This 70 year old man presented with pruritic grouped vesicles on his extensor surfaces. This is a characteristic presentation with great pathology. The histology in this case is classic, with aggregates of neutrophils in the dermal papillae. The immunofluoresence was performed and confirmed the presence of IgA deposition in these papillae, but the diagnosis could be made on H&E. The differential diagnosis includes linear IgA disease, but the prominent dermal papillary aggegates would be unusual for that entity.
There is a moderate inflammatory infiltrate, involving the dermal papillae and extending to the mid-reticular dermis. At one edge of the biopsy, there is a subepidermal cleft.