Page 10 of 12
DR14.1-3 | Urticaria Angioedema — Graded Quiz
Click any question card to reveal the correct answer.
A 35-year-old woman is brought to the emergency department with sudden onset breathlessness, stridor, and swelling of the tongue following a bee sting 20 minutes ago. Her blood pressure is 80/50 mmHg. Which is the SINGLE MOST URGENT intervention?
Correct. Anaphylaxis (stridor + hypotension + angioedema post-sting) mandates immediate IM adrenaline 0.5 mg (1:1000) into the anterolateral thigh. This is the only intervention that reverses all limbs of the anaphylactic response simultaneously.
Anaphylaxis with airway compromise and hypotension: IM adrenaline is first-line and life-saving. No other drug should precede it. The most dangerous error is reaching for an antihistamine or steroid instead.
This is anaphylaxis — life-threatening. Antihistamines have no effect on hypotension or bronchospasm in anaphylaxis. Steroids have a 4–6-hour onset and cannot reverse acute airway compromise. Only adrenaline addresses all three limbs simultaneously.
Click to reveal answer
A 50-year-old man has had recurrent isolated episodes of lip and tongue swelling (no wheals, no urticaria) for 6 months. He takes ramipril 5 mg daily for hypertension. C4 is persistently low between attacks. C1-esterase inhibitor antigen and function are reduced. His father had similar episodes. Which diagnosis is most likely?
Correct. Persistently low C4 between attacks, reduced C1-INH antigen and function, family history, and recurrent isolated angioedema (no wheals) are diagnostic of hereditary angioedema Type I. While ACE inhibitors can also cause angioedema, they do not deplete complement or C1-INH.
Hereditary angioedema: recurrent isolated angioedema (no wheals), family history, low C4 (always low, even between attacks), reduced C1-INH antigen and function. ACE-inhibitor angioedema has normal complement; allergic angioedema has wheals and normal complement; CSU with angioedema has wheals.
Integrate all the data: the persistently low C4 between attacks and the family history point beyond a drug-only explanation. ACE-inhibitor angioedema does NOT consume C4 or C1-INH. Low C4 with reduced C1-INH antigen/function = complement pathway activation = hereditary angioedema.
Click to reveal answer
A 22-year-old nursing student develops small (2–3 mm), intensely itchy, punctate wheals over her trunk and arms each time she exercises in the gym. The wheals appear within 15 minutes and resolve within an hour. Cold exposure does not provoke them. The MOST LIKELY diagnosis is:
Correct. The hallmarks of cholinergic urticaria are small (2–3 mm) punctate wheals triggered by exercise, sweating, hot baths, or emotional stress (stimuli that raise core body temperature), with rapid onset and resolution. Cold exposure is explicitly negative here.
Cholinergic urticaria: small (2–3 mm) punctate wheals, triggered by heat/exercise/sweating/hot bath; transient. Dermographism = linear from friction; cold urticaria = cold-triggered; pressure urticaria = delayed (hours after pressure).
Match the trigger to the urticaria type. Each inducible urticaria has a characteristic provoking stimulus: exercise/heat/sweating → cholinergic; friction/stroking → dermographism; cold → cold urticaria; sustained pressure (delayed) → pressure urticaria.
Click to reveal answer
You are reviewing investigations in a 40-year-old woman with confirmed chronic spontaneous urticaria of 4 months' duration. She has no systemic symptoms, no lymphadenopathy, and no skin findings suggestive of vasculitis. Which investigation strategy is most appropriate?
Correct. Guidelines recommend a limited targeted screen for chronic urticaria without systemic features: CBC, ESR or CRP, and thyroid function. Additional tests (ANA, anti-dsDNA, H. pylori, ASST) are added only when the history suggests a specific cause. Comprehensive allergen panels rarely alter management and are not recommended routinely.
Chronic urticaria investigations should be targeted and stepwise: basic screen (CBC, ESR, TFT) ± thyroid antibodies; NOT comprehensive allergy panels (positive IgE rarely changes management). Biopsy is reserved for lesions lasting >24 h with residual marks (suspect vasculitis).
Resist the urge to over-investigate. In chronic urticaria, an extensive allergy panel almost never identifies a relevant allergen that changes management. The correct approach is stepwise: basic screen first, then history-directed additional tests.
Click to reveal answer
A 3-year-old child develops hives and perioral swelling 15 minutes after eating peanuts for the first time. She has no previous history of urticaria. How would you classify this urticaria?
Correct. This is acute (first episode, clearly <6 weeks) spontaneous urticaria in the context of IgE-mediated peanut allergy. The classification of 'inducible' refers specifically to physical stimuli (cold, pressure, heat, dermographism), not to food or drug triggers.
Acute urticaria = duration <6 weeks; spontaneous subtype (even though a food trigger is identified, this is classified as acute spontaneous, not inducible — 'inducible' refers to physical stimuli like cold/heat/pressure/friction, not food/drugs).
Remember: 'inducible urticaria' in the EAACI classification specifically means physical inducible urticaria (cold, heat, pressure, friction, etc.). Food and drug triggers cause spontaneous-type urticaria (acute or chronic). Apply the duration axis: this child has had one episode, so it is acute.
