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

## TL;DR

This paper presents a case where muscle biopsy was crucial for diagnosing necrotizing autoimmune myositis when other tests like electromyography and autoantibody testing were negative.

## Contribution

The novelty lies in highlighting the diagnostic value of muscle biopsy in cases where standard autoantibody and EMG tests fail.

## Key findings

- A 73-year-old man with elevated CK and aldolase and muscle weakness was diagnosed with necrotizing autoimmune myositis via muscle biopsy.
- Electromyography and most autoantibody tests were negative despite clinical suspicion of myopathy.
- The case underscores the importance of integrating clinical symptoms with biopsy findings for accurate diagnosis.

## Abstract

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.