Allergy Flashcards
What is anaphylaxis (definition)?
any acute onset illness with typical skin features (urticarial rash, errythema / flushing, and/or angioedema) with resp and or cardio involvement. Can also get severe GI involvement
How does anesthetic related anaphylaxis present compared to regular anaphylaxis?
often presents only with spontaneous refractory hypertension during anesthetic (if no other cause found)
- Often don’t get a rash or other features (pt is asleep)
Is elevated tryptase involved in Dx anaphylaxis?
No
- It can be elevated in ana but not always
- Most often elevated in venous or drug anaphylaxis (not often food anaphylaxis)
What time does Mast cell tryptase peak following anaphylaxis? How long does it take to return to normal?
1-1.5hrs post
returns to normal 24 hrs post usually
Why is baseline tryptase recomended following complete resolution of anaphylaxis?
Because anaphylaxis can be an initial presentation of systemic mast cell disorder such as systemic mastocytosis
- If baseline tryptase elevated then this is concerning
Presentation of systemic mastocytosis?
Symptoms of mast cell mediator release
- flushing and pruritis
Skin findings:
- Urticaria pigmentosa
Symptoms arising from organ infiltration
Recurrent anaphylaxis which may be severe
What are teh two types of angioedema? How can these be clinically distinguished?
Histaminergic angioedema (ie as part of ani IgE mediated allergy or anaphylaxis)
- often occures in conjunction with other symptoms of allergy or anaphylaxis
- Shorter duration 2-24 hrs
Bradykinin mediated angioedema
- often occurs in isolation (ie well person with swelling)
- Last longer (24-72hrs)
What are the two types of histaminergic angioedema?
IgE mediated
Non IgE mediated (mast cell degran that is not cuased by IgE crosslinking)
Explain the pathophysiology of hereditary angioedema?
Most commonly caused by a def in C1 inhibitor (aka C1 esterase)
- C1 inhibitor inhibits multiple points in the kallikrein-bradykinin pathway. Hence a deficiency in C1 inhibitor leads to excess bradykinin leading to vascular permeability and angioedema
Note C1 is also invo9lved in complement obviously, but this has nothing to doe with how it causes HAE. Can be used for Dx tho due to low C4 levels
Why do pts with Hereditary angioedema often have low C4?
The have deficiency in C1 inhibitor
C1 inhibitor binds to an inactivates C1r and C1s which stops the cleavage of C4 and activation of classical complement pathway
therefore if dont have this inhibitor, C4 is always being cleaved resulting in low levels of C4
What distribution of angioedema would be more concerning for HAE rather than ACEI mediated angioedema?
Genitral or GIT angioedema = HAE
What are the 4 types of HAE?
Type 1 (most common)
- Quantatative C1 inh def
Type 2
- Qualatative C1 inh def
Type 3
- Abnormalities in other proitiens involved in pathway (often get normal C4 level in T3)
type 4
- aquired def due to antibodies against C1 inh (usually old pts with haem malig or autoimmunity)
what is the utility in testing for C1q in HAE?
It is low in acquired HAE (ie Type 4), normal in all others
Management of HAE? (acute attacks, short term prophylaxis, long term prophylaxis)
Acute attack:
- Icatibant (bradykinin receptor antagonist)
- Berinert IV (recombinant C1 inh)
Short term prophylaxis:
- Berinert IV stat prior to procedure (ie dental procedures or intubation
Long term prophylaxis:
- Berinert IV or SC
- Lanadelumab ( kallikreinin inhibitor mab)
What time frame can ACEI related angioedema develop?
Can occurs many years after starting drug
