Acrosyringeal concentration of necrotic keratinocytes in erythema multiforme: a clue to drug etiology

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Abstract
Erythema multiforme (EM) is caused by various insults, frequently an infectious agent or a drug. It is current practice that histologic identification of the precipitating factor is not possible. We have observed a pattern of acrosyringeal concentration of keratinocyte necrosis in certain cases of EM and retrospectively studied 29 consecutive cases of EM to establish clinico-pathologic correlation for this finding. Acrosyringeal concentration was observed in 10 of 29 specimens, all 10 clinically drug related (Group 1). Nineteen specimens lacked this pattern (Group 2) of which 3 cases were clinically drug related (sensitivity= 0.8, specificity= 1.0). Eosinophils were present in the dermal infiltrate of 6 specimens from Group 1 and 2 specimens from Group 2 (p=0.025). Acrosyringeal concentration of keratinocyte necrosis in EM occurs in drug-related cases and is more likely to be accompanied by a dermal inflammatory infiltrate containing eosinophils. Drug concentration in sweat may explain this pattern with subsequent toxic and immunologic mechanisms leading to the fully evolved lesion.