DIF and IIF evaluates in vivo bound and circulating autoantibodies and are the preferred methods for diagnosing AIBDs. In pemphigus diseases and dermatitis herpetiformis, the titer of circulating autoantibodies reflects the disease activity. In patients with a classical clinical picture, the DIF confirms the diagnosis. Furthermore, this technique is essential in subtypes of AIBDs with atypical clinical manifestations (eg, no blisters or erosions) or clinically similar presenting manifestations, such as bullous pemphigoid, MMP, or EBA. A direct or indirect SSST is often crucial for the differential diagnosis between subtypes of these diseases, leading to proper treatment for severely affected patients.