Urticaria & Angiodema Flashcards
What is the definition of urticaria?
a dermatological manifestation characterised by the sudden appearance of itchy hives (wheals), angioedema or both
What is meant by a ‘hive’?
superficial swelling with a pale centre surrounded by a red flare
What are the 3 typical features of a hive?
- central swelling surrounded by a reflex erythema
- associated itching (pruritus) and sometimes a burning sensation
- usually resolves in a few hours and always resolves by 24 hours
What is meant by erythema and what is it caused by?
redness of the skin caused by hyperemia (increased blood flow) in superficial capillaries
What are the 4 main characteristics of angioedema?
- sudden pronounced swelling of the lower dermis and subcutis
- sometimes pain rather than itching
- frequent involvement below mucous membranes
- up to 72 hours for resolution
What are the primary effector cells in urticaria and angioedema?
Where are they found?
Mast cells
Widely distributed in skin, mucosa and other areas of the body
What type of receptors are present on the surface of mast cells?
high affinity IgE receptors
What inflammatory mediators are released when a mast cell degranulates?
There is rapid release of histamine, leukotrienes, prostaglandins
There is delayed release (4-8 hr) of inflammatory cytokines
e.g. TNF, IL-4/5
What is the physiological outcome of mast cell degranulation?
Vasodilation and leakage of plasma in/below the skin
What happens for the first time when someone is exposed to an allergen?
The body makes large amounts of IgE antibody against the allergen
The IgE molecules attach themselves to mast cells
What happens when someone is exposed to an allergen for the second time?
IgE primed mast cells release granules and chemical mediators
These cause the characteristic symptoms of allergy
How can mast cell activation lead to the symptoms of urticaria?
The trigger can be heat, cold, exercise, undefined
Mast cells release mediators in response to drugs, peptides, etc.
Mediators cause symptom induction
What are the 2 types of acute urticaria?
- IgE-mediated urticaria
2. Non-IgE-mediated urticaria
What are the 4 typical triggers of IgE-mediated urticaria?
- drug allergy
- food allergy
- insect toxin allergy
- aeroallergies
What are the 4 typical triggers of non-IgE-mediated urticaria?
- infection
- medications (e.g. NSAIDs)
- Stress (exercise)
- idiopathic
What are the 3 ways of classifying urticaria?
- duration
- frequency
- cause
What is the difference between chronic and acute urticaria?
Chronic - daily symptoms for 6 weeks or more
Acute - symptoms for less than 6 weeks
What are the 2 types of chronic urticaria?
- spontaneous
2. inducible
What is spontaneous urticaria?
There is no obvious external specific trigger
What is inducible urticaria?
Symptoms are induced by a specific trigger
e.g. temperature, pressure
What is the definition of chronic spontaneous urticaria (CSU)?
Spontaneous daily occurrence of itchy hives, angioedema or both, lasting for 6 weeks or more
When taking a history of someone thought to have CSU, what are the 6 main areas that should be explored?
- timing/frequency/duration of attacks
- shape, size and distribution of lesions
- family and medical history - including allergies
- correlation to any triggers
- work/hobbies/smoking habits
- previous therapy and response to treatment
Typically for how long will someone with CSU suffer for?
It is a chronic disease which typically lasts between 1 and 5 years
What 4 factors suggest that CSU duration will be longer than 1-5 years?
- more severe disease
- concurrent angioedema
- concurrent inducible urticaria
- positive autologous serm skin test
