Early Initiation of Plasma Exchange Therapy for a Patient with Anti-MDA5 Autoantibody Positive Dermatomyositis Developing Rapidly Progressive Interstitial Lung Disease.

Dermatomyositis (DM) is an categorized as one of idiopathic inflammatory myopathy (IIM) indicated by symmetrical proximal muscle weakness as well as characteristic cutaneous manifestations typical of DM. Clinically amyopathic dermatomyositis (CADM), a subtype of DM, shows only the skin involvement without any clinical signs of myositis. This condition is often associated with fatal anti-MDA5 antibody-positive rapidly progressive interstitial lung disease (RP-ILD), especially in Eastern Asian populations. Here, we report a CADM patient with anti-MDA5 antibody-positive RP-ILD whom we successfully treated by early initiation of plasma exchange (PE) together with multiple immunosuppressive therapies. In this patient, initial treatment with high-dose prednisolone, tacrolimus and intermittent intravenous cyclophosphamide had resulted in no obvious improvement in the respiratory condition. Therefore, soon after the first evaluation, we initiated plasma exchange therapy in addition to these multiple immunosuppressive therapies. Although the patient had pneumomediastinum, cytomegalovirus and fungal infections over the clinical course, RP-ILD did gradually improved and the anti-MDA5 titer decreased down to within the normal range paralleled by improvement in the patient's respiratory condition.