Derm Cases · Dermatology / Internal Medicine / Paediatrics interface
OSCE — string of pearls blistering on vancomycin: linear IgA bullous dermatosis
An 8-minute OSCE station on recognition of adult and childhood linear IgA bullous dermatosis, vancomycin drug trigger, linear vs granular IgA DIF distinction from dermatitis herpetiformis, dual biopsy strategy, and first-line dapsone after G6PD screening.
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Study tools
Target exams
NEET-PGINICETUSMLEPLABMRCP
Prompt
An 8-minute OSCE station on recognition of adult and childhood linear IgA bullous dermatosis, vancomycin drug trigger, linear vs granular IgA DIF distinction from dermatitis herpetiformis, dual biopsy strategy, and first-line dapsone after G6PD screening.
Brief (to candidate)
A 58-year-old inpatient develops tense bullae on annular urticarial plaques over the lower trunk with a peripheral “string of pearls” of new vesicles, 10 days after starting vancomycin. Mucosa is mildly involved. A paediatric stem (age 3, genital “ring of jewels”) is available if asked. You have 8 minutes to diagnose, plan DIF-guided work-up, stop the culprit, and start first-line therapy safely.
Candidate instructions
- Recognise LABD morphology in adults and the childhood ring of jewels phenotype.
- Identify vancomycin (and other drugs) as key adult triggers.
- Distinguish LABD from BP, DH, pemphigus, EBA on clinical + IF grounds.
- Plan lesional H&E + perilesional DIF.
- Prescribe dapsone only after G6PD check; explain drug-withdrawal pathway for drug-induced disease.
Examiner checklist (mark each domain / 10)
| Domain | Key actions expected |
|---|---|
| Recognition | Tense subepidermal bullae on annular/urticarial plaques; string of pearls edge; childhood ring of jewels (perineum/perioral)[4][5] |
| Drug history | Stops/holds vancomycin (classic culprit); reviews NSAIDs, lithium, ACEI, other antibiotics, checkpoint inhibitors[1] |
| DIF distinction | Linear IgA along BMZ = LABD; granular IgA in dermal papillae = dermatitis herpetiformis (gluten); linear IgG/C3 = BP[2][4] |
| Investigations | Lesional biopsy (subepidermal neutrophil-rich blister) + perilesional DIF; optional salt-split/serology where available[2] |
| First-line Rx | Drug-induced: withdraw culprit (often resolves in 2–6 weeks) ± bridging therapy; idiopathic: dapsone 50–150 mg/day after G6PD[1] |
| Dapsone safety | Baseline G6PD, FBC; monitor haemolysis, methaemoglobinaemia, agranulocytosis, neuropathy, dapsone hypersensitivity |
| Supportive care | Wound care, infection watch, pain, mucosal protection; dermatology follow-up |
Model key actions
- Diagnose vancomycin-associated LABD from morphology + drug chart and stop the drug.[1]
- Confirm with perilesional DIF showing linear IgA, not granular IgA of DH.[2][4]
- Start dapsone after G6PD screening for idiopathic/persistent disease.[1]
Common errors
- Treating as bullous pemphigoid with high-dose steroids without drug review.
- Confusing linear IgA (LABD) with granular IgA (DH) and starting a gluten-free diet only.
- Starting dapsone without G6PD.
- Missing childhood ring of jewels distribution.
- Leaving the patient on vancomycin “because the infection needs it” without seeking an alternative antibiotic.
References5ShowHide
- [1]Caux F, Patsatsi A, Karakioulaki M, et al. S2k guidelines on diagnosis and treatment of linear IgA dermatosis initiated by the European Academy of Dermatology and Venereology (EADV). Journal of the European Academy of Dermatology and Venereology, 2024.PMID 38421060
- [2]van Beek N, Holtsche MM, Atefi I, et al. State-of-the-art diagnosis of autoimmune blistering diseases. Frontiers in Immunology, 2024.PMID 38903493
- [4]Egan CA, Zone JJ. Linear IgA bullous dermatosis. International Journal of Dermatology, 1999.PMID 10583613
- [5]Wang KL, Lehman JS, Davis DMR. Linear IgA bullous dermatosis of childhood: Retrospective single-center cohort. Pediatric Dermatology, 2024.PMID 38378007
- [6]Wojnarowska F, Marsden RA, Bhogal B, Black MM. Chronic bullous disease of childhood, childhood cicatricial pemphigoid, and linear IgA disease of adults. A comparative study demonstrating clinical and immunopathologic overlap J Am Acad Dermatol, 1988.PMID 3056993