[Clinical and pathological studies of organizing pneumonia]

Clinical and pathological studies on organizing pneumonia (OP) were performed in 16 cases diagnosed by transbronchial lung biopsy (TBLB). All patients were elderly and poorly-nourished with underlying disease, and suffered from fever and various respiratory symptoms. Results of laboratory studies in these cases were positive for C-reactive protein, negative for tuberculin reaction and showed high complement levels. Pathological findings demonstrated that there were two kinds of organizing process classified according to whether fibrin exudation was detected in Masson bodies or not. Twelve of the 16 cases were treated with prednisolone, and two cases were observed without administration. In nine of the 16 cases, abnormal shadows in chest X-ray disappeared, although abnormal shadows remained in five. Regarding the relationship between pathological findings and shadows in chest X-ray, Masson bodies without fibrin were observed in nine cases in which abnormal shadows in chest X-ray disappeared, but Masson bodies containing fibrin were observed in five cases in which abnormal shadows remained. These results suggest that there are two kinds of organizing process in OP. Steroid therapy tends to be ineffective in OP demonstrating organization containing fibrin caused probably by infection. However, prednisolone is effective in the OP associated with a fibrosing process, similar to idiopathic BOOP, without or with unrelated fibrin exudation of unknown origin.