This is an exhaustive list of drugs which may (rarely apart from steroids) cause clinically relevant myopathy/myositis. I would like to draw your attention to Colchicine, which we often use longterm for conditions as common as Gout to uncommon ones like Behçet's and some other vasculitides. Though overwhelmingly asymptomatic in those with normal renal function, I've been cautioned by my neurology colleagues not to order EMG for patients on Colchicine as it will turn out invariably abnormal. I wonder if this applies also to any of the other drugs on this very exhaustive list.
When even throwing the kitchen sink (and that includes steroids, MTX, Azathioprine, cyclophosphamide, IVIG, Rituximab) fails in refractory DM/PM (and it's really autoimmune myositis and not Inclusion Body Myositis), perhaps Ruxolitinib may work? But, in this case report, does it work directly on the immune response by inhibiting JAK 1/2, or indirectly through remitting Myelofibrosis?
How about our fave pan-JAK inhibitor: Tofacitinib? Are the JAK inhibitors turning out to be a JAcK of all trades?