Histology of linear IgA disease, dermatitis herpetiformis, and bullous pemphigoid.

The histologic appearances of cutaneous biopsy specimens from 30 patients with linear IgA disease with a continuous band of IgA along the basement membrane, four patients with a linear pattern of granular IgA along the basement membrane, 26 patients with dermatitis herpetiformis who had IgA in the papillary dermis, and 23 patients with bullous pemphigoid who had IgG and/or C3 along the basement membrane were compared. Those with linear and granular IgA and dermatitis herpetiformis differed from those with bullous pemphigoid in five respects. Multiple microabscesses and fibrin at tips of papillae and leukocytoclasis were less common in bullous pemphigoid, whereas a dense infiltrate of eosinophils in and below bullae and a linear infiltrate of eosinophils along the basement membrane were more common in bullous pemphigoid. Also, multilocular bullae and acantholysis were more common in dermatitis herpetiformis than in bullous pemphigoid. Linear IgA disease differed from dermatitis herpetiformis in two respects. Acantholysis and fibrin at the tips of papillae and leukocytoclasis were more common in dermatitis herpetiformis. The specimens from patients with granular IgA did not differ significantly from those with linear IgA or dermatitis herpetiformis. The appearances of biopsy specimens of patch tests with potassium iodide taken from 11 patients with dermatitis herpetiformis and linear or granular IgA disease were similar to those taken from spontaneous lesions.