[A case of microscopic polyangiitis with silicosis].

A 76-year-old man was admitted to our hospital because of increasing size of lung nodules, while he was under observation for silicosis at another hospital. As the result of bronchoscopic biopsy, it was confirmed that they were silicotic nodules. However, he was hospitalized again about one month later due to left spontaneous pneumothorax. The pneumothorax improved immediately by persistent drainage of the thoracic cavity, but he developed a fever on day 9, and ground-glass opacities in both lungs also became exacerbated in spite of our administration of antibiotics. In addition, the level of MPO-ANCA increased markedly and multiple 3-10mm sized purpurae was seen on the right thigh on day 29. Skin biopsy specimens revealed infiltration of histiocytes and lymphocytes around medium-sized vessels in lower dermis. We diagnosed microscopic polyangiitis, then treated with steroid and immunosuppressive therapy. Fever and radiological findings improved significantly from the day after initiation of steroid administration. The patient was discharged on day 92 because of the improvement of his respiratory condition. We report a case of microscopic polyangiitis with silicosis, which markedly improved by steroid and immunosuppressive therapy.