Histiocytic erythema multiforme.

Erythema multiforme is histologically characterized by liquefactive degeneration along the dermal-epidermal junction, necrotic keratinocytes and a lymphocytic infiltrate. We report a 10-year-old boy with recurrent erythema multiforme major of undetermined etiology with unusual histologic findings. A skin biopsy taken at day 2 of his eruption revealed histologic features otherwise characteristic of erythema multiforme, but mediated instead by a CD68-positive infiltrate, resembling cutaneous Kikuchi's disease. To the best of our knowledge this is the first reported case of 'histiocytic' erythema multiforme.