Primary Immunodeficiency and Allergic Disorders — WACS Viva & Clinical Scenarios (Rheumatology and Clinical Immunology)

Exam-style primary immunodeficiency and allergic disorders viva scenarios with examiner probes and model answers for Internal Medicine candidates.

Scenarios covered

• SCENARIO 1: A 28-year-old male presents with a history of recurrent bacterial pneumonia, chronic pansinusitis, and persistent non-bloody diarrhoea with malabsorption over the preceding 3 years. Serum immunoglobulin analysis demonstrates an IgG level of 1.8 g/L (reference range 7.0 to 16.0 g/L), with markedly reduced IgA and IgM levels. HIV serology is non-reactive. Formulate the diagnostic criteria required to establish Common Variable Immunodeficiency (CVID), list the secondary causes of hypogammaglobulinaemia that must be systematically excluded, and detail the principles and monitoring of long-term imm
• SCENARIO 2: A 34-year-old female presents to the emergency medical unit with sudden-onset painless swelling of the face, lips, and tongue, accompanied by severe crampy abdominal pain and recurrent vomiting. She has no associated urticaria, pruritus, or history of new dietary or medication exposures. She reports similar recurrent episodes in her maternal uncle. Detail the pathophysiological mechanism of Hereditary Angioedema (HAE), outline the tiered laboratory investigation protocol used to classify HAE types, and contrast the emergency airway and pharmacological management of acute HAE attacks with that
• SCENARIO 3: A 24-year-old female develops sudden-onset generalised urticaria, periorbital oedema, stridor, wheezing, and profound hypotension (blood pressure 70/40 mmHg) within 10 minutes of receiving an intramuscular injection of procaine penicillin. Outline the step-by-step immediate emergency resuscitation algorithm for acute anaphylactic shock, specifying drug dosages, routes, fluid management, indication for second-line agents, and the timing of serum mast cell tryptase sampling for diagnostic confirmation.
• SCENARIO 4: A 38-year-old male living with HIV on first-line antiretroviral therapy and co-trimoxazole preventive therapy presents with high-grade fever, extensive atypical targetoid maculopapular lesions with epidermal detachment involving 25% of the total body surface area, and severe mucosal ulcerations affecting the oral cavity, conjunctivae, and genitalia. Describe the clinical differentiation between Stevens-Johnson Syndrome (SJS), SJS/Toxic Epidermal Necrolysis (TEN) overlap, and TEN, calculate the SCORTEN prognostic score, and outline the critical multi-system supportive and barrier care required
• SCENARIO 5: A 20-year-old male presents with his second episode of invasive Neisseria meningitidis septicaemia within eighteen months. Formulate an immunological diagnostic pathway to identify inherited complement deficiencies, differentiate between classical, alternative, and terminal pathway defects using screening and specialized assays, and specify the long-term antimicrobial and immunisation prophylaxis protocols required for this patient.