ABSTRACT
Direct immunofluorescence of the uninvolved skin has become the most reliable test for establishing the diagnosis. It has been argued that the subepidermal blistering diseases may represent a spectrum of disease and not clearly defined entities. This overlap may occur in the clinical features, immunoglobulin class, site and pattern of immunoglobulin deposition and so-called target antigens. Although there are characteristic sites for the eruption in a number of the disorders, for example the extensor regions of elbows and knees and the buttocks in dermatitis herpetiformis, periumbilical region in pemphigoid gestationis and pubic region in childhood linear immunoglobulin A disease, difficulty in making a diagnosis will arise if the eruption is widespread, as may occur with any of them. Thus, although the subepidermal bullous disorders have been divided into a number of entities, there is considerable overlap in their clinical, immunological and etiological features and response to treatment.
