Pulse intravenous cyclophosphamide treatment for steroid-resistant interstitial pneumonitis associated with polymyositis.

Interstitial pneumonitis (IP) is a serious complication in polymyositis/dermatomyositis (PM/DM), leading to significant morbidity or mortality. Here, we report the successful treatment by pulse intravenous administration of cyclophosphamide in the early course of lung involvement in PM, and with subsequent low-dosage oral administration of azathioprine in a patient with steroid-resistant IP associated with PM/DM. Although the precise pharmacological mechanism induced by cyclophosphamide in this disease remains unclear, such a cytotoxic drug raises the possibility of control of steroid-resistant PM/DM-associated IP when used in the early course of IP.