Objective(s): In this study, we aimed at evaluation of electrophysiological and histopathalogical
characteristics of statin‐induced muscle injury as well as clinical features of patients who develop this
condition in terms of frequency and pattern of evolution.
Materials and Methods: Forty patients (age 39‐74 years) including 25 subjects with type 2 diabetes
mellitus, 9 with cardiovascular diseases and 6 with hyperlipidemia, who were receiving atrovastatin
40 mg/day for variable period, were studied. Thirty three healthy subjects (age 31‐74 years) served as
control group. Creatine phosphokinease level, thyroid function, motor unit potential parameters and
muscle fiber conduction velocity of biceps brachii and tibialis anterior muscles were measured.
Results: Creatine phosphokinase level was elevated in statin users, particularly in those with diabetes
mellitus. Less than 50% of statin users experienced symptoms related to muscle injury. Muscle fiber
conduction velocity of the biceps brachii muscle was significantly reduced. Statin users with diabetes
mellitus showed significant changes in electrophysiological parameters as compared to those with
cardiovascular diseases and hyperlipidemia. Muscle biopsies showed muscle fiber variation in size,
fibrosis and mild inflammatory cell infiltration. Immunohistochemical evaluation of muscle biopsies
showed positive expression of Bcl‐2 and one patient showed positive P53 immunohistochemical
expression with elevated level of creatine phosphokinase.
Conclusion: Atorvastatin increased average creatine kinase, statins produce mild muscle injury even in
asymptomatic subjects. Diabetic statin users were more prone to develop muscle injury than others.
Muscle fiber conduction velocity evaluation is recommended as a simple and reliable test to diagnose
statin‐induced myopathy instead of invasive muscle biopsy.
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August 2015
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