What would you use to treat polymyositis refractory to high dose steroids, methotrexate, mycophenolate, IVIG, and cyclophosphamide?

Refractory polymyositis might be a red flag for an alternate diagnosis, like IBM or genetic muscle disease, especially in the absence of a myositis specific antibody, like SRP or HMGCR (the most common antibodies in PM/immune-mediated necrotizing myopathies).

If IIM is confirmed, then a combination ...