Linear IgA bullous dermatosis v dermatitis herpetiformis. Quantitative measurements of dermoepidermal alterations.

Linear IgA bullous dermatosis (LAD), also known as "atypical dermatitis herpetiformis," is a disorder that is distinct from classic dermatitis herpetiformis (DH). In eight patients with DH and six with LAD, quantitative assessment of a variety of histopathologic variables was made. The number of rete tips with neutrophils in basal vacuoles and the length of the epidermal basement membrane zone (BMZ) associated with these findings were greater in LAD than DH. The number of microabscesses of neutrophils in the dermal papillae and the length of epidermal BMZ associated with them were greater in DH than in LAD. By using the number of microabscesses and the number of rete tips with neutrophils in basal vacuoles in a probability model, we found by retrospective analysis that a correct diagnosis could be made for LAD in 75% of biopsy specimens with a probability of 97% and in all cases of DH with a probability of 92%. Using this model, we made no misdiagnoses. This is the first diagnostic probability model in dermatopathology that expresses a confidence level in diagnosis.