Urticaria Flashcards
Dermatology
Define urticaria (hives)?
Inflammatory skin condition characterised by wheals
What condition usually occurs with urticaria and why?
Angioedema
Both have same immune process
Define angioedema?
Swelling in subcutaneous tissue (under skin) that lasts up to 3 days
Is urticaria equally common in all ages?
No, less common in children than adults
Does everyone develop urticaria during their lifetime?
No, up to 20% individuals will develop urticaria once in their lifetime
What cell type causes the pathophysiology of urticaria?
Mast cells
How is mast cell degranulation triggered, in the pathophysiology of urticaria?
Autoantibodies/allergens bind to high affinity IgE receptors on mast cells or basophils, or bind to IgE that is already bound to receptor
What 6 substances are released from mast cell granules, in the pathophysiology of urticaria?
Histamines
Proteases
Platelet activating factor
Leukotriene C4
Prostaglandin D2
How does mast cell degranulation cause urticaria symptoms?
Causes plasma leakage from capillaries, which causes swelling and itching
Does urticaria always occur due to the same immune mechanism?
No, can result from different immune mechanisms that have similar presentations
Give 2 examples of immune mechanisms that can cause urticaria?
Type 1 immediate hypersensitivity due to an allergen, which is tested for with skin-prick testing
Type V stimulatory hypersensitivity due to an autoantibody
What is the main difference between acute and chronic urticaria?
Acute urticaria lasts less than 6 weeks
Chronic urticaria lasts more than 6 weeks
Give 7 known causes of acute urticaria?
Food
Medications (NSAIDs, aspirin, codeine)
Insect stings and bites
Viral or bacterial infection
Contact allergy to latex
Transfusion
Vaccination or idiopathic
Does acute urticaria always have a known cause?
No, can be idiopathic
What is the most dangerous complication of severe acute urticaria?
Can progress to anaphylactic shock
What is the difference between chronic inducible urticaria and chronic spontaneous urticaria?
Inducible: Has known trigger
Spontaneous: Has unknown trigger (idiopathic)
Give 5 conditions that can cause chronic inducible urticaria?
Autoimmune conditions eg. urticarial vasculitis
Autoantibodies
Neoplastic
Urticaria pigmentosa
Idiopathic
What type of urticaria is caused by lightly scratching skin?
Symptomatic dermographism: lightly scratching patient’s skin causes raised, inflamed lines or welts that tend to go away in less than 30 minutes
What type of urticaria is caused by sunlight?
Solar urticaria
What type of urticaria is caused by cold air, water or ice?
Cold contact urticaria
What type of urticaria is caused by heat?
Heat contact urticaria
What type of urticaria is caused by sweating?
Cholinergic urticaria