Necrotizing Autoimmune Myopathy With HMGCR Antibodies: An Uncommon Presentation of Autoimmune Myositis in a Middle-Aged Woman Without Known Malignancy, Connective Tissue Disorder, or Statin Therapy

We report an uncommon presentation of necrotizing autoimmune myopathy (NAM) associated with anti-HMGCR antibodies in a middle-aged woman who lacked typical risk factors, including statin use, malignancy, or connective tissue disease. The patient presented with muscle weakness, markedly elevated creatine kinase levels, and muscle biopsy findings consistent with necrosis. Diagnosis of NAM was confirmed through the detection of anti-HMGCR antibodies. Despite the initiation of corticosteroid therapy, the condition progressed rapidly, highlighting the aggressive nature of this form of autoimmune myositis. This case underscores the importance of considering NAM in the differential diagnosis of idiopathic myopathy, even in the absence of common predisposing factors, and emphasizes the need for early detection and individualized treatment strategies.