[Five cases of pneumonitis induced by sho-saiko-to]

We report five cases of pneumonitis induced by sho-saiko-to. The patients complained of coughing (4/5), dyspnea (4/5), and pyrexia (3/5). The duration of sho-saiko-to treatment ranged from 4 to 1155 days. Abnormal laboratory findings included high levels of C-reactive protein (4/5), leucocytosis (4/5), severe hypoxemia (4/5), low vital capacity (3/5), and low diffusing capacity (5/5). Chest X-ray and CT films revealed diffuse reticulonodular or ground-glass shadows in both lung fields (4/5). Bronchoalveolar lavage was done in three cases, and revealed lymphocytosis in two cases and abnormally low CD4/8 ratios in three cases. The results of lymphocyte stimulation tests against sho-saiko-to and its component were positive in 3 of 5 cases. After discontinuation of sho-saiko-to, corticosteroids were given in all cases. Symptoms were relieved, and laboratory data and chest X-ray findings returned forward normal. Sho-saiko-to toxicity should be included in the differential diagnosis of pneumonitis. If drug-induced pneumonitis is suspected, administration of sho-saiko-to should be stopped and corticosteroid therapy should be given immediately.