Vesiculobullous Diseases
Erythema Multiforme
aka EM · Erythema Multiforme Minor/Major
Acute, self-limiting mucocutaneous hypersensitivity reaction commonly triggered by HSV or drugs, with target lesions and haemorrhagic oral crusting.
Trigger
HSV (recurrent) / drugs
Skin
Target lesions
Course
Self-limiting 2-6 weeks
§ overviewOverview
Immune-mediated reaction pattern causing mucocutaneous blistering, often recurrent.
§ icdICD Classification
L51
§ etiologyEtiology
- 01HSV (>70% of recurrent EM)
- 02Mycoplasma pneumoniae
- 03Drugs (sulfonamides, NSAIDs, anticonvulsants)
§ epidemiologyEpidemiology
Young adults (20–40). M > F.
§ pathogenesisPathogenesis
Cell-mediated immune response to viral antigens deposited in keratinocytes → apoptosis and blistering.
§ clinicalClinical Features
- 01Oral: haemorrhagic crusting of lips, erosions on buccal/labial mucosa
- 02Skin: target (iris) lesions — central vesicle, pale ring, erythematous halo
- 03Acute onset, self-limiting 2–6 weeks
- 04Recurrences common if HSV-associated
§ differentialDifferential Diagnosis
- 01Pemphigus vulgaris
- 02SJS/TEN
- 03Primary herpes
- 04Aphthous stomatitis
§ histopathHistopathology
- 01Interface dermatitis
- 02Keratinocyte apoptosis
- 03Lymphocytic infiltrate at DEJ
§ investigationsInvestigations
- 01Clinical diagnosis
- 02Skin biopsy if atypical
- 03HSV PCR if recurrent
§ classificationClassification
- 01EM minor: skin ± oral, no systemic symptoms
- 02EM major: more extensive, systemic symptoms
- 03SJS/TEN: now considered separate spectrum
§ treatmentTreatment
- 01Supportive: hydration, soft diet, analgesics
- 02Topical steroids for oral lesions
- 03Aciclovir prophylaxis for HSV-associated recurrent EM
- 04Systemic steroids controversial
§ complicationsComplications
- 01Dehydration
- 02Secondary infection
- 03Scarring (rare)
§ prognosisPrognosis
Excellent; self-limiting but may recur.
§ examKey Examination Points
- 01Target lesions on skin
- 02Haemorrhagic lip crusting
- 03HSV is main trigger
§ revisionQuick Revision Summary
- 01HSV trigger > drugs
- 02Target lesions
- 03Self-limiting 2-6 weeks
§ vivaBDS Viva Questions
- 01What is the histology of EM?
- 02Differentiate EM from SJS.
- 03How do you prevent recurrence?
§ mcqsMCQs — Assessment (3)
Question 1
Most common trigger for recurrent EM:
Question 2
Characteristic skin lesion:
Question 3
Prevention of HSV-associated recurrent EM:
References
- Neville BW. Oral & Maxillofacial Pathology, 4e
- Scully C. Oral Medicine, 2e
Draft — pending faculty review. Educational use only; verify against current guidelines and primary sources before clinical application.