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immune-mediated necrotizing myopathy (IMNM)

Etiology: - autoantibody directed against HMG-CoA reductase, the pharmacologic target of statins [1,2] - occurs in a minority of patients with statin myopathy - continues to progress even after discontinuing statin [2] - may occur in the absence of statin prescription in patients consuming large quantities of plant sterols - case report involving Camargue red rice [4] Clinical manifestations: - severe, rapidly progressive proximal muscle weakness - few extramuscular manifestations [] Laboratory: - high serum creatine kinase - HMG CoA reductase Ab in serum - signal recognition particle Ab in serum/plasma Management: - immunosuppression - glucocorticoid administration - prednisone [1] - most cases refractory glucocorticoids alone [7] - recommended induction regimens - glucocorticoids + methotrexate, intravenous immune globulin (IVIG), rituximab, azathioprine, or mycophenolate - IVIG + rituximab in refractory cases [7] - PCSK9 inhibitors may be alternative for lowering LDL cholesterol [6]

General

autoimmune disease statin myopathy

References

  1. Mohassel P and Mammen AL The Spectrum of Statin Myopathy. Curr Opin Rheumatol. 2013;25(6):747-752. PMID: 24061077 http://www.medscape.com/viewarticle/814502
  2. Medical Knowledge Self Assessment Program (MKSAP) 16, 17, 18, 19. American College of Physicians, Philadelphia 2012, 2015, 2018, 2022
  3. Mohassel P, Mammen AL. Statin-associated autoimmune myopathy and anti-HMGCR autoantibodies. Muscle Nerve. 2013 Oct;48(4):477-83 PMID: 23519993
  4. Brooks M Diet May Be a Source of 'Statin' Exposure. Medscape - Mar 21, 2018. https://www.medscape.com/viewarticle/894299 - Barbacki A, Fallavollita SA, Karamchandani J, Hudson M. Immune-Mediated Necrotizing Myopathy and Dietary Sources of Statins. Ann Intern Med. 2018. Feb 20 PMID: 29459987 http://annals.org/aim/article-abstract/2673071/immune-mediated-necrotizing-myopathy-dietary-sources-statins
  5. Musset L, Allenbach Y, Benveniste O et al Anti-HMGCR antibodies as a biomarker for immune-mediated necrotizing myopathies: A history of statins and experience from a large international multi-center study. Autoimmun Rev. 2016 Oct;15(10):983-93. Review. PMID: 27491568
  6. Garcia-Diaz JD, Corral-Bueno TM, Mesa-Latorre JM et al Proprotein Convertase Subtilisin/Kexin Type 9 Antibody and Statin- Associated Autoimmune Myopathy. Ann Intern Med. 2019. Feb 19 https://annals.org/aim/article-abstract/2725149/proprotein-convertase-subtilisin-kexin-type-9-antibody-statin-associated-autoimmune
  7. Rothaus C. A Woman with Weakness, Dark Urine, and Dysphagia. NEJM Resident 360. July 17, 2019 https://resident360.nejm.org/clinical-pearls/a-woman-with-weakness-dark-urine-and-dysphagia