A vesiculobullous disease is a type of mucocutaneous disease characterized by vesicles and bullae (i.e. blisters). Both vesicles and bullae are fluid-filled lesions, and they are distinguished by size (vesicles being less than 5–10 mm and bulla being larger than 5–10 mm, depending upon which definition is used). In the case of vesiculobullous diseases which are also immune disorders, the term immunobullous[1] is sometimes used.