How is the diagnosis of Eosinophilic Fasciitis confirmed histologically?
By performing a full thickness, deep wedge biopsy of an involved area. The biopsy should be deep enough to acquire skin, subcutis, fascia, and muscle for the study. Although inflammation and fibrosis are generally found in all layers (except for the epidermis which is normal), they are usually most intense in the subcutis and fascia. The inflammatory infiltrate consists of abundant lymphocytes, plasma cells, and histiocytes. Eosinophilic infiltration can be seen, especially early in the disease process, but is variably present.