Urticaria (DERM)

Question 1

Define urticaria.

Answer 1

Erythematous, blanching, oedematous, non-painful, pruritic lesions that develop rapidly, usually over minutes

Question 2

How long does urticaria typically last?

Answer 2

<24 hours and leaves no residual skin markings upon resolution

Question 3

What are some episodes of urticaria associated with?

Answer 3

Approximately 40% of episodes have associated angio-oedema (sudden, pronounced swelling of the subdermis/mucous membranes, may be painful rather than itchy + lasts up to 72h)

Question 4

What is the difference between acute and chronic urticaria?

Answer 4

• acute - occur over a period of <6 weeks, usually caused by a specific stimulus, self-limiting
• chronic - occur over a period >6 weeks and are rarely attributable to a specific stimulus

Question 5

What is the aetiology of urticaria?

Answer 5

• caused by activation of mast cells in the skin –> release of histamines
• cytokine release –> capillary leakage –> skin swelling and vasodilation –> erythematous appearance

Question 6

What is acute urticaria triggered by? (3)

Answer 6

• mainly allergy related (food and drugs) = IgE mediated; direct mast cell degranulation
• insect bites, contact with allergens
• viral infections (non-IgE mediated mechanisms)

Question 7

What is chronic urticaria triggered by? (7 + 1)

Answer 7

• heat
• cold
• pressure
• sunlight
• vibration
• ACh release
• water

Autoimmune/antibody associated in nature –> presence of IgG antibodies to high-affinity IgE receptor OR to IgE –> mast cell activation

Question 8

What conditions can trigger chronic urticaria? (2)

Answer 8

• Hashimoto’s thyroiditis
• SLE

Question 9

What are drug causes of urticaria? (4)

Answer 9

• aspirin
• penicillins
• NSAIDs
• opiates

Question 10

What could make angio-oedema serious?

Answer 10

Involves face/neck - can compromise airway, requires prompt management

Question 11

What are the clinical features of urticaria? (5)

Answer 11

• erythematous oedematous lesions - pale, pink, smooth raised skin (wheals)
• pruritus
• resolution within 24h
• swelling of face, tongue or lips (40% of urticaria cases associated with angioedema)
• blanching lesions (on palpation)

Question 12

What are the risk factors for urticaria? (5)

Answer 12

• family Hx
• exposure to drug trigger
• exposure to food trigger
• recent insect bite or sting
• recent viral infection

Question 13

What are the first-line investigations for urticaria? (3)

Answer 13

• FBC with differential
• CRP/ESR - normal or raised
• C4 level - decreased in hereditary and acquired angioedema

Question 14

What does FBC with differential show in urticaria?

Answer 14

• eosinophilia: drug-induced
• neutrophilia: urticarial vasculitis

Question 15

When do we do CRP/ESR for urticaria?

Answer 15

If urticarial vasculitis suspected

Question 16

What special tests could we do for urticaria? (2)

Answer 16

• skin prick testing
• allergen avoidance diet - see if it improves

Question 17

What are some differential diagnoses for urticaria? (9)

Answer 17

• anaphylaxis - respiratory symptoms (wheeze), hypotension, N/V, diarrhoea, IM epi
• dermatographism
• atopic dermatitis
• urticarial vasculitis - painful, >24h, residual marks upon resolution, found on biopsy, elevated ESR/CRP
• urticarial pigmentosa - small macules/raised papules vs large wheals, Darier’s sign (urticaria on rub/scratch/stroke)
• systemic mastocytosis
• carcinoid - cutaneous flushing
• contact dermatitis - more confluent and irritated
• papular urticaria (insect bites) - smaller papules >24h

Question 18

How is urticaria diagnosed?

Answer 18

Clinical diagnosis based on history and exam

Question 19

What is key to managing urticaria prophylaxis?

Answer 19

Trigger identification and avoidance

Question 20

What is the 1st-line treatment for acute urticaria?

Answer 20

Antihistamines (e.g. loratadine, cetirizine)

Question 21

How do we manage urticaria that is severe or recurrent?

Answer 21

Systemic corticosteroid (prednisolone)

Question 22

How do we manage acute urticaria with airway involvement?

Answer 22

Adrenaline + airway protection + IV antihistamine (diphenhydramine)

Question 23

How do we manage chronic urticaria?

Answer 23

• treatment of underlying illnesses
• antihistamine
• consider H2 antagonist
• consider systemic corticosteroid
• consider LTRA
• 2nd line: omalizumab
• 3rd line: ciclosporin

Question 24

How do we manage hereditary angioedema?

Answer 24

• C1 esterase inhibitor or ecallantide or icatibant
• 2nd line: FFP

Question 25

What are some complications of urticaria? (3)

Answer 25

- excoriations - sedation (antihistamine side effect) - skin infections

Question 26

What is the prognosis like for urticaria?

Answer 26

Excellent - vast majority of patients response well to therapy with non-sedating antihistamines, and the condition is short-lived