**Abstract**

Autoimmune bullous diseases are a group of rare, chronic blistering diseases that affects the skin and mucous membranes. Mucous membrane pemphigoid (MMP) is the most frequently occurring autoimmune bullous disease in the oral cavity, followed by pemphigus vulgaris (PV). Early diagnosis of MMP or PV is critical for proper management and prevention of potential serious complications. This study was based on a retrospective review of 39 cases that were classified as MMP (25 patients) or PV (14 patients). Nikolsky's sign characterized by epithelial detachment as a result of slight pressure or rubbing the oral mucosa is a simple test that can confirm the existence of gingival desquamation. A positive reaction was confirmed in 38 patients (97.4%) at their first visit. This result indicates that patients showing positive Nikolsky's sign should include MMP or PV in the differential diagnosis and, in that case, histopathological examination and direct immunofluorescence testing are critical to establish the final diagnosis. For the early diagnosis of autoimmune bullous disorders, oral healthcare providers should consider the use of the test for Nikolsky's sign that may ultimately lead to the early diagnosis of MMP and PV or other diseases or disorders.

**Keywords:** gingival diseases, pemphigoid benign mucous membrane, pemphigus, oral medicine, autoimmune diseases