Click to reveal answer
In performing the dermographism test, you stroke the patient's volar forearm firmly with a tongue depressor and observe the following sequence: within 10 seconds a red line appears, followed by a surrounding flare, and then by a 3 mm raised linear wheal. The patient says the line feels itchy. The best interpretation is:
Correct. The sequence described — red line, flare, raised wheal — is the triple response, but the presence of pruritus makes this symptomatic dermographism (not merely physiological). If episodes have been present for ≥6 weeks, this is classified as chronic inducible urticaria.
Symptomatic dermographism: itchy linear wheal following firm stroking = positive test. If present ≥6 weeks, classify as chronic inducible urticaria (dermographism subtype), NOT pressure urticaria. Pruritus distinguishes symptomatic from physiological (simple/factitious) dermographism.
The triple response of Lewis (red line, flare, wheal) is physiological; the itch is what makes it symptomatic dermographism. Apply the classification: if this has been happening for ≥6 weeks and is provoked by skin stroking/friction, it is chronic inducible urticaria — dermographism subtype, not pressure urticaria.
Click to reveal answer
A patient presents with recurrent urticaria. On history, you find that cold exposure triggers discrete wheals. You perform an ice cube test: you apply an ice cube to the volar forearm for 5 minutes, remove it, and after 10 minutes observe a wheal at the test site. You wish to counsel the patient about the most serious risk from their condition. Which is it?
Correct. Cold urticaria carries a risk of anaphylaxis with whole-body cold exposure (e.g., swimming in cold water, cold shower). This can be life-threatening. Patients should be counselled to avoid swimming in cold water, carry an adrenaline auto-injector, and take prophylactic antihistamines before unavoidable cold exposure.
Cold urticaria: positive ice-cube test (wheal on rewarming). Key danger: systemic cold exposure (swimming, cold drink) can trigger generalised urticaria and anaphylaxis — potentially fatal. Patients must carry adrenaline auto-injector and avoid swimming in cold water.
Cold urticaria, while often perceived as merely annoying, carries a real risk of anaphylaxis when large body surface areas are exposed to cold simultaneously (e.g., swimming). Think about what happens when massive mast-cell degranulation occurs across the whole skin.
Click to reveal answer
A 28-year-old woman with chronic spontaneous urticaria is controlled on cetirizine 10 mg once daily. She is now 8 weeks pregnant. Which management change is most appropriate?
Correct. Cetirizine and loratadine have the most reassuring safety data in pregnancy among second-generation antihistamines and are considered the agents of choice. Complete drug withdrawal risks uncontrolled urticaria. Omalizumab lacks adequate pregnancy safety data.
In pregnancy, second-generation antihistamines (cetirizine, loratadine) are generally considered acceptably safe (Pregnancy Category B/C with reassuring observational data). Omalizumab data in pregnancy are limited. Corticosteroids carry teratogenic risk in first trimester. Management should use the lowest effective dose of the safest agent.
Apply the principle of using the safest effective treatment in pregnancy. Among urticaria treatments, second-generation antihistamines (cetirizine, loratadine) have the most observational safety data in pregnancy. Consider the relative unknowns of omalizumab in early pregnancy and the risks of corticosteroids.
Click to reveal answer
A patient with urticaria asks why their doctor prescribed a 'non-drowsy' antihistamine instead of 'the strong one'. You explain the difference. Which property best explains why second-generation H1-antihistamines are preferred in chronic urticaria?
Correct. Second-generation agents (cetirizine, fexofenadine, loratadine, etc.) are highly lipophobic and do not cross the blood–brain barrier readily, causing minimal CNS effects while achieving effective peripheral H1 blockade at the skin.
Second-generation antihistamines are highly lipophobic and do not cross the blood–brain barrier significantly, so they produce peripheral H1 blockade without sedation or cognitive impairment. Their peripheral H1 affinity is similar to or greater than first-generation agents.
The key pharmacokinetic property is CNS penetration. First-generation antihistamines are lipophilic and readily cross the blood–brain barrier, causing sedation and cognitive impairment. Second-generation agents are designed to be lipophobic, avoiding CNS effects while maintaining peripheral efficacy.
Click to reveal answer
A medical student is asked to distinguish an angioedema episode from a wheal of urticaria at the bedside. Which is the most reliable distinguishing feature?
Correct. Angioedema involves deeper tissues (deep dermis, subcutis), so it is poorly demarcated, less intensely pruritic (burning/tightness more common), and typically resolves over a longer period (hours to 72 hours) compared to urticaria wheals (<24 hours). Both can coexist.
Wheal = superficial dermal oedema, well-defined, intensely itchy, resolves <24h. Angioedema = deeper dermis and subcutaneous tissue, poorly demarcated, burning/discomfort rather than itch, resolves over hours to days (usually slower than wheals). Both are transient and leave no scarring.
Think about the depth of the pathological process. Urticaria is superficial dermal oedema; angioedema is the same process in the deeper dermis and subcutis. How does depth affect the clinical presentation — edge definition, itch quality, and time to resolution?
Click to reveal answer