The child with recurrent facial swelling and a family airway history — structured encounter

Setting and candidate instructions

You are the paediatric registrar in the outpatient clinic. A ten-year-old boy is referred by his general practitioner for three episodes of painless facial and lip swelling over the past year. Each episode lasted two to three days, occurred without any wheals or itch, and resolved spontaneously. Between attacks he is entirely well. His father, who accompanies him, describes similar episodes in his own childhood and one emergency intubation for throat swelling at the age of twenty. The boy is currently well, with no swelling, no airway symptoms and normal observations. The examiner will ask you to build the differential, choose the pivotal investigation, explain the mechanism, and construct a treatment and disposition plan that protects the airway and addresses the family. [9]

Information released on request

1. On the swelling episodes: non-pitting, non-dependent, not itchy; involve lips, cheeks and periorbital region; last two to three days; occur without wheals; three episodes over twelve months. [9]
2. On family history: father had similar episodes from childhood; intubated once for laryngeal swelling at age twenty; paternal aunt describes recurrent abdominal pain episodes. [10]
3. On the current examination: well, afebrile, normal observations, no current swelling, no urticaria on skin examination, normal abdomen.
4. On medications: no regular medications; no ACE-inhibitor; no NSAID in the lead-up to episodes.

Examiner prompts

1. "What is the most likely diagnosis, and what single feature of the history points you there?" [9]
2. "What is the single most important initial investigation, and why?" [9]
3. "Explain the mechanism to me, and tell me why antihistamines, adrenaline and steroids will not help." [10]
4. "Construct the on-demand and prophylaxis plan for this child." [9]
5. "What do you tell the family about the risk to this child and to other family members?" [10]

Model performance

"The most likely diagnosis is hereditary angioedema. The features that point me there are angioedema occurring without wheals, the non-itchy non-dependent nature of the swelling, the recurrent pattern over a year, and the family history of similar swelling with a documented emergency airway event in the father." [9]

"The single most important initial investigation is a serum C4 level. C4 is low both during and between attacks in hereditary angioedema types I and II, so a single level between attacks is a sensitive screen, and a normal C4 effectively excludes these forms. If the C4 is low, I proceed to C1-inhibitor antigenic and functional assays to confirm and type the disease." [9] [10]

"The mechanism is bradykinin-mediated vascular leak. Deficiency or dysfunction of C1-inhibitor allows unopposed plasma kallikrein activity, which cleaves high-molecular-weight kininogen to generate bradykinin. Bradykinin binds vascular B2 receptors and produces deep-tissue angioedema without itch or wheals. This is fundamentally different from the histamine-driven vasodilation of ordinary urticaria." [10]

"Antihistamines, adrenaline and corticosteroids will not help because they target the histamine pathway — antihistamines block H1 receptors, adrenaline and steroids suppress mast-cell activation — and none of these touch a bradykinin-driven attack. The definitive acute treatments are C1-inhibitor concentrate, either plasma-derived or recombinant, or icatibant, a bradykinin B2-receptor antagonist, given in weight-based paediatric doses." [9] [10]

"For the plan: this child needs an on-demand treatment available at all times — ideally a home supply of C1-inhibitor concentrate or icatibant that a trained caregiver can administer, because airway attacks can progress faster than an ambulance can arrive. He needs a medical-alert device, a written action plan for the family and the school, and education on when to call emergency services. Long-term prophylaxis with lanadelumab, a kallikrein inhibitor, or regular C1-inhibitor concentrate may be appropriate given the airway history in the family, and I would involve the allergy or immunology service to tailor this. I would also screen first-degree relatives, because hereditary angioedema is autosomal dominant and the father's history suggests he is affected." [9]

Marking domains

Disposition and safety-net standard for this encounter

The child is referred to allergy or immunology for confirmation of the diagnosis and long-term co-management. An on-demand treatment plan is established before the child leaves the encounter: a home supply of C1-inhibitor concentrate or icatibant where feasible, a medical-alert device, and a written action plan for the family and the school that names the airway-danger signs (voice change, stridor, drooling, dysphagia) and the immediate action. The family is counselled that hereditary angioedema is autosomal dominant, that the father should be assessed, and that other relatives — including the paternal aunt with abdominal pain episodes — may be affected. The team states that antihistamines, adrenaline and corticosteroids are not definitive for this condition and should not delay the administration of the on-demand treatment. "Return if worried" is not a substitute for any of this. [9] [10]