Pseudosclerodermatous panniculitis after irradiation and bronchiolitis obliterans organizing pneumonia: simultaneous onset suggesting a common origin.

Due to the technical evolution of radiation therapy of breast carcinoma, new manifestations occur as side effects. Newly described unexpected cutaneous events are morphea of the breast and pseudosclerodermatous panniculitis after irradiation (PPAI). They appear as specific consequences of megavoltage radiation. Radiotherapy-induced bronchiolitis obliterans organizing pneumonia (R-BOOP) is one of the pulmonary manifestations due to recent advances in radiotherapy of breast carcinoma. We report a case of PPAI and R-BOOP of simultaneous onset in a 60-year-old woman 6 months after megavoltage radiation therapy for breast carcinoma. We also noted an improvement of both unexpected reactions with systemic corticosteroid therapy and a common relapse when tapering the treatment. Only eight cases of PPAI have previously been reported. We believe that this entity is often underdiagnosed. The symmetrical onset and parallel evolution suggest a common origin for PPAI and BOOP in our case: the megavoltage radiation therapy. The pathogeny of R-BOOP is not direct toxicity of irradiation because untreated areas can also be affected. Pathogenesis of PPAI remains unknown, but a simultaneous onset with R-BOOP suggests a similar mechanism. While a cumulative dose of irradiation does not seem to be determinant an immune reaction to neoantigens induced by radiation could be an hypothesis.