COL17A1 and autoimmune bullous skin disease: Four of these 21 sera, 2 with MMP, 1 with anti-p200 pemphigoid, and 1 with linear IgA disease, were diagnosed as “pemphigoid” by the BIOCHIP technique based on detection of autoantibodies against BP180 and positive staining on esophagus and/or salt-split skin (Figure3).