By Gary M. White, MD
Persistent erythema multiforme (EM) is defined as a rash clinically and histologically consistent with classic erythema multiforme that is constantly present, unless suppressed with therapy. Recurrent EM, in contrast, comes and goes in discrete episodes, with normal skin (when off treatment) in between. In case reports, persistent EM has been associated with occult viral infections, particularly Epstein-Barr Virus (EBV), as well as inflammatory bowel disease and malignancy [Clin Exp Dermatol. 2014 Mar;39(2):154-7].
Typical EM targetoid lesions of the elbows, palms, groin and thighs are characteristic. Bulla may form. Bilateral conjunctival hyperemia and ulceration of the oral mucosa similar to that seen in Stevens-Johnson Syndrome may occur.
Prednisone, e.g., 1 mg/kg/day, may be used to rapidly control the initial eruption, but mycophenolate should be started for long-term control. Mycophenolate mofetil 1 g twice daily but not less (and given along with valaciclovir 1 gram BID), kept one patient clear without the need of prednisone [Arch Dermatol 2002;138:1547-1550]. Azathioprine and dapsone have also been used [J Eur Acad Dermatol Venereol 2001;15:54-8] as has thalidomide [Am J Clin Dermatol 2008;9:123-7].
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