Therapeutic plasmapheresis as an effective treatment for refractory anti-3-hydroxy-3-methylglutaryl coenzyme A reductase-positive immune-mediated necrotising myopathy.

Immune-mediated necrotising myopathy (IMNM) can be associated with autoantibodies to 3-hydroxy-3-methylglutaryl coenzyme A reductase (anti-HMGCR). We present a case of a man in his 60s with a 13-year history of relapsing anti-HMGCR-positive IMNM, intermittently partially responsive to various treatments including corticosteroids, methotrexate, mycophenolate, intravenous immunoglobulin, abatacept and rituximab. After a repeat presentation with severe weakness, plasmapheresis was commenced, resulting in rapid and significant improvement in muscle strength and biochemical markers, which was sustained for several months. A subsequent disease relapse following discontinuation of regular plasmapheresis responded successfully to a second treatment course of plasmapheresis. The case highlights the potential of plasmapheresis in managing refractory IMNM.