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DR13.1-2 | Vesiculobullous Lesions — PBL Case

CLINICAL SETTING

A 68-year-old male farmer, Mr. R, is brought to the district general hospital casualty by his family. His wife reports that for the past 3 months he has had intense itching all over his body — so severe that he could not sleep. Two weeks ago, large water-filled blisters began appearing on his thighs, abdomen, and forearms. The blisters are so tense and firm that he was initially relieved (thinking they would not break), but several have now ruptured, leaving painful sores that are slow to heal. He has no mouth sores. He has not taken any new medications. He was previously healthy except for well-controlled hypertension on amlodipine for 4 years. On general examination: afebrile, BP 136/84 mmHg, pulse 88/min. Skin examination: approximately 30 tense bullae (2–8 cm diameter) on an erythematous urticarial base, distributed over the lower abdomen, bilateral thighs, and forearms. Several have ruptured, with moist erosions and superficial crusting. Oral mucosa is completely clear. Nikolsky sign: negative on perilesional skin. The examining intern asks the attending physician, 'Is this the same disease as the patient in bed 4 who had mouth sores and blisters that popped immediately?'

Trigger 1: Trigger 1 — Initial Presentation: What Disease Are We Dealing With?

The intern notes the following: (a) tense blisters on erythematous base; (b) no mucosal involvement; (c) intense pruritus preceding blister formation; (d) elderly male; (e) Nikolsky sign negative. The patient in bed 4 (mentioned by the intern) had: flaccid blisters, oral erosions preceding skin lesions, and a positive Nikolsky sign.

DISCUSSION POINTS

  • What is your primary diagnosis for Mr. R, and what is the diagnosis of the patient in bed 4? Justify each using the clinical findings.
  • Explain, using the anatomy of the epidermis, why Mr. R's blisters are tense and do NOT rupture spontaneously, while the other patient's blisters are flaccid and rupture easily.
  • Why is Nikolsky sign negative in Mr. R but positive in bed-4 patient? Link your answer to the level of the epidermal split.
  • The intern asks: 'If both patients have autoimmune blistering, why is only one's Nikolsky sign positive?' Teach the intern using the concept of desmosomes vs hemidesmosomes.
Click to reveal Trigger 2: Trigger 2 — Investigations: What Tests Will Confirm This? (discuss previous trigger first!)

Trigger 2: Trigger 2 — Investigations: What Tests Will Confirm This?

The attending requests investigations. Results available the next day: - Routine bloods: Hb 11.2 g/dL, TLC 12,400/μL (eosinophils 22%), serum albumin 3.1 g/dL - Skin biopsy (H&E, from edge of intact blister): subepidermal blister with eosinophilic infiltrate; basal cells intact and lining the blister floor - Direct immunofluorescence (DIF) of perilesional skin: linear deposits of IgG and C3 at the basement membrane zone - Serum ELISA: anti-BP180 antibody titre markedly elevated; anti-desmoglein 1 and 3: undetectable

DISCUSSION POINTS

  • Interpret each investigation result. Which results confirm the diagnosis and which are non-specific?
  • What is the significance of the eosinophilia (blood + biopsy)? What does it tell you about the immunological mechanism in this disease?
  • The DIF shows linear IgG at the basement membrane zone. What structure are the IgG antibodies binding, and why does this produce a subepidermal (rather than intra-epidermal) blister?
  • If this patient's DIF had instead shown intercellular IgG in a chicken-wire pattern throughout the epidermis, what diagnosis would you reconsider? What would the ELISA show in that case?
  • Mr. R's serum albumin is mildly low at 3.1 g/dL. What is the mechanism of this finding in bullous disease, and at what threshold would you become concerned about nutritional compromise?
Click to reveal Trigger 3: Trigger 3 — Management: What Do We Do Now? (discuss previous trigger first!)

Trigger 3: Trigger 3 — Management: What Do We Do Now?

The diagnosis of bullous pemphigoid is confirmed. The registrar plans to start systemic treatment. However, before the specialist dermatologist arrives, the nursing staff reports: three new large bullae have appeared overnight, wound dressings are adhering to skin, and the ward nurse asks the house officer whether to puncture the blisters. Mr. R is in pain; his oral intake is reduced because of discomfort; he has developed fever (38.2°C) over the past 6 hours.

DISCUSSION POINTS

  • Address the nurse's question: should intact blisters be drained? If yes, how — describe the technique. If no, justify why not.
  • The wound dressings are adhering to skin. What type of dressing should be used for a patient with active vesiculobullous disease? Why is standard adhesive tape contraindicated?
  • Outline your complete primary management plan: (a) supportive care for the skin, (b) fluid and nutritional management, (c) pain and symptom control, (d) pharmacological management including the cornerstone drug class and route, and (e) monitoring parameters for drug side effects.
  • Mr. R develops fever. List the two most important causes to exclude and explain how you would differentiate them clinically and with investigations.
  • The specialist asks you to write a referral letter. What are the four essential pieces of information you must include to enable safe handover?
Click to reveal Trigger 4: Trigger 4 — Integration and Reflection: What Lessons Does This Case Teach? (discuss previous trigger first!)

Trigger 4: Trigger 4 — Integration and Reflection: What Lessons Does This Case Teach?

One week later, Mr. R is under dermatology care and has responded well to systemic corticosteroids. However, his fasting blood glucose is 210 mg/dL, he reports pain in both knees, and the ophthalmology clinic has detected early posterior subcapsular cataracts. His wife asks the ward doctor: 'He got these problems from the medicine, didn't he? Was there no other option?'

DISCUSSION POINTS

  • Identify and explain three steroid-related complications evident in Mr. R, and link each to the pharmacological mechanism of corticosteroids.
  • The wife asks whether the disease itself could have been managed without steroids. Describe the steroid-sparing agents that are used in bullous pemphigoid and their mechanism of action (no more than 2 agents, Year-2 level).
  • Reflecting on this case: construct a comparison table between pemphigus vulgaris and bullous pemphigoid covering: (a) age group, (b) type of blister, (c) mucosal involvement, (d) Nikolsky sign, (e) histology, (f) DIF pattern, (g) target antigen, and (h) prognosis without treatment. Ensure no directional error in any field.
  • A junior student asks: 'Both diseases are autoimmune — can't we just check the blood test (ELISA) and skip the biopsy?' How would you respond, citing the strengths and limitations of ELISA alone for the diagnosis of autoimmune vesiculobullous disease?