Bullous Dermatoses and Cutaneous Drug Reactions — WACS Viva & Clinical Scenarios (Dermatology and Venereology)

Exam-style bullous dermatoses and cutaneous drug reactions viva scenarios with examiner probes and model answers for Internal Medicine candidates.

Scenarios covered

• SCENARIO 1: A 42-year-old patient presents with painful oral erosions preceding the eruption of widespread, flaccid bullae on normal-appearing skin that rupture easily, leaving raw, denuded areas. A bedside lateral pressure test on perilesional skin causes epidermal detachment. Outline the immediate clinical differential diagnosis, diagnostic evaluation (including histopathology and direct immunofluorescence), and distinguishing features separating intraepidermal from subepidermal blistering disorders.
• SCENARIO 2: A 28-year-old woman living with HIV and newly commenced on cotrimoxazole and efavirenz-based antiretroviral therapy presents with fever, malaise, diffuse dusky erythematous macules, atypical targetoid lesions, and sheet-like epidermal detachment involving 25% of her total body surface area, alongside extensive hemorrhagic oral, ocular, and genital mucosal ulcerations. Discuss the diagnostic classification (SJS vs SJS/TEN overlap vs TEN), calculate the SCORTEN prognostic score, identify regional high-risk culprit drugs, and detail the emergency critical-care and barrier-nursing management plan.
• SCENARIO 3: A 55-year-old man presenting with facial oedema, high-grade fever, diffuse morbilliform exanthem, generalized lymphadenopathy, and jaundice 4 weeks after starting allopurinol for chronic gout. Formulate the diagnostic evaluation using validated criteria (e.g., RegiSCAR), describe systemic organ manifestations, outline monitoring parameters, and discuss evidence-based therapeutic interventions.
• SCENARIO 4: Demonstrate the step-by-step procedural technique and diagnostic utility of the Tzanck smear, Nikolsky sign, and skin punch biopsy protocol (formalin-fixed versus Michel medium) in blistering dermatoses. Compare the pathophysiologic cleavage plane, clinical presentation, and management of Staphylococcal Scalded Skin Syndrome (SSSS) against Toxic Epidermal Necrolysis (TEN).
• SCENARIO 5: A 60-year-old patient diagnosed with severe pemphigus vulgaris with extensive mucocutaneous involvement fails to achieve disease control on high-dose oral prednisolone monotherapy. Formulate an evidence-based immunosuppressive treatment strategy, including steroid-sparing agents (e.g., azathioprine, mycophenolate mofetil) and targeted biological therapies (e.g., rituximab), outlining pre-treatment screening, dosing protocols, infection prophylaxis, and monitoring for adverse effects.