DSG1 and Feingold syndrome: Like the nonendemic forms of PF seen in the USA and worldwide, FS is characterized by subcorneal blisters with acantholysis and pathogenic IgG4 autoantibodies that recognize conformational and calcium-dependent epitopes on the ectodomain of desmoglein 1 (Dsg1), a key desmosomal adhesion molecule in the epidermis (15, 17–24).