Repeat direct immunofluorescence (DIF) test, using 1 M NaCl treated skin, in the subepidermal autoimmune bullous diseases that contain IgG at the dermal epidermal junction

Knowledge of autoimmune bullous diseases has greatly increased with the recognition of new entities, and the use of the direct immunofluorescence (DIF) using 1 molar per liter of sodium chloride (1 M NaCl) treated skin has been proposed. To estimate the frequency with which the different DIF patterns are present, we performed a systematic study of the skin or oral mucosa samples in which linear deposits of IgG at the basement membrane zone were detected by routine DIF in the last 6 years. The DIF tests were done on 56 samples before and after splitting the epidermis from the dermis with 1M NaCl. In 40 biopsies (72%) IgG was found on either the epidermal side or on both sides after 1M NaCl split. These cases corresponded to bullous pemphigoid (n=33), herpes gestationis (n=5) and cicatricial pemphigoid (n=2). In 6 cases (10.7%), IgG deposits were observed only on the floor, five corresponding to bullous pemphigoid and one to bullous pemphigoid-like eruption induced by amoxicillin. Repeat direct immunofluorescence using 1M NaCl split skin indicates that at least 12% of patients who were initially diagnosed as bullous pemphigoid, may in fact suffer a different entity, requiring other techniques to achieve the right diagnosis. This test can be a useful routine screening for autoimmune bullous diseases.