An unusual case of Sweet syndrome in a child: overlapping presentation with erythema elevatum diutinum.

In 1964, Sweet described an acute febrile neutrophilic dermatosis. It is now widely accepted that Sweet syndrome is one of the associated neutrophilic dermatoses. Herein, we describe an unusual case of Sweet syndrome in a 5-year-old child who suffered from recurrent papules, plaques, and blisters on his face and trunk after the initial onset of fever without an obvious cause. Two skin biopsies were performed. The histopathological findings of the left arm biopsy showed a subepidermal blister with dense infiltrating neutrophils within the blister that were superficial to the middle layer of the dermis. The biopsy from a plaque on the left leg showed a dense infiltrate of neutrophils and a large number of infiltrating histiocytes superficial to the middle layer of the dermis. Direct immunofluorescence of a skin biopsy from the left arm confirmed that immunoglobulin M (IgM), IgG, IgA, and C3 expression were negative.