A commentary notes that proper interpretation of this study depends on two factors. First, the diagnosis of myositis must be histologically confirmed; in the study all registry patients had muscle biopsy–confirmed idiopathic inflammatory myositis (IIM). Second, exposure to statin therapy must be accurately classified. This study assessed statin exposure by different methods for cases (drug history in the medical record) and controls (prescription dispensing records), which may have resulted in misclassification bias. It therefore suggests that the association of IIM with statin therapy reported in this study cannot be considered definitive, although these are likely the best data currently available. It stresses that this debilitating adverse effect underscores the importance of prescribing statins only to patients who will clearly have a net benefit.