Statin-Associated Autoimmune Myopathy and Other Forms of Myositis

Abstract

The autoimmune myopathies are a heterogenous family of diseases characterized by weakness, elevated muscle enzymes, and abnormal muscle biopsies. Immune-mediated necrotizing myopathy (IMNM), dermatomyositis, the antisynthetase syndrome, and inclusion body myositis are the four main types of autoimmune myopathy. Statin-associated autoimmune myopathy is a subtype of IMNM that can occur as a rare side effect of statin treatment and is diagnosed based on the presence of autoantibodies recognizing HMG-CoA reductase, the pharmacologic target of statins. This chapter will focus on the clinical features, risk factors, management, and pathogenesis of the autoimmune myopathies, with an emphasis on statin-associated autoimmune myopathy. The autoimmune myopathies not associated with statins are also presented to help clinicians differentiate these myopathies from statin-associated autoimmune myopathy and to decide when statins may be used in these patients.