Our patient showed some distinctive findings never reported previously in RIP: a histological focal keratinocyte necrosis, and the presence of autoantibodies reacting with a 110 kDa keratinocytic protein in immunoblot analysis. Because of a different prognosis, it is important to differentiate RIP and paraneoplastic pemphigus (PNP), although cases of ionizing radiation-induced PNP had also been described. As in our patient, RIP seems to respond well to systemic corticosteroids and immunosuppressive therapy, which induce remission within a few months.