Treatment of immune-mediated necrotizing myopathy (IMNM) in adults

anti-HMGCR: anti-3-hydroxy-3-methylglutaryl coenzyme A reductase; anti-SRP: anti-signal-recognition particle; IMNM: immune-mediated necrotizing myopathy; IV: intravenous; IVIG: intravenous immune globulin.

* Severe disease is distinguished from nonsevere disease by the presence of severe or rapidly progressive weakness resulting in difficulty walking, muscle atrophy, dysphagia, respiratory failure, and/or other severe organ damage.

¶ Glucocorticoid-sparing therapy may be started at the same time as or within 1 month of initiation of glucocorticoids, depending on disease severity.

Δ Azathioprine or mycophenolate may be substituted for methotrexate if contraindicated or not tolerated.

◊ IVIG could be considered as monotherapy in patients with contraindications to glucocorticoids.

§ Depending on clinical response, oral, weekly methotrexate may be tapered slowly (eg, down by 2.5 mg per month).

¥ Rituximab may be discontinued if deemed to be ineffective.

‡ IVIG monotherapy in the absence of glucocorticoids may be effective in some patients.

† Alternative for patients who fail to respond to this approach include azathioprine, mycophenolate mofetil, tacrolimus, and plasmapheresis.