First Aid, Chapter 7 Hypersensitivity Disorders, Urticaria

Question 1

What is the pathology of urticaria? What layer of skin does it involve?What layer does angioedema involve?

Answer 1

Pathologically, urticaria results from the activation of vasoactive mediators, including histamine, leukotriene, and others that lead to dilation and increased permeability of blood vessels and edema in the superficial dermis. Angioedema occurs when these mediators are released in the deep dermis and subcutaneous tissue.

Question 2

What is the prevalence of acute urticaria?

Answer 2

20% of the population.

Question 3

What is the prevalence of chronic urticaria?

Answer 3

1% of the population.

Question 4

What is the typical age of onset of chronic urticaria?

Answer 4

3rd to 5th decades of life

Question 5

What is the average duration of chronic urticaria?

Answer 5

2-5 years

Question 6

What percentage of urticaria patients have angioedema?

Answer 6

40%

Question 7

What categories is chronic urticaria divided into?

Answer 7

• Chronic autoimmune urticaria (40–45%)

- Chronic idiopathic urticaria (55–60%)

Question 8

What are causes of urticaria? Use the mnemonic.

Answer 8

Imagine that urticaria is like raised maps on different parts of skin, “Itching Maps”:

• Infections: Bacterial (including Helicobacter pylori), fungal, viral, and helminthic
• Transfusion reactions
• Chronic idiopathic urticaria -Hereditary diseases: Hereditary angioedema, familial cold urticaria, Muckle-Wells syndrome (amyloidosis with deafness and urticaria)
• Inhalation or contact with allergens
• NSAIDs and/or drug reactions
• Gut: Foods or food additives
• Mastocytosis (systemic): Urticaria pigmentosa and Malignancy
• Autoimmune urticaria
• Physical urticarias: Different types
• Systemic lupus erythematosus and other collagen vascular diseases

Question 9

After ruling out acute urticaria and physical urticarias, how often do you identify etiologies in chronic urticaria?

Answer 9

less than 2% of cases.

Question 10

What is the pathogenesis of CIU?

Answer 10

Pathogenesis of CIU still unclear. More recent studies point to histamine-releasing factors and defects in basophile signaling and/or function.

Question 11

What percentage of CIU patients have thyroid antibodies?

Answer 11

20%

Question 12

What are mediators of urticaria?

Answer 12

• Mast cell: Histamine, prostaglandin D, leukotrienes LTC4 and LTD4, and PAF
• Complement system: Anaphylatoxins C3a, C4a, and C5a; histamine
• Hageman factor-dependent pathway: Bradykinin
• Mononuclear cells: Histamine-releasing factors and chemokines

Question 13

Which cold urticarias do not react to the ice cube test?

Answer 13

Cold urticaria syndromes that have a negative ice cube test: Cold-induced cholinergic urticaria, systemic cold urticaria, and cold-dependent dermographism.

Question 14

How do you differentiate between cholinergic urticaria with hypotension and exercise-induced anaphylaxis?

Answer 14

Cholinergic urticaria can also present with hypotension and look clinically similar to exercise-induced anaphylaxis (EIA). The key difference is that patients with EIA will not react with passive heating.

Question 15

How long do you keep the ice cube on for the ice cube test?

Answer 15

5 min

Question 16

What is the classic treatment for cold induced urticaria?

Answer 16

Cyproheptadine (C for cold)

Question 17

What is the test for local heat urticaria? What is the classic treatment?

Answer 17

Apply water heated to 45°C in a test tube on skin for 5 min, treat with hydroxyzine (H for heat).

Question 18

What percentage of physical urticarias does cholinergic urticaria comprise? What is the characteristic appearance?

Answer 18

~30% of all cases of physical urticaria, characterized by numerous small punctate wheals

Question 19

What is the trigger in cholinergic urticaria?

Answer 19

• Elevation of body temperature (e.g., heat, exercise, emotional stress, spicy foods)
• Autologous sweat sensitivity: Sweat may cause basophil degranulation in sensitive subjects who have positive skin test to own sweat

Question 20

How is cholinergic urticaria tested?

Answer 20

Various Testing Methods:

• Intradermal injection of methacholine
• Have patient ride stationary bike or run on treadmill until point of sweating, then continue for 15 min
• Nonexertional elevation of core body temperature by submerging arm of patient in 42ºC hot water bath until core temp increases ≥1°C

Question 21

What is the trigger in solar urticaria?

Answer 21

Exposure of skin to sunlight (triggering wavelengths vary)

Question 22

What is the test for solar urticaria?

Answer 22

• Simple exposure of patient’s skin to natural sunlight

- Phototesting: Skin is exposed to UVA and UVB of varying wavelengths using a monochromatic light source

Question 23

What is the typical appearance of aquagenic urticaria? What causes it? What is the test for it?

Answer 23

• Small wheals result from contact with water, independent of temperature; salinity of water important in some cases
• Apply 35°C water compress to upper body for 30 min

Question 24

What is the typical presentation of delayed-pressure urticaria/angioedema? What is the test for it?

Answer 24

• Symptoms can develop 30 min to 12 hr after pressure has been applied to skin
• Sling attached to a 10–15 lb weight is placed over arm or shoulder for 15 min. Patient reports response over next 4– 24 hr

Question 25

What skin tests should be done for urticaria?

Answer 25

Blood tests are usually not helpful for determining the cause of acute urticaria. For chronic urticaria without identified etiology, limited or targeted testing may be done for patients who have an otherwise unremarkable history and physical exam. Skin biopsy only if history or physical exam is suggestive of vasculitic process

Question 26

What are typical findings in urticarial vasculitis? What are symptoms? Labs? Histopathology?

Answer 26

Lesions are less pruritic and described as painful or burning, individual hives last >24 hours, leave residual purpura or hyperpigmentation. Elevated erythrocyte sedimentation rate (ESR), arthralgias, myalgias, fever, leukocytosis are common associated abnormalities. Histopathology shows leukocytoclasis and vessel wall damage.

Question 27

What are systemic findings in hypocomplementemic urticarial vasculitis syndrome? What are lab findings?

Answer 27

Urticaria with hypocomplementemia, includes systemic findings such as arthralgias/arthritis, obstructive lung disease, glomerulonephritis, uveitis, angioedema, and recurrent abdominal pain. Laboratory findings include low C3, C4, and C1q, anti-C1q antibodies, and elevated ESR.