Radiotherapy-induced pemphigus vulgaris with autoantibodies targeting a 110 kDa epidermal antigen.

Background: Pemphigus is an autoimmune intraepidermal blistering disease mediated by autoantibodies targeting desmosomes. It can be induced by many triggers, such as ionizing radiation.

Methods: We report a case of radiotherapy-induced pemphigus (RIP) with a review of the published cases in the English and French literature.

Results: A 61-year old man was diagnosed to have epidermoid carcinoma of the piriform sinus and then received a 70 Gy radiation therapy. One month after the treatment completion, multiple blisters and erosions occurred initially on the site of irradiation, then in other skin areas. Histological examination showed an intraepidermal blister with acantholysis and necrosis of individual keratinocytes. Direct immunofluorescence and indirect immunofluorescence were typical of pemphigus. Immunoblot revealed antibodies reacting with a 110 kDa antigen. This feature was consistent with the diagnosis of RIP. Less than 20 cases of RIP have been reported previously. Mean age at diagnosis was 64.2 years, and there is a slight female preponderance. RIP occurred, in most cases, initially within the area of irradiation.

Conclusion: 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.