Thanks to Kenny and Chloe for bringing a case earlier this week to ID report of a woman with an HSV infection who had a rash that was either leukocytoclastic vasculitis, erythema multiforme, or maybe both.
Some pearls about EM, something we see rarely in in the inpatient setting.
What is EM?
- classically a targetoid rash with mucosal involvement. Has a benign clinic course.
- Called “multiforme” because the rash has protean manifestations. But it classically looks like this:
- Rare, most common in children and adults age 20-40.
- Some more pictures of classic lesions
What causes EM?
- most commonly HSV-related.
- rash begins 2-17 days after HSV outbreak
- recurrent EM is usually HSV-related.
- Other causes
- mycoplasma (and other bacterial infections but mycoplasma is common)
- other viruses
- autoimmune disease
SJS vs EM
- Because of the mucosal involvement, it is important to distinguish EM from it’s more life threatening cousin – SJS. Here are some distinguishing feature
- SJS can atypically have target lesions. The targets of EM are papular, while the targets of SJS are macular
- Medications rarely cause EM and commonly cause SJS
- skin sloughing should always make you concerned for SJS
- Other things on the ddx for targetoid skin lesions
- urticaria and urticarial vasculitis
- fixed drug eruption
- bullous pemphigoid
- sweets syndrome
- Rowell syndrome (EM in the setting of cutaneous lupus)
- cutaneous small vessel vasculitis.
- Antivirals are helpful if started early in the course of an HSV-mediated outbreak
- Antivirals do prevent recurrent EM in patients with >6 outbreaks/year
- topical glucocorticoids (for skin) and glucocorticoid gels (for mucosal involvement) are key for symptomatic relief
- people with debilitating recurrent EM sometimes need systemic immune suppression. This is rare.