Autoimmune Necrotizing Myositis (NAM)/Immune-Mediated Necrotizing Myositis (IMNM), a progressive myopathy, lacks skin lesions and exhibits unique pathologic traits. Risk factors like statin use and malignancy are implicated, while most IMNMs are idiopathic. Manifesting as insidious proximal muscle weakness, they often lead to difficulties in functional tasks early in the disease. This article presents a case of a 65-year-old male with Immune-Mediated Necrotizing Myopathy exhibiting atypical needle electromyography findings with widespread denervation in multiple limbs in a proximal distribution. The patient complained of bilateral hip/thigh weakness and symmetric numbness in the feet, among other symptoms. Evaluation revealed significant findings including elevated creatine kinase (CK) levels, Anti 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) antibodies, and abnormal electromyography indicating motor axon/myopathic involvement. Urgent referrals led to diagnosis confirmation and subsequent immunotherapy. This case highlights the challenges in diagnosing myopathies, emphasizing the importance of comprehensive patient history and clinical examinations. Electrodiagnostic studies complement clinical assessments, aiding in confirming myopathy and suggesting alternative diagnoses.Statin-induced necrotizing immune myopathy, associated with anti HMG-CoA antibodies, poses serious risks, warranting statin cessation and cancer screening.Recognizing when to refer patients promptly is crucial to minimize diagnostic delays.Prognosis for IMNM patients is challenging, with persistent weakness despite intensive treatment, emphasizing the need for a multifaceted approach in diagnosis, management,and patient care. Understanding clinical presentations, utilizing diagnostic tools judiciously, and recognizing risk factors are vital for optimizing outcomes in these complex neuromuscular disorders.
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