Plasma exchange in dermatomyositis/polymyositis: beneficial effects in three cases.

We describe ameliorative effects of plasmapheresis in three patients with dermatomyositis-polymyositis resistant to other therapy, particularly prednisolone. Serologically, the cases were marked, respectively, by a weakly-reactive speckled-type ANA; a strongly reactive speckled-type ANA and an unidentifiable precipitin line by CIEP; and an antibody to cytoplasm and to Jo1. The remission induced by plasmapheresis was temporary in one case and lasting, with low doses of prednisolone, in two. The nuclear autoantibody in case two became undemonstrable after plasmapheresis but recurred during a subsequent relapse. This experience with plasmapheresis in myositis supplements a substantial reported experience of benefit from this therapy.