Toxic Myopathies

Christopher T. Doughty, MD; Anthony A. Amato, MD, FAAN Muscle and Neuromuscular Junction Disorders p. 1712-1731 December 2019, Vol.25, No.6 doi: 10.1212/CON.0000000000000806
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PURPOSE OF REVIEW This article reviews the pathogenesis, clinical features, and management of toxic myopathy related to common medications, critical illness, and illicit substances.

RECENT FINDINGS Muscle symptoms are common among statin users and are usually reversible after discontinuation of the statin; rarely, however, statins trigger an immune-mediated necrotizing myopathy that persists and requires immunomodulatory therapy. Autoantibodies targeting 3-hydroxy-3-methylglutaryl coenzyme A reductase can distinguish the toxic and immune-mediated forms. Immune checkpoint inhibitors, increasingly used in the treatment of advanced cancer, have recently been associated with the development of inflammatory myositis. A reversible mitochondrial myopathy has long been associated with zidovudine, but recent reports elucidate the risk of myopathy with newer antivirals, such as telbivudine and raltegravir.

SUMMARY The medications most commonly associated with myopathy include statins, amiodarone, chloroquine, hydroxychloroquine, colchicine, certain antivirals, and corticosteroids, and myopathy can occur with chronic alcoholism. Certain clinical, electrodiagnostic, and histologic features can aid in early recognition. Stopping the use of the offending agent reverses symptoms in most cases, but specific and timely treatment may be required in cases related to agents that trigger immune-mediated muscle injury.

Address correspondence to Dr Christopher T. Doughty, Department of Neurology, Brigham and Women’s Hospital, 60 Fenwood Rd, Boston, MA 02115, ctdoughty@partners.org.

RELATIONSHIP DISCLOSURE: Dr Doughty has received personal compensation as a CME lecturer for Oakstone and has received research/grant support from the National Institutes of Health (NIH) for a clinical trials fellowship (U24NS107154). Dr Amato has received personal compensation as an associate editor for Neurology. Dr Amato has received research/grant support from Acceleron, NIH (U01AR070498-01A1 and U24NS107154-01), Orphazyme, and Pharnext and royalties for authorship of Neuromuscular Disorders and Harrison’s Textbook of Internal Medicine from McGraw-Hill Education.

UNLABELED USE OF PRODUCTS/INVESTIGATIONAL USE DISCLOSURE: Drs Doughty and Amato discuss the unlabeled/investigational use of immunotherapy for the treatment of drug-induced inflammatory myopathies.

© 2019 American Academy of Neurology.