BULLOUS PEMPHIGOID AND EPIDERMOLYSIS-BULLOSA ACQUISITA - DIFFERENTIATION BY FLUORESCENCE OVERLAY ANTIGEN MAPPING

Background and Design: From previous studies, we concluded that the fl uorescence overlay antigen mapping (FOAM) technique could be of value to the differential diagnosis of the acquired subepidermal bullous ski n disorders, bullous pemphigoid (BP) and epidermolysis bullosa acquisi ta (EBA). In these diseases, ultrastructural identification of the sit e of skin-bound IgG deposits at the epidermal basement membrane zone ( EBMZ) may be essential to the correct diagnosis. Since ultrastructural studies are more expensive, time-consuming, and less widely available than immunofluorescence, we addressed the question of whether the FOA M technique can reliably identify the site of IgG deposits at the EBMZ , and distinguish BP from EBA. For this purpose, the technique was app lied to perilesional skin from seven patients with BP and six with EBA , using computer-aided imaging of red-stained type VII collagen and gr een-stained IgG, according to previous findings. Results: Digitized mu lticolor FOAM images of perilesional skin from patients with BP showed nonoverlap band patterns of green-stained lamina lucida IgG deposits (ultrastructurally proven) and red-stained type VII collagen. By contr ast, FOAM images of EBA skin typically showed overlap patterns of gree n-stained sublamina densa IgG deposits and red-stained type VII collag en. These findings were observed also in skin tissue stored in Michel' s transport medium or stored frozen for 15 years. Conclusions: The com puter-aided FOAM technique may have great potential in distinguishing between IgG deposits above (BP) and just below (EBA) the lamina densa of the EBMZ in skin tissue. The technique is not as simple as saline-s plit skin methodology but offers more flexibility, and it certainly is quicker and less expensive than electron microscopy. Furthermore, the use of digitized fluorescence images offers improved possibilities fo r evaluating the various ''linear'' patterns of immune reactant deposi tion at the EBMZ in subepidermal bullous autoimmune skin diseases.