Flashcards in urticaria, angiodema and allergy Deck (68)
what is urticaria?
it is a dermatological manifestation that is characterised by the sudden appearance of itchy hives known as wheals, angiodema or both
what does a hive consist of?
three typical features
what are the three typical features of hives?
central swelling of variable size with surrounding reflex erythema
associated itching/pruritus, or a burning sensation
usually resolves within a few hours and always by 24 hours
what does angiodema consist of?
four typical characteristics
what are the four typical characteristics of angiodema?
sudden, pronounced swelling of the lower dermis and subcutis
sometimes pain rather than itch
frequent involvement below the mucous membrane
up to 72 hours for resolution
what are the primary effector cells in angiodema and urticaria?
where are mast cells found?
they are widely distributed in the body, skin and mucosa
what is special about mast cells?
they have high affinity IgE receptors
what does degranulation of mast cells lead to?
the release of inflammatory mediators such as histamine, leukotrienes and prostaglandins
vasodilation and leakage of the plasma in or below the skin
delayed (4-8 hour) secretion of inflammatory cytokines - TNF and IL4/5
further inflammatory responses resulting in longer lasting lesions
what is the basis of the biology of mast cell activation?
there is a trigger - this could be allergy, temperature, exercise or undefined
the cutaneous mast cells release mediators in response to various factors such as drugs, peptides and vasoactive amines
these mediators result in symptom induction such as histamine and interleukins
this results in symptom manifestation
what are the induction methods and what manifestations do these lead to in mast cells?
there is activation leading to pruritus
there is vasodilation leading to erythema
there is extravasation leading to wheal
there is recruitment leading to infiltrate
how are mast cells activated with regards to antigens?
the IgE carrying and antigen will bind to the IgE Fc receptor on the mast cell
this results in signals for: cytokine gene activation, phopsolipase A2 activation and degranulation
degranulation results in granule contents being released
cytokine gene activation results in secreted cytokines
membrane phospholipids from activation
what is the initial mast cell response?
this is histamine, proteases, chemotactic factors (ECF and NCF) - initial response - primary mediators
what is the late phase response?
these are the secreted cytokines
membrane phospholipids result in PAF and arachidonic acid (producing leukotrienes B, C and D4 and prostaglandins D2)
how can acute urticaria be divided?
into IgE mediated and non IgE Mediated causes
what are the non IgE mediated causes of urticaria?
stress - exercise
medications - NSAIDs
what are the IgE causes of urticaria?
insect toxin, drug, aero and food allergies
how can urticaria be classified based on the symptoms?
on the frequency, the duration (acute or chronic) and the cause
what is the definition of chronic spontaneous urticaria or CSU?
it is the spontaneous daily or almost daily occurrence of itchy hives, angiodema or both lasting 6 weeks or more
what is acute urticaria?
symptoms less than 6 weeks
what is spontaneous compared to inducible?
inducible has symptoms induced by a specific trigger
no obvious external specific trigger in spontaneous
what are the divisions of spontaneous for chronic?
known causes such as an inducing autoimmune infection or unknown resulting in CSU
when can CIU be classified as idiopathic and what is it?
it is the skin lesions that are persistent for over 6 weeks with or without angiodema that are daily or episodic - inducible
can be idiopathic when there are exclusion of underlying aetiologies
how would you diagnose CSU?
a routine patient examination with a thorough history and examination that includes:
the shape, size, distribution and associated symptoms of the lesions
the timing, frequency and duration of attacks
FHx and PHMx including allergies
correlation to any triggers
work, hobbies, stress and smoking habits
previous therapies and responses to treatments
which is most common as a combination of symptoms?
hives only or hives and angiodema is most common from 30-70%
angiodema only in 0-20% of patients
what is the epidemiology of CU?
no apparent relationship between urticaria and education, income, occupation, ethnic background or place of residence
all age groups affected bu peak between 20-40 y/o
female:male is 2:1
what is the prevalence of CSU?
affects up to 1% of population at any given time and account for 2/3 of CU cases
what is the disease course of CU?
it is a chronic disease with a duration of around 1-5 years
when is the disease course for CSU likely to be longer?
when the disease is more severe
when there is concurrent angiodema
when there is concurrent inducible urticaria
a positive autologous serum skin test