Necrotizing autoimmune myopathy (NAM) is a relatively recently discovered subgroup of inflammatory myopathies. NAM is characterized by predominant muscle fiber necrosis and regeneration with little or no inflammation.1 One subgroup of NAM is 3-hydroxy-3-methylglutaryl-CoA reductase antibody (HMGCR Ab)-related immune-mediated necrotizing myopathy (IMNM), which occurs (rarely) after statin exposure, with a rough incidence of two per 1 million per year.2,3,4,5,6
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December 2017Approximately one in 10,000 people exposed to statins develop myalgia and myopathy, which reverse after doctors discontinue statins.7 These patients are usually in their fifth decade of life and present with subacute to chronic symmetric muscular weakness with high creatine phosphokinase (CPK) levels (9,718 ± 7,383 IU/L) and poor response to steroids.2 The presentation can occasionally be complicated by severe respiratory weakness, dysphagia and ventricular dysfunction.3
Below, we discuss two patients with HMGCR Ab-related IMNM with severe respiratory muscle weakness. Our case series highlights the uncommon presentation of respiratory muscle involvement leading to respiratory failure, and identifies the best treatment.
Case Report 1
The first patient was a 76-year-old Caucasian male who presented with progressive subacute proximal weakness in his upper and lower extremities, and difficulty in swallowing. His muscle weakness started 10 weeks prior to admission and gradually worsened. One week prior to his admission, he noticed difficulty swallowing and nasal regurgitation.