A 29-year-old healthy man visited our office because of a slight pain of the left lower limb. Physical examination revealed a tiny erythema, which did not reach a definitive diagnosis. A punch biopsy was performed at his urging. Histopathological examination showed a crust formation on the surface of the skin and a brightly eosinophilic substance in the dermis (Fig. 1). Other histological findings include a marked perivascular infiltrate of lymphocytes, eosinophils and plasma cells in the dermis (Figs. 2, 3) and extravasations in the upper dermis (Fig. 4).