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Year 3 > Urticaria (DERM) > Flashcards

Urticaria (DERM) Flashcards

1
Q

Define urticaria.

A

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

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2
Q

How long does urticaria typically last?

A

<24 hours and leaves no residual skin markings upon resolution

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3
Q

What are some episodes of urticaria associated with?

A

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)

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4
Q

What is the difference between acute and chronic urticaria?

A
  • 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
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5
Q

What is the aetiology of urticaria?

A
  • caused by activation of mast cells in the skin –> release of histamines
  • cytokine release –> capillary leakage –> skin swelling and vasodilation –> erythematous appearance
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6
Q

What is acute urticaria triggered by? (3)

A
  • mainly allergy related (food and drugs) = IgE mediated; direct mast cell degranulation
  • insect bites, contact with allergens
  • viral infections (non-IgE mediated mechanisms)
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7
Q

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

A
  • 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

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8
Q

What conditions can trigger chronic urticaria? (2)

A
  • Hashimoto’s thyroiditis
  • SLE
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9
Q

What are drug causes of urticaria? (4)

A
  • aspirin
  • penicillins
  • NSAIDs
  • opiates
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10
Q

What could make angio-oedema serious?

A

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

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11
Q

What are the clinical features of urticaria? (5)

A
  • 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)
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12
Q

What are the risk factors for urticaria? (5)

A
  • family Hx
  • exposure to drug trigger
  • exposure to food trigger
  • recent insect bite or sting
  • recent viral infection
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13
Q

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

A
  • FBC with differential
  • CRP/ESR - normal or raised
  • C4 level - decreased in hereditary and acquired angioedema
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14
Q

What does FBC with differential show in urticaria?

A
  • eosinophilia: drug-induced
  • neutrophilia: urticarial vasculitis
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15
Q

When do we do CRP/ESR for urticaria?

A

If urticarial vasculitis suspected

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16
Q

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

A
  • skin prick testing
  • allergen avoidance diet - see if it improves
17
Q

What are some differential diagnoses for urticaria? (9)

A
  • 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
18
Q

How is urticaria diagnosed?

A

Clinical diagnosis based on history and exam

19
Q

What is key to managing urticaria prophylaxis?

A

Trigger identification and avoidance

20
Q

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

A

Antihistamines (e.g. loratadine, cetirizine)

21
Q

How do we manage urticaria that is severe or recurrent?

A

Systemic corticosteroid (prednisolone)

22
Q

How do we manage acute urticaria with airway involvement?

A

Adrenaline + airway protection + IV antihistamine (diphenhydramine)

23
Q

How do we manage chronic urticaria?

A
  • treatment of underlying illnesses
  • antihistamine
  • consider H2 antagonist
  • consider systemic corticosteroid
  • consider LTRA
  • 2nd line: omalizumab
  • 3rd line: ciclosporin
24
Q

How do we manage hereditary angioedema?

A
  • C1 esterase inhibitor or ecallantide or icatibant
  • 2nd line: FFP
25
Q

What are some complications of urticaria? (3)

A
  • excoriations
  • sedation (antihistamine side effect)
  • skin infections
26
Q

What is the prognosis like for urticaria?

A

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

Year 3 (145 decks)

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