A 26-year-old woman presents with recurrent crops of typical target lesions on the dorsal hands and elbows, appearing 10 days after each episode of herpes labialis. She has had 8 episodes in the past 18 months, each causing significant distress and functional impairment. Mucosal involvement is limited to a few oral aphthae. Histology confirms interface dermatitis with apoptotic keratinocytes. The diagnosis is erythema multiforme minor with HSV-1 as the identified trigger.
Which of the following management options, marked **B** in the diagram, is the cornerstone of long-term prophylaxis for this patient's recurrent disease?
A. Acyclovir 400 mg twice daily for 6–12 months
B. Symptomatic care alone with antihistamines and topical steroids
C. Lifelong oral cyclosporine monotherapy
D. High-dose IV methylprednisolone and burn unit assessment
Explanation
Why Acyclovir 400 mg twice daily for 6–12 months is right
The clinical anchor is HSV suppression as the cornerstone of recurrent EM management. In recurrent erythema multiforme minor (≥6 episodes/year or distressing flares), acyclovir 400 mg twice daily is the first-line prophylactic agent, supported by the Tatnall RCT (BJD 1995) and BAD EM Guidelines 2016. HSV is the underlying driver in over 70% of recurrent EM cases, even when an HSV trigger is not clinically apparent each time. The mechanism is prevention of viral reactivation and delivery of HSV DNA to keratinocytes, thereby interrupting the CD4 Th1–mediated delayed-type hypersensitivity cascade that leads to keratinocyte apoptosis and target lesion formation. A 6–12 month course is standard; alternatives include valacyclovir 500 mg/day or famciclovir 250 mg BD.
Why each distractor is wrong
High-dose IV methylprednisolone and burn unit assessment: This is appropriate for erythema multiforme major with severe mucosal involvement or for toxic epidermal necrolysis (TEN), not for recurrent EM minor. Systemic corticosteroids are explicitly avoided in recurrent EM because they may prolong viral shedding and increase recurrence frequency.
Lifelong oral cyclosporine monotherapy: Cyclosporine is reserved for patients who fail antiviral suppression (i.e., those who continue to have ≥6 flares/year despite acyclovir). It is not first-line and is not given lifelong as monotherapy in EM minor.
Symptomatic care alone with antihistamines and topical steroids: This is appropriate for a single self-limited episode of EM minor. However, in recurrent disease (8 episodes in 18 months), symptomatic care alone does not address the underlying HSV-driven pathogenesis and will not prevent future flares.
High-YieldNEET PG
Recurrent EM minor = HSV suppression with acyclovir 400 mg BD; avoid systemic steroids (prolong shedding); reserve cyclosporine/MMF for antiviral failures.
BAD EM Guidelines 2016; Rook's Textbook of Dermatology 10e; Tatnall, BJD 1995
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