A case of clinically amyopathic dermatomyositis that was refractory to intensive immunosuppressive therapy including tofacitinib, but successfully treated with plasma exchange therapy.

Clinically amyopathic dermatomyositis (CADM) patients often develop rapidly progressive interstitial lung disease (RP-ILD). A high level of anti-melanoma differentiation-associated gene 5 antibodies (anti-MDA5 Ab) before treatment is associated with RP-ILD development, a poor treatment response, and poor survival. The prognosis of CADM patients remains poor due to ILD even with combined intensive immunosuppressive therapy. Recently, several additional therapies, including tofacitinib (TOF) and plasma exchange (PE) therapy, have been reported to be effective. We herein report a case of CADM-ILD with a high level of anti-MDA5 Ab that was refractory to combined intensive immunosuppressive therapy including TOF, but successfully treated with PE. The following are possible reasons why TOF was ineffective: (1) cytokines that were not suppressed by TOF played an important role in RP-ILD; (2) TOF was administered later than previously reported; and (3) TOF did not suppress pathological substances such as antibodies. On the other hand, PE removes cytokines and various pathological substances. Therefore, PE may be a more reasonable additional therapy for intractable CADM-ILD.