Immune-mediated necrotising myopathy: a rare cause of hyperCKaemia

Abstract

Immune-mediated necrotising myopathy (IMNM) is a type of inflammatory myopathy characterised by acute or subacute severe proximal muscle weakness, significantly elevated creatine kinase levels, and prominent myofibre necrosis and regeneration with little or no inflammation. A subtype of IMNM identified by anti-HMG-CoA reductase (HMGCR)antibodies has been shown to be associated with statin exposure. Treatment of IMNM consists of immunosuppression with steroids, steroid-sparing agents, intravenous immune globulin and/or biologics. We present here a case of anti-HMCGR-associated IMNM and review the pathophysiology, diagnosis and treatment to increase physician awareness of this rare and debilitating condition.

Anti-HMGCR myopathy presenting with acute systolic heart failure

“…However, these findings were not stratified according to the specific NAM subtype 7. Multiple recent case reports of anti-HMGCR myopathy do not describe significant cardiac involvement 2–6. A recent case report does describe the rapid progression of heart failure in a patient with pre-existing idiopathic inflammatory myopathy, but does not further specify a specific diagnosis 16.…”

“…Anti-HMCGR myopathy is a form of NAM and is a rare side effect of statin use, which is estimated to occur in 2–3 out of every 100 000 statin users 1. Multiple recent case reports, including the aforementioned case, describe atorvastatin-induced NAM, although pravastatin, rosuvastatin and simvastatin have also been implicated 2–7 12. However, no studies have been done investigating the relative risk of developing NAM with different statins (such as hydrophobic vs hydrophilic statins), and the preponderance of atorvastatin-induced cases likely represents prescribing practices as opposed to a specific drug effect 13.…”

“…Necrotising autoimmune myopathy (NAM) is a rare but increasingly recognised side effect of statin use 1. Multiple recent case reports describe cases of anti-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) myopathy induced by statins, although none of them describes significant cardiac involvement 2–6. It is being increasingly shown that early recognition and treatment with immunosuppression improves outcomes in NAM 7.…”

<p>Immune-Mediated Necrotizing Myopathy Initially Presenting as Erythema Nodosum</p>

“…13,14 But the addition of an appropriate high-dose second-line agent (eg, methotrexate, azathioprine, and mycophenolate mofetil) is often required because prednisone monotherapy is rarely sufficient, especially for patients with anti-SRP myopathy. 5,6 Rituximab or IVIG could be used first line in anti-SRP-associated or anti-HMGCR-associated IMNM. 14 If initial treatments are ineffective, all patients should use rituximab and IVIG at 6 months to get better prognosis.…”

“…2 It may also involve muscles of the respiratory and cardiovascular systems, which can cause severe morbidity and mortality. 2,[5][6][7] The recognized risk factors for IMNM include drug exposure (statins, pembrolizumab, and nivolumab), 8 connective tissue diseases, cancer (commonly gastrointestinal adenocarcinomas, and lung cancer) 9,10 and rarely, human immunodeficiency virus infection. 4 The muscular histopathology of IMNM shows significant myofiber necrosis and minimal lymphocytic infiltrates without perifascicular atrophy.…”