Subepidermal Bullous Dermatoses

Abstract

The autoimmune bullous dermatoses discussed in this chapter are the consequence of defects at or near the basement membrane zone. At the light microscopy level, the subepidermal bullous dermatoses can generally be classified based upon the predominant type of inflammatory cells within the blister space: cell-poor, eosinophils, neutrophils, or lymphocytes. The pauci-inflammatory group includes epidermolysis bullosa (EB) and porphyria cutanea tarda. Using transmission electron microscopy, EB are further classified into four major types (EB simplex, junctional EB, dystrophic EB, and Kindler syndrome) according to the plane of the cleavage. Entities with predominance of eosinophils within the blister space include bullous pemphigoid, mucous membrane pemphigoid/cicatricial pemphigoid, and pemphigoid gestationis. Those containing mainly neutrophils are linear IgA disease, anti-laminin gamma-1 pemphigoid, epidermolysis bullosa acquisita, bullous lupus erythematosus, and dermatitis herpetiformis. Lymphocytes are prominent in lichen planus pemphigoid. Due to overlapping histologic features, direct immunofluorescence (DIF) studies are necessary to distinguish various entities. Of those with similar DIF findings, indirect immunofluorescence (IIF) studies performed on sodium chloride split skin are essential to determine the location of the antigens. In the setting of similar IIF findings as noted in EBA and anti-laminin gamma-1 pemphigoid, immunoblot is needed to confirm the diagnosis.