Differentiation of bullous pemphigoid from epidermolysis bullosa acquisita on frozen skin biopsies.

Patients with bullous pemphigoid and epidermolysis bullosa acquisita may have similar clinical, histologic, and routine immunohistologic features. These two diseases can be distinguished by routine diagnostic studies either on a patient's serum tested by indirect immunofluorescence on salt-split normal skin or by obtaining a fresh perilesional skin biopsy, inducing a split at the lamina lucida, and testing for the site of IgG deposition by direct immunofluorescence. Often the serum studies are negative, while direct immunofluorescent studies yield the characteristic linear IgG staining of the basement membrane zone. To eliminate the need for a repeat biopsy to make a laboratory differential diagnosis, we studied the efficacy of salt-splitting perilesional skin biopsies that had been previously submitted and frozen for routine direct immunofluorescent studies. The biopsies were thawed, salt-split, and processed for direct immunofluorescence. Three epidermolysis bullosa acquisita biopsies and seven bullous pemphigoid biopsies examined demonstrated IgG staining at sites consistent with their respective diagnoses. The IgG appeared in the dermal side of the split biopsies in epidermolysis bullosa acquisita and predominantly, or exclusively, in the epidermal side in bullous pemphigoid. Thus the direct immunofluorescent study of previously frozen and subsequently salt-split skin biopsies may be used for the differential diagnosis of bullous pemphigoid from epidermolysis bullosa acquisita. In most cases, it may eliminate the need for a repeat biopsy.