The histology and immunopathology of dermographism.

Twelve patients with dermographism were studied by histological examination. Six spontaneous lesion showed perivascular lymphocytosis. Biopsy of 6 induced lesions showed neutrophiles at 15-30 min and lymphocytes at 1 h or more. One patient biopsied both at 15 min and 2 h showed both microscopic pictures successively. Immunofluorescence of spontaneous or induced lesions in 5 patients was not significant. Studies of T cell subsets of an induced lesion at 30 min showed a moderate number of T helper cells. Mast cell and eosinophile changes were not important. These studies of dermographism imply successive changes with time in perivascular cellular pathology.