How Sick Is This Toddler With a Rash?

Laurie Gordon, MD, MA


November 16, 2015

Erythema Multiforme

This clinical scenario is typical of a child presenting with erythema multiforme (EM) minor. EM is an acute, self-limited hypersensitivity reaction. About 90% of cases are believed to be triggered by infection (viral, bacterial, or fungal), most commonly herpes simplex. A much smaller percentage of cases are caused by a drug hypersensitivity; an exposure, such as poison ivy; or a systemic disease.[1] In some cases, a trigger cannot be identified. Herpes has been associated with recurrent EM.

EM typically presents with symmetrical macules or papules initially on extremities that evolve into target lesions. Atypical target lesions can also be seen; these lesions are raised, but may not have the classical targetoid center.[1] Mucosal involvement is minimal with EM minor, but may be more significant with EM major. There is limited epidermal detachment.

EM is classified as[2]:

  • EM minor: typical targets or raised, edematous papules distributed acrally; minimal mucosal involvement, or

  • EM major: typical targets or raised, edematous papules distributed acrally with more extensive mucosal involvement; epidermal detachment involves less than 10% of total body surface area.

The typical clinical course and characteristic features of EM include:

  1. The disease first manifests as macules and papules on the hands and feet, involving the palms and soles.

  2. The macules and papules develop a central dusky area that may be vesicular, which flattens and evolves leaving a central dark area, middle ring, and peripheral red/dusky border—forming the typical concentric "target" lesion (Figure 2).[3]

  3. Target lesions are most often most apparent peripherally.

  4. Lesions are often symmetrical.

  5. There are minimal systemic symptoms.

  6. Mucosal lesions usually involve the mouth.

  7. There is minimal epidermal detachment (<10%) and no risk of evolving into toxic epidermal necrolysis (TEN).

Distinguishing EM minor and major from their life-threatening cousins SJS and TEN is critical. SJS and TEN are believed to be caused by a different mechanism from that of EM. SJS and TEN can be distinguished by:

  • Characteristics of the rash (more blistering and often painful);

  • Distribution (more central rather than peripheral, and asymmetrical rather than symmetrical);

  • Extensive mucosal involvement;

  • Extensive epidermal detachment; and

  • Etiology (more likely to be drug-induced rather than infectious).

Figure 2. Target lesions.

Children with Rocky Mountain spotted fever, unlike the child described in this case, present with significant systemic symptoms. Vasculitis also is accompanied by systemic symptoms.

Other conditions that should be considered in the differential diagnosis are:

  • Kawasaki disease

  • Systemic lupus

  • Other vasculitis

  • Drug eruptions

  • Urticaria

  • Henoch-Schönlein purpura

  • Lyme disease

  • Other viral exanthems

  • Disseminated bacterial or fungal infection

  • Insect bites

  • Scabies

  • Leukemia or lymphoma

  • Secondary syphilis

Management is typically supportive because EM is usually self-limited, with lesions resolving within approximately 1 month. Systemic antihistamines are helpful for management of pruritus.

Recurrent EM has been linked to herpes; acyclovir may be a useful therapy in these patients.

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