Don’t Miss Vasculitic Myopathy Without Elevated Creatine Phosphokinase

This report describes an 83-year-old woman who presented with subacute fever and lower limb pain and was ultimately diagnosed with vasculitic myopathy due to microscopic polyangiitis (MPA). Notably, the patient had normal creatine phosphokinase levels despite active muscle involvement confirmed by magnetic resonance imaging and muscle biopsy. Histopathologic findings demonstrated small-vessel vasculitis with fibrinoid necrosis and disruption of the internal elastic lamina. Vasculitic myopathy remains underrecognized, particularly in patients with ANCA-associated vasculitis, as muscle symptoms may occur without creatine phosphokinase elevation.