Inflammatory Myopathy: When Electromyography and Autoantibodies Don't Help the Diagnosis

Inflammatory myopathies (IM) are the most treatable myopathies. Necrotizing autoimmune myositis is a distinct clinicopathologic entity that starts either acutely or subacutely. Autoimmunity is essencial in the pathogenesis of myositis and autoantibodies may be present in more than 50% of patients. We present the case of a 73-year-old man with elevated levels of CK and aldolase, and proximal symmetric muscle weakness and weight loss. The etiological investigation revealed, via muscle biopsy, a necrotizing autoimmune myositis, even though the majority of usual autoantibodies and electromyography were negative. The case demonstrates the importance of combining the patient's symptoms, neurological examination, and analytical changes to corroborate the suspicion of myopathy.