Statin Induced Muscle Toxicity - Summary Clinical Presentation: • Elevations of serum creatine kinase with proximal myalgia and weakness without skin involvement Epidemiology • 10% to 15% of individuals on statin therapy experience Statin-Associated Muscle Symptoms (SAMS) • 1 of 100,000 patients taking a statin, IMNM Duration: • The onset of muscle symptoms: weeks to months after the initiation of statin therapy / may occur at any time during treatment Statin-Induced Myalgia/Myopathy Symptoms: • Proximal symmetric muscle weakness • Soreness • Myalgia • Myositis • Rhabdomyolysis • Difficulty raising the arms above the head, arising from a seated position, or climbing stairs • Fatigue or tiredness • Myoglobinuria DDX: • Inflammatory myopathy, rhabdomyolysis, toxic myopathy, hypothyroid-induced myopathy, Guillain-Barré syndrome (GBS), systemic lupus erythematosus (SLE), polymyositis, dermatomyositis, inclusion body myositis antisynthetase syndrome, immune-mediated necrotizing myopathy (IMNM), Lambert-Eaton myasthenic syndrome (LEMS), systemic sclerosis. Statins → Inflammatory myopathies such as • Statin-induced myopathy (SAMS) → Direct muscle injury • Immune-mediated necrotizing myopathy (IMNM) → Antibodies to hydroxymethylglutaryl (HMG)-CoA reductase (HMGCR) - Necrotizing myopathy: Inflammatory statin myopathy is characterized by a macrophagocytic infiltrate engulfing necrotic muscle fibers Risk of myopathy appears to be lowest with: • Fluvastatin • Pravastatin • Pitavastatin Risk of muscle injury - Statins extensively metabolized by CYP3A4: • Lovastatin • Simvastatin • Atorvastatin Diagnosis: • CK: - SAMS <20,000 IU/I - IMNM: 1,000–20,000 IU/I • SAMS clinical index (SAMS-CI) • EMG shows small-amplitude motor-unit potentials with increased spontaneous activity • If statin-associated muscle symptoms (SAMS) fail to resolve after DC statin — then need to consider: immune-mediated necrotizing myopathy (IMNM) • Muscle biopsy if symptoms do not resolve after DC Statin Treatment: • Stop statin • Oral steroid, methotrexate, intravenous immunoglobulin (IVIG), and/or rituximab #SAMS #Statin #muscle #toxicity #myopathy #diagnosis #management #treatment
