Corticosteroid resistant interstitial pneumonitis in dermatomyositis/polymyositis: Prediction and treatment with cyclosporine

Objective. To determine the characteristics of corticosteroid resistant int erstitial pneumonitis (IP) in dermatomyositis (DM) and polymyositis (PM), a nd to evaluate the effect of cyclosporine on corticosteroid resistant TP in DM/PM. Methods. We analyzed retrospectively the incidence, clinical features, and corticosteroid responses of IP in 111 patients with DM (56) or PM (55). All patients with DM/PM were treated with prednisolone, and corticosteroid res istant IP was defined as a progression of IP despite administration of 1 mg /kg/day prednisolone for more than 4 weeks. We also evaluated the effect of cyclosporine on corticosteroid resistant IP in patients with DM/PM. Results. IP occurred in 24 of 56 DM and 12 of 55 PM patients. We then class ified IP in DM/PM according to serum CPK levels at the onset of IF; IP asso ciated with high CPK levels (type I) (19) and IP associated with normal CPK levels (type II) (17). Only 2 of 19 (11%) type I IP were resistant to pred nisolone therapy, while 14 of 17 (82%) type II IP were resistant to prednis olone therapy. Thus, patients with type II TP showed poorer prognosis than those with type I IP (one year survival rate: type I 89% vs type II 31%). C yclosporine was effective in all 5 cases with corticosteroid resistant IP i n DM/PM (one year survival rate 80%). Conclusion. (1) Corticosteroid resistant IP develops mostly in patients wit h DM/PM without CPK elevation at the onset of IP (type II IP), and (2) cycl osporine is effective for the corticosteroid resistant IP in DM/PM and sign ificantly prolongs survival of patients.