[A case of IgG4-related disease with deterioration in pulmonary and pituitary involvements during a 10-year clinical course of inflammatory pseudotumor].

A 71-year-old man underwent pleural biopsy due to left pleural effusion and pleural thickening in August, 2001. An inflammatory pseudotumor (IPT) was diagnosed, and therefore systemic oral steroid therapy (prednisolone [PSL] 30 mg/day) was initiated. However, after tapering PSL to 7.5 mg/day, a complication of secondary central diabetes insipidus due to hypophysitis developed in 2008. As his pulmonary condition deteriorated over time and he began to experience exertional dyspnea, he was admitted to our hospital for re-evaluation of the disease in October, 2010. High-resolution CT (HRCT) revealed pulmonary involvements distributed in the interstitium and a high serum IgG4 level (240 mg/dl). Upon re-evaluating the pleural biopsy specimens of the first visit, we found lymphoplasmacytic-type IPT with approximately 10% IgG4-positive plasma cells in the affected areas. After increasing the PSL dose up to 0.6 mg/kg/day, his serum IgG4 levels decreased, his dyspnea improved, and the radiological findings of his pulmonary and pituitary involvements improved. This case was diagnosed as lymphoplasmacytic type IPT which appeared to be highly homologous with IgG4-related disease due to high serum levels of IgG4, pituitary involvements and the observed efficacy of PSL.