The tissue for evaluation is obtained by the 4 mm punch biopsy. Fast freezing of the tissue is extremely important. In most cases the combination of different immunoglobulines and complement factors together with results of classic transmitted light histologic evaluation enables specific diagnosis. The site of biopsy is very important. In bullous or vesicular diseases its is the border of a vesicle, in lupus erythematodes and porphyria the sun exposed areas where the changes are suitable for diagnosis.
Examination done to early can be negative.
Biopsy should always follow detailed clinical and laboratory examination. ICS antibodies are not found in Hailey-Hailey disease. Bullous pemphigoid, BP IgG and c3 positivy in the area of basement membrane of the epidermis and adnexa and partially in the roof of the bulla. Morphologically similar epidermolysis bullosa acquisita shows autoantibody positivity rather in the bottom of the vesicle. In drug induced pemphigoids is IgG and c3 often positive in the basal layer of the epidermis.