Zero of five non-lesional domestic shorthair cats exhibited epidermal immunolabeling for S100A8/S100A9 (calprotectin) while ten of ten cats (5 domestic shorthair cats and 5 Persian cats) with dermatophytosis exhibited moderate to strong, multifocal to diffuse epidermal immunolabeling (Fig 5). The gene discussed is S100A9; the disease is dermatophytosis.