Evaluation of direct immunofluorescense on salt split skin in the differentiation of subepidermal autoimmune Bullous dermatoses

Background: Bullous pemphigoid (BP) is the prototype of subepidermal autoimmune bullous dermatoses (SABDs). Direct immunofluorescence on salt split skin substrate (DIF-SS) is one of the methods used to differentiate this group of dermatoses. Objective: We conducted this study in order to delineate the results of DIF-SS in SABD patients. Patients and Methods: Seventeen patients with a BP-like clinical picture referred to Razi Hospital in 1378, who had linear immunodeposits along basement membrane zone in direct immunofluorescence, were studied. Considering only histopathologic and clinical data, a final diagnosis was established for each patient. DIF-SS was performed on perilesional skin sample of patients. DIF-SS and histopathology results and the final diagnosis were recorded and compared for each patient. Results: In DIF-SS, eleven patients (65%) had combined (Epidermal and dermal), two patients (12%) had epidermal and four patients (23%) had dermal pattern. The final diagnoses were BP in ten patients and epidermolysis bullosa acquisita (EBA) in two others. We were unable to differentiate BP from EBA in two patients. In ten patients who were diagnosed finally as BP, nine patients (90%) had combined pattern and only one case (10%) showed epidermal staining in DIF-SS. Conclusion: Surprisingly, in contrast to the results of the previous studies on pemphigoid patients using either IIF-SS or DIF-SS in which the epidermal pattern had been reported to be much more common than the combined pattern, the combined pattern was nine times more frequent than the epidermal pattern in this study. Perhaps, the difference in target antigens in our patients may be the underlying reason for the difference in our results.