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

OBJECTIVE

To determine the characteristics of corticosteroid resistant interstitial pneumonitis (IP) in dermatomyositis (DM) and polymyositis (PM), and to evaluate the effect of cyclosporine on corticosteroid resistant IP 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 resistant 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 classified IP in DM/PM according to serum CPK levels at the onset of IP; IP associated 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 prednisolone therapy, while 14 of 17 (82%) type II IP were resistant to prednisolone therapy. Thus, patients with type II IP showed poorer prognosis than those with type I IP (one year survival rate: type I 89% vs type II 31%). Cyclosporine was effective in all 5 cases with corticosteroid resistant IP in DM/PM (one year survival rate 80%).

CONCLUSION

(1) Corticosteroid resistant IP develops mostly in patients with DM/PM without CPK elevation at the onset of IP (type II IP), and (2) cyclosporine is effective for the corticosteroid resistant IP in DM/PM and significantly prolongs survival of patients.