Patients with bullous pemphigoid and those with epidermolysis bullosa acquisita often demonstrate virtually identical clinical, histologic, and immunopathologic features. Although some patients can be distinguished by their pattern of circulating IgG anti-basement membrane zone antibody binding to 1 mol/L sodium chloride-split human skin, approximately 20% and 50% of bullous pemphigoid and epidermolysis bullosa acquisita patients, respectively, do not possess such antibodies. Hence this study sought to determine whether these patients can be distinguished by mapping the distribution of basement membrane zone im-munoreactants in patient skin split in vitro by 1 mol/L sodium chloride. All sodium chloride-treated samples from patients with bullous pemphigoid (n = 8), epidermolysis bullosa acquisita (n = 4), or other bullous skin diseases (n = 6) contained a lamina lucida cleavage plane bounded by bullous pemphigoid antigen and laminin; moreover, treatment of patient samples was performed without loss of tissue substrate or in situ immunoreactants. Deposits of IgG were found on the epidermal side of sodium chloride-treated skin from 13 of 14 bullous pemphigoid samples; IgG deposits in bullous pemphigoid samples were exclusively epidermal in eight, epidermal and dermal in five, and solely dermal in one. In contrast, IgG was found exclusively on the dermal side of sodium chloride-treated samples from patients with epidermolysis bullosa acquisita. Although IgG mapping distinguished bullous pemphigoid and epidermolysis bullosa acquisita patients in 94% of these samples, the distribution of C3 in sodium chloride-treated patient skin was more variable and less predictive diagnosti-cally. This study also found that five patients in whom basement membrane zone IgG was undetected in untreated skin showed IgG in their sodium chloride-treated samples. Similarly, four bullous pemphigoid patients showed C3 or C4d on the surface of basal keratinocytes in sodium chloride-treated, but not untreated, skin.
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