IC9 Immune-mediated toxicities Flashcards
types of allergy
immune (allergy)
non-immune (pseudoallergy)
immune (allergy): types of hypersensitivity reactions
- Immediate → IgE mediated; atopy
Type I, II, III hypersensitivity reactions → occurs within 24 hours of exposure - Delayed → IgM, IgG, T cell mediated
Type IV hypersensitivity reaction
immune (allergy): prevalence
~10-15% of all ADR
cause of non-immune (pseudoallergy)
Drugs causing release of mediators: histamine, prostaglandins, bradykinins → often mast cell & basophil derived
By pharmacologic/ physical effect
non-immune (pseudoallergy): prevalence
~77% of hypersensitivity reactions
Effectors of drug hypersensitivity reactions
Involving major components of innate & adaptive immune systems
Involving release of pharmacologically active chemical mediators
Effectors of drug hypersensitivity reactions: innate & adaptive components
Cellular elements: macrophages T & B lymphocytes, platelets, mast cells
Immunoglobulins: especially IgE (associated to type I AR, immediate reaction)
Complements: activation of mast cells & inflammatory mediators
Cytokines
Effectors of drug hypersensitivity reactions: pharmacologically active chemical mediators
Histamine, platelet-activating factor (PAF), prostaglandins (PG), thromboxanes, leukotrienes
clinical manifestations (main ones)
anaphylaxis
severe cutaneous adverse reactions
others:
serum sickness/ drug fever
drug induced autoimmunity
vasculitis
haematologic
respiratory
clinical manifestations: anaphylaxis definition
Acute & life-threatening, involves multiple organ systems
First few hours ⇒ highest risk of fatal anaphylaxis
clinical manifestations: anaphylaxis organs involved
skin, CNS, GIT
respiratory - bronchoconstriction: difficulty breathing, SOB, chest tightness
CVS: low BP, high HR, chest pain
clinical manifestations: anaphylaxis first line treatment + how does it work
epinephrine
Acts on ⍺ & β receptors
Counteracts bronchoconstriction & vasodilation
clinical manifestations: anaphylaxis hospital treatment
IV fluids → restore volume/ BP
Intubation PRN → to save airway
Norepinephrine (noradrenaline) → if shock
Others:
possible agents:
Steroids → suppresses later reactions
Glucagon (if patient currently on BB) → helps with chronotropic & inotropic effects, for regular heart beat
H1 [diphenhydramine] + H2 [ranitidine] → blocks all histamine receptors, to slow down reactions
clinical manifestations: SCAR types
DRESS, TEN, SJS
clinical manifestations: SCAR (DRESS presentation)
Triad of rash, eosinophilia & internal organ involvement
clinical manifestations: SCAR (DRESS mortality)
10%
clinical manifestations: SCAR (SJS & TEN presentation)
Progressive bullous or “blistering” disorders → dermatologic emergencies
Progress to include mucous membrane erosion & epidermal detachment
clinical manifestations: SCAR (SJS & TEN extent of symptoms)
SJS: less than 10% detachment of body surface area
TEN: greater than 30%
clinical manifestations: SCAR (SJS & TEN mortality)
SJS: 1% to 5%
TEN: 10% to 70%
clinical manifestations: SCAR treatment guide
- No defined cure; important to stop taking causative drug
- Supportive care (similar to burn patients): Wound care, nutritional support, fluids, temperature regulation, pain management & prevention of infection
- Possible steroid use (not first line)
- IV immunoglobulin, cyclosporin
SLE
how it is a multisystem disease
Associated with auto-Ab production
immune-mediated complex can be anywhere in the body
SLE
how is it a multifactorial disease
- Strong genetic disposition
Present in first degree relatives ⇒ 20x more likely - environmental factors
smoking, infection, drugs, pollution, UV light, Epstein-Barr virus (herpes)