Abstract: Regional variation of bullous pemphigoid (BP) antigen and epidermolysis bullosa acquisita (ERA) antigen in normal human skin and differential diagnosis of subepidermal bullous diseases were respectively studied by indirect immunofluorescence and salt-spilt skin direct immunofluorescence (DIF).Higher expression of BP antigen was observed in popliteal fossa, antecubital fossa, upper back, lower back,medial side of thigh and lower abdomen.Higher expression of EBA antigen was observed in knee, popliteal fossa,dorsum of foot,antecubital fossa,elbow and lower abdomen.16 (64%) of 25 patients with subepidermal bullous diseases had basement membrane zone deposits of C3 or IgG and IgA by skin DIF.However,salt-split skin DIF showed that all (100%)of 25 patients had IgG or with C₃ and IgA deposits on the epidermal or dermal side of salt-split skin.These rusults suggest that high expression of CP antigen in different regions of normal human skin correlates with the sites of predilection of BP lesions, but the expression of EBA antigen correlates partially with the sites of predilection of EBA lesions.Salt-split skin DIF can increase DIF positive rate and be used for the differential diagnosis of subepidermal bullous diseases depending on the sites of immunoglubin and complement deposited in salt-split skin.

Key words: Skin dieases, bullous, Antigens, Diagnosis, differential