch biopsy of the lesion should be performed and sent to the pathology laboratory to look for leukocytoclastic vasculitis
how do we treat atopic eczema
Sedat In first generation antihistamines if itchy
primary preventioon f breast feeding
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very mild = emollients ,regular bathing
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l
mild to moderate
topical steroids
hydrocortisone 1 percent - low potency twice daily
topical calcineurin inhibitors
moderate - severe - non pharmacological - wet wrap therapy
icrease topical potency
medium potency -
triamcinolone 0.1 percent - twice daily
high potency - fluocinomide - 0.05 percent
consider corticosteroid systemic therapy
phototherapy
immunomodulators - cyclosporine
Azathioprin
Mycophenolate ‘
how do we treat urticaria ?
cetirizine - NOT ACUTE
oral (doses given here)
IV - indicated in acute cases aged over 6 months
<5 years - 2.5mg IV daily
<12 years - 5-10mg IV daily
>12 years - 10mg IV daily
IF ACUTE!!! -
diphenhydramine (Benadryl)
IM/IV
1 mg/kg/dose
2-6 years: 6.25 mg q4-6hr
6-12 years: 12.5-25 mg PO q4-6hr
>12 years: 25-50 mg PO q4-6hr
use the liquid or rapid-dissolving tablet
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oral glucocorticoids in acute cases - if urticaria does nt fade in 2hrs with Benadryl
prednisone at a dose of 1 mg/kg/ day
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for chronic idiopathic urticaria- Omalizumab (FDA approved) children over 12 years
150-300mg subcutaneously every 1 month
what is the clinical manifestation of allergic gastroenetropathy ?
committing diarrhoea
what are the triggering factors of anaphylaxis ?
food - 30 min onset of symptoms
insect - 15 min
medication - 5 min
what is the clinical manifestation of systemic hypersensitivity
anaphylaxis -
shock , hypotension ,
flushing
wheezing. dysphasia - angioedema of throat / bronchoconstriction
hoarseness ,
swelling of eyelids , angioedema (urticaria)
chest tightness
nausea , vomitting , diarrhea , abdominal cramping
uterine cramping and urinary urgency
death within 15 minutes
due to insect or venom or drugs such as penicillin
the causes of anaphylaxis are divided into two major groups ?
age mediated
initial sensitising exposure
non ige mediated - do not require ige immune reaction - direct stimulation of mast cells and basophils - no sensitisation is required
what is the management of anaphylaxis ?
call for help , lie the patient flat and raise their legs ( patients should be placed supine or in the Trendelenb urg position, which optimizes venous return )
A-E approach
positive pressure ventilation / Bambu bag( bag valve mask)
or biPAP
secure the airways -
intubate
Severe bronchospasm: Administer a bronchodilator.
SABA: e.g., albuterol nebulizer OR albuterol MDI
Consider a muscarinic antagonist additionally: e.g., ipratropium (off-label use
Fluid resuscitation
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intramuscular epinephrine shot
1:1000 concentration ( 1:1,000 solution into a vein leads to cardiac arrest)
0.01mg/kg !!
<6 years = 150mcg
6-12= 300mcg
>12 = 500mcg
adrenaline IV can only be given by trained specialists
repeat after 5 mins if no better
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aggressive IV colloid (normal saline) resuscitation - large bore IV access
20ml/kg
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chlorphenamine - IM or slow IV <6months - 250mcg/kg 6mo-6yr = 2.5mg <12 yr = 5mg >12 = 10mg
or
5 hydrocortisone - IM or slow IV 25mg 50mg 100mg 200mg
or
antihistamines
h1 - diphenhydramine
1 mg/kg IV/IM/PO every 6 hours
h2 - ranitidine - 1 mg/kg IV once as needed
what is the atopic triad ?
atopic dermatitis
asthma
allergic rhinitis
which runs in families
symptoms for
allergic rhinitis ,
sinusitis - usually with allergic rhinitis
conjunctivitis ,
hay fever symptoms
rhinorrhea , nasal congestion postnasal drip
Itchy nose
allergic rhinitis commonly mistreated in children as recurrent sore throat and URTI
sneezing,
itchy throat
chronic cough is common in allergic rhinitis or sinusitis due to POSTNASAL DRIP
Cobblestone appearance of the posterior pharyngeal wall
hypertrophic turbinates
Nasal polyps seen in 25–30% with chronic allergic rhinitis.
Allergic shiners: hyperpigmentation and edema of the lower eyelid as a result of venous congestion
typical of pollen and contact through mucus membrane
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redness
itching eyes
what is the classification of allergic rhinitis ?
