Abstract 5002: Persistent Structural Injury in Skeletal Muscle of Patients with Statin-Associated Myopathy
Muscle pain and weakness are frequent complaints in patients treated with HMG Co-A reductase inhibitors (statins). The extent to which this reflects underlying muscle injury is unknown. Biopsies were obtained from the vastus lateralis from 30 patients with clinically diagnosed statin-associated myopathy, 19 were on active statin therapy (group M+S), and 11 had discontinued statin therapy prior to the biopsy (group M−S; median duration of discontinuation 54 weeks). 18 subjects who never received statins and had no muscle complaints served as controls. Muscles were classified as injured if ≥2% of muscle fibers demonstrated damage as assessed on plastic-embedded, semi-thin sections in the light microscope. No muscle injury was observed in the control subjects. Significant muscle injury was observed in 10 of 19 patients in the M+S group (p<0.001 vs control) and in 8 of 11 patients in the M−S group (p<0.001 vs control; p=NS vs M+S). Injury was characterized by vacuolization of T-tubules and detachment of myofibrils. The degree of damage was correlated with the dose of statin administered. Only 1 patient had a circulating level of creatine phosphokinase (CPK) elevated more than 10-times normal. The majority of patients with clinically diagnosed statin-associated myopathy had evidence of muscle injury, regardless of whether they were currently receiving treatment or not. These findings support the idea that myopathy in statin-treated patients reflects structural muscle damage, and further, that lack of elevation of circulating CPK levels does not rule out the presence of significant structural muscle injury.