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DR14.1-3 | Urticaria Angioedema — PBL Case

CLINICAL SETTING

You are a final-year MBBS student in a district hospital casualty department. It is 9 pm on a Wednesday. The duty dermatology intern asks you to assist with two consecutive patients who have been triaged together because the nursing staff labelled both as 'allergic rash'. Your task is to assess each patient systematically and decide what to do.

Trigger 1: Patient A: The Man with Hives for Three Months

Mr Suresh, 38, a software engineer, walks in looking irritated rather than unwell. He has widespread itchy wheals over his trunk and limbs, each lasting about 4 hours before fading completely without any marks. He has been having these episodes daily for 3 months. He has tried various antihistamines from pharmacies, mostly old-generation tablets, with only partial relief. He has no fever, no joint pains, no new drug exposures, no consistent food trigger, and no family history of angioedema. His vital signs are: BP 124/78, HR 82, RR 14, SpO₂ 99%. Examination reveals multiple urticarial plaques; no lymphadenopathy, no hepatosplenomegaly. He says: 'I have tried three different antihistamines — why isn't this getting better?'

DISCUSSION POINTS

  • Classify Mr Suresh's urticaria using the EAACI two-axis system. Justify every decision with information from his presentation. What single additional history item, if positive, would change your classification from 'spontaneous' to 'inducible'?
  • Mr Suresh says the pharmacy tablets make him 'foggy'. Explain the pharmacological basis for this complaint and describe what you would prescribe instead, with dose, timing, and a realistic expected timeline for response.
  • His previous doctor ordered 30 blood tests including a food allergen panel (RAST) at significant cost. Critically evaluate this investigation strategy. Which investigations are guideline-recommended and which are not, and why?
  • Mr Suresh asks: 'Will I have this forever?' What is the natural history of chronic spontaneous urticaria and how would you counsel him about prognosis and the importance of treatment adherence?
Click to reveal Trigger 2: Patient B: The Woman Whose Tongue is Swelling (discuss previous trigger first!)

Trigger 2: Patient B: The Woman Whose Tongue is Swelling

Mrs Nalini, 45, is brought in urgently from the waiting area. The triage nurse calls you immediately. Mrs Nalini is visibly distressed and pointing to her throat. Her tongue is swollen, her lips are puffy, and she is drooling slightly. There are NO wheals on her skin. She is alert and can speak in short sentences but says her throat feels 'tight'. BP 96/60, HR 118, RR 22, SpO₂ 96% on room air. Her husband says she took a tablet of 'some blood pressure medicine' yesterday — he shows you a strip of ramipril 5 mg prescribed 2 weeks ago. She has never had anything like this before.

DISCUSSION POINTS

  • What is your immediate priority assessment, and what two clinical signs would tell you that this patient is crossing from angioedema to a life-threatening emergency requiring adrenaline RIGHT NOW?
  • Mrs Nalini's husband insists on giving her the 'allergy tablet' (cetirizine) he has in his bag. Explain to him precisely why this will not work for his wife's current problem, using the mechanism of ACE-inhibitor-induced angioedema. What is the definitive treatment of the acute episode and the long-term management change?
  • Compare the three main mechanisms of angioedema: (a) histaminergic (mast-cell-mediated), (b) ACE-inhibitor-induced bradykinin excess, and (c) hereditary angioedema due to C1-INH deficiency. For each: the mediator responsible, the expected response to antihistamines, and the key investigation that distinguishes it.
  • After Mrs Nalini is stabilised, her cardiologist asks if they can restart an ACE inhibitor because 'she still needs the blood pressure control'. How would you advise? What antihypertensive class is NOT associated with bradykinin-mediated angioedema and why?
Click to reveal Trigger 3: The Registrar's Teaching Round: Dermographism Demonstration (discuss previous trigger first!)

Trigger 3: The Registrar's Teaching Round: Dermographism Demonstration

The next morning, the dermatology registrar calls a bedside teaching session. A consenting patient, Mr Arjun, 29, has been admitted for evaluation of 'writing on skin'. He reports that wherever clothing rubs or his skin is scratched, a raised, itchy, linear welt appears within minutes. He finds it embarrassing and it wakes him at night. The registrar asks you to perform and interpret the dermographism test under supervision.

DISCUSSION POINTS

  • Describe step-by-step how you would perform the dermographism test on Mr Arjun: site, instrument, force, timing, and what you are observing at each step. What is the triple response of Lewis and which component of it confirms that the result is symptomatic rather than physiological?
  • The test produces a clear pruritic linear wheal. Classify Mr Arjun's condition using the full urticaria classification framework. Explain why his condition is classified as 'inducible' rather than 'spontaneous' and what this means for his investigation and management.
  • Mr Arjun asks whether he needs to avoid certain activities or environments. What lifestyle modifications would you advise specifically for symptomatic dermographism? Would his treatment ladder differ from Mr Suresh's chronic spontaneous urticaria, and why?
  • The registrar asks you to compare dermographism with two other physical urticarias: cold urticaria and cholinergic urticaria. For each, state the trigger, the diagnostic test, and one specific safety counselling point that is unique to that condition.
Click to reveal Trigger 4: Integration: The Three Patients and the Common Thread (discuss previous trigger first!)

Trigger 4: Integration: The Three Patients and the Common Thread

At the end of the session, the registrar asks you to stand back and synthesise what you have learned from all three patients. She presents a summary table on the board with three columns — one for each patient — and asks you to fill in the rows.

DISCUSSION POINTS

  • For each of the three patients (Mr Suresh, Mrs Nalini, Mr Arjun), state: (a) the classification, (b) the dominant mediator (histamine, bradykinin, or histamine with a defined physical trigger), (c) the first-line treatment, and (d) the most dangerous error to avoid. Present this as a comparative table in your discussion.
  • The registrar asks: 'What is the single clinical skill — history or examination — that would have correctly triaged all three patients without any blood tests or investigations?' Defend your answer with evidence from each case.
  • A fourth patient is mentioned: a 16-year-old girl with recurrent isolated angioedema (no wheals), a low C4 between attacks, positive family history, and no drug exposure. Where does she fit in the schema you have constructed? What additional investigation would confirm her diagnosis, and why is antihistamine treatment futile in her case?
  • The registrar closes with: 'What does the management of urticaria tell us about the relationship between pathogenesis and therapy?' Construct a brief argument (3–4 sentences) that uses evidence from all three patients to answer this question — connecting mediator identity to treatment selection and why that connection is clinically critical.