ARIA GUIDELINES
episodic
seasonal
perennial - Exposure to allergens that are normally a part of the patient’s environment (e.g., allergic rhinitis caused by house dust)
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frequency
intermittent - < 4 days/week OR < 4 weeks/year
persistent - > 4 days/week OR > 4 weeks/year
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severity
mild - not interfering with quality of life
normal sleep /activities etc
moderate
how can we differentiate allergic rhinitis from paediatric rhinitis
paediatric rhinitis - cough , sneezing , nasal pruritus , nasal congestion , sore throat
allergic - conjunctivitis , pharyngitis , sinusitis , asthma, eczema , otitis media
allergic rhinitis is common with what other atopic diseases ?
allergic sinusitis
ASTHMA
otitis media - allergy is a risk factor for otitis media due to the dysfunction in eustachian tube
how does allergic rhinitis cause otitis media
inflammation - mucosal swelling - obstruction of eustachian tube - negative pressure and impaired ventilation in the middle ear , aspiration of fluid in middle ear during opening - acute otitis media - leading to chronic otitis media
how do we diagnose for allergic rhinitis
take detailed history and family history - he time, duration, and frequency of symptoms, suspected exposures, and exacerbating/alleviating factors, and seasonality
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in vivo
if it is IgE mediated - SKIN PRICK TEST
scratch test
Intradermal allergy testing
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in vitro
try-tase in serum
RAST -radioallergosorbent test blood to see if they have any allergies
total igE
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Anterior rhinoscopy typically reveals swelling of the nasal mucosa and thin, clear secretions. The inferior turbinates may take on a bluish hue, and cobblestoning of the nasal mucosa may be present.
Pneumatic otoscopy can be used to assess for eustachian tube dysfunction, which can be a common finding in patients with allergic rhinitis. Palpation of sinuses may elicit tenderness in patients with chronic symptoms.
positive response to empiric treatment with a nasal glucocorticoid can support the diagnosis
how do we treat allergic rhinitis ?
Avoid exposure to the putative allergen (e.g., dust, animal dander, mold spores, plant pollen, or latex)
mites - vacuum with HEPA FILTER
Pharmacotherapy: Therapy is usually begun empirically without diagnostic confirmation.
first line : Intranasal corticosteroid therapy
for age over 6 = beclomethasone dipropionate 1 spray (42mcg) in each nostril twice daily
or
flunisolide 1 spray (25mcg) in each nostril three times daily
for children 2 years and more - mometasone 1 spray (50mcg) in each nostril once daily
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second line - in combination with oral antihistamines
2nd generation antihistamines - but has sedative effect
citirizine 6months - 2.5mg OD oral solution >12months - 2.5mg OD oral solution 2-5 years - >2.5-5mg OD >6 years - 5-10mg OD
levocetrizine 6 mo = 1.25mg OD >12mo = 1.25mg OD 2-5 yrs = 1.25mg OD >6 yrs = 2.5mg OD >12 years = 5mg OD
desloratadine - no sedation 1mg OD 1.25mg OD 1.25mg Od 2.5 mg OD 5mg OD
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intranasal sodium cromolyn spray
<2years - no safety efficacy established
>2 years - 1 spray (5.2mg) / 3-6 doses a day to short half life but there is poor compliance
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INTRANSAL anticholinergics - for RHINORRHEA
ipratropium intranasal spray (atrovent)
<5 years no data
5-12 = 2 spray (0.06 percent ) in each nostril every 8 hours a day
>12 = 6 hours
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nasal decongestion
phenylephrine
2-6 years = 1-3 drops intransaly every 4 hour of 0.125 percent solution not to exceed 3 days
6-12years - 2-3 drops of 0.25 % solution every 4 hr , not to exceed 3 days
> 12 years
1-2 sprays / 1-2 intranasal drops every 4 hours of 0.25 parent solution not to exceed 3 days
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antileukotrines - not recommended for mono therapy for allergic rhinitis without asthma
what is the definition of food allergy ?
AN IMMUNOLOGICAL RESPONSE TO FOOR PROTEIN (food intolerance is usually to carbohydrates )
SMALL amount cause SEVERE AND LIFE THREATENING REACTIONS
what are food allergy symptoms ?
in comparison to food intolerance ?
allergic rhinitis atopic dermatitis ACUTE urticaria - USUALLY 2HRS of ingestion conjuctivitis asthma/ wheezing diarrhea stomach cramps comitning anaphylaxis
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migraine headaches joint pain , non specific ache stomach ache , constipation diarrhea
how do we diagnose food allergy
for both
take a detailed history and family history - he time, duration, and frequency of symptoms, suspected exposures, and exacerbating/alleviating factors, and seasonality
if it is IgE mediated - SKIN PRICK TEST
Intradermal allergy testing
OR
RAST
food allergy
if non ige mediated - challengee or endoscopy
