Urticaria (acute, chronic)

Question 1

Define urticaria.

Answer 1

Urticaria (also called hives) are erythematous, blanching, oedematous, non-painful, pruritic lesions that typically last less than 24 hours and leave no residual markings upon resolution.

Question 2

What % of urticaria is associated with angio-oedema?

Answer 2

Approximately 40% of episodes of urticaria have associated angio-oedema. Angio-oedema is swelling involving the deeper layers of the sub-dermis and can occur in both the acute and chronic setting.

Question 3

How common is urticaria?

Answer 3

• Lifetime incidence of acute urticaria is 20%
• 30% will go on to have prolonged symptoms
• Acute urticaria is more common in children and adolescents
• Chronic urticaria typically affects adults (and women are more affected 1.5:1)
• ACE-i related angio-oedema is more common in black ethnic groups

Question 4

What is the difference between acute and chronic urticaria?

Answer 4

Acute - Episodes that occur over a period of <6 weeks are generally considered acute, can be caused by a specific stimulus (usually hypersensitivity reaction), and are self-limiting.

Chronic - Episodes of hives that occur daily or almost daily over a period of >6 weeks are classified as chronic and appear to be “spontaneous”. They have a complex aetiology.

Question 5

What is a common cause of acute urticaria in children?

Answer 5

Hypersensitivity reaction or underlying viral infections are a common cause of acute urticaria, particularly in children.

Question 6

Summarise briefly the differences in investigations/management of acute and chronic urticaria.

Answer 6

Acute

• Self resolving
• Diagnosis based on history and physical examination
• Antihistamines are mainstay therapy

Chronic

• Diagnosis may require laboratory testing, depending on history
• Referral to a specialist may be needed
• Antihistamines are mainstay therapy

*For those who don’t respond to mainstay therapy options include omalizumab and immunomodulatory medications.

Question 7

Angio-oedema in which locations is dangerous?

Answer 7

Angio-oedema involving the face or neck can potentially compromise the airway and requires prompt airway management

Question 8

What is the pathophysiology of urticaria?

Answer 8

MAST cells are tfound everywhere including in dermis, sub-dermis, mucosal surfaces

• Soluble antigen (IgE mediated) –> mast cell activation –> degranulation –> release of vasoactive mediators including histamine, leukotriene C4, prostaglandin D2
• Vasoactive mediators –> 1) vasodilation, 2) increased vascular permeability –> oedema and pruritus
• Delayed release of cytokines (TNF, IL-4, IL-5) causes longer-lasting lesions

Biopsies of lesions contain CD4+ lymphocytes, eosinophils, basophils and neutrophils and sometimes immune complex depoosition

Urticaria is confined to the DERMAL layer; angio-oedema involves the SUB-DERMAL and MUCOSAL sites

Question 9

What type of hypersensitivity reaction is urticaria? Which immunoglobulins are involved? What is the antigen?

Answer 9

• This is a type 1 hypersensitivity reaction
• IgE mediated
• Soluble antigen

Question 10

What are the risk factors for urticaria?

Answer 10

• FH
• Exposure to trigger (drug/food)
• Recent viral infection - in children; non-IgE
• Insect bite
• Female sex

Question 11

What are the most common causes of acute urticaria?

Answer 11

Allergy (IgE mediated reaction)

• Drugs - penicilins, sulfonamides, muscle relaxants, diuretics, NSAIDs
• Foods - milk, eggs, peanuts, tree nute, finfish, shell fish
• Insect bites

Other (non-IgE mediated mechanisms)

• Drugs - NSAIDs, opioids, vancomycin
• Radiocontrast dye
• Acute viral infection (in children)

Question 12

What are the most common causes of chronic urticaria?

Answer 12

• 40% are thought to be autoimmune causes - IgG autoantibodies to high-affinity receptor for IgE or thyroid antibodies
• Idiopathic
• Strong emotional situations

Only 10% of those with chronic urticaria have an identifiable cause.

Question 13

What are the clinical features of urticaria?

Answer 13

• Erythematouc oedematous lesions
• Pruritus
• Resolution in 24hrs with no residual markings
• Swelling of face, tongue, lips
• Blanching lesions (non-blanching = vasculitis)
• Stridor - if severe laryngeal angio-oedema causing airway obstruction

Question 14

What investigations would you do for urticaria?

Answer 14

• Usually diagnosed from history and physical examination
• Ask patient to keep a food diary if suspected trigger is food then re-introduce slowly.

Consider these for chronic urticaria:

• FBC with differential
• Complete metabolic panel
• Urinalysis - renal dysfunction in vasculitis -> proteinuria and WBC
• ESR and CRP - raised
• IgE receptor antibody and related tests - +ve in AI related chronic U
• TSH
• Antithyroid antibody - Hashimoto’s thyroiditis
• ANA - rheumatological conditions
• Skin biopsy - check for vasculitis
• C4 lecels - low in angio-oedema
• C1-esterase inhibitor level or function - low in hereditary AO
• C1q levels - low levels in acquired angio-oedema (normal in hereditary)

Question 15

How do you manage urticaria?

Answer 15

1. Trigger identification and avoidance
2. H1 receptor antagonists (antihistamines) e.g. cetirizine or loratadine
3. Systemic corticosteroids - if severe
4. Adrenaline (0.3mg IM every 1-2hrs as required) - if severe or causing airway compromise