IgA pemphigus and Sneddon Wilkinson disease: a spectrum of diseases?

Subcorneal pustular dermatosis (SPD), also known as Sneddon-Wilkinson disease, is a rare, benign, chronic disease characterized by sterile pustular eruption, typically involving the flexural sites of the trunk and proximal extremities. SPD is clinically and histopatologically identical to SPD-type IgA pemphigus. For differential diagnosis, immunologic evaluation is crucial. Here is presented an interesting case of differential diagnosis, in particular between SPD and SPD-type IgA pemphigus. Alternatively, SPD and SPD-type IgA pemphigus may be two extremes of a spectrum, with the same clinical and histologic presentation and a typical response to dapsone but with a different concentration of immunoglobulin at IFD and IFI, ranging from SPD (no IgA) to SPD-type IgA pemphigus (typical presence of IgA).