Erythema multiforme in children

Differential diagnosis

Urticaria is a frequent finding in children, and at times it is hard to differentiate from EM, especially early after presentation. History can help differentiate between these distinct conditions; EM involves fixed lesions for a few days, while urticaria (from allergic reaction or infection) will likely be transient (appear and disappear repeatedly) and will be self-limiting within a few days. However, at times the conditions are indistinguishable, and this has been coined urticaria multiforme.⁴

The most important differential diagnoses for EM that involve the mucous membranes are Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis. All 3 are immune-mediated epidermal conditions with variable clinical presentations; however, SJS and toxic epidermal necrolysis each have high mortality and lack an effective treatment.⁵ While in the past these conditions were considered to be on a continuum, they are now recognized as having distinct features and diverse outcomes, resulting in the need for different management strategies. Erythema multiforme is mostly considered to be papular and generally has target-like lesions; SJS usually contains widespread erythematous or purpuric macules with blisters.⁶

Treatment

For children who present with EM, treatment is generally supportive, with observation. Some will benefit from topical steroids or antihistamines.⁷ The use of systemic steroids among children has been a source of debate.⁸ Since EM is a self-limiting condition in most children, systemic steroids should be reserved for the most severe cases—serving as an adjuvant therapy; aiming to suppress cytokine and chemokine response, as well as T cell function; and decreasing adhesion of inflammatory molecules to blood vessel endothelium.⁹

For children who present with signs of herpes infection, early after its onset primary care physicians should consider antiviral treatment (acyclovir), as it seems to reduce the severity and duration of EM eruptions in some children. One retrospective case series suggested that herpes-associated EM can be precipitated by sun exposure and may not respond to treatment with oral or topical acyclovir.¹⁰ Prophylactic treatment with acyclovir can be considered, but evidence is limited.

When oral mucous membranes are involved or when children are systemically unwell, in pain, or experiencing considerable discomfort, admission to hospital for hydration should be considered.