Serum IgG basement membrane zone antibodies showing combined epidermal-dermal staining on split skin substrate in bullous pemphigoid by IIF microscopy

Linear IgG antibody staining in a combined pattern, epidermal-dermal, on basement membrane zone-split skin substrate characteristic of bullous pemphigoid and, rarely, bullous lupus erythematosus. This pattern is also referred to as "staining the roof and floor of the blister."