# Interpreting a Delayed Workup of Idiopathic Inflammatory Myopathy

## TL;DR

This paper presents a case of a man with delayed diagnosis of a muscle disease, highlighting the challenges in diagnosing inflammatory myopathies with suboptimal biopsies.

## Contribution

The paper provides a detailed diagnostic workflow and emphasizes the difficulty in diagnosing inflammatory myopathies with delayed workups and poor-quality biopsies.

## Key findings

- A 70-year-old male presented with dyspnea and muscle weakness, with creatine kinase levels and imaging indicating chronic myopathy.
- Muscle biopsy was suboptimal but suggested several possible diagnoses, including sIBM, IMNM, and AS.
- Electron microscopy confirmed tubulofilamentous inclusions, leading to an accurate diagnosis.

## Abstract

Idiopathic inflammatory myopathies are a widely heterogeneous group of muscle diseases and encompass multiple clinicopathologic entities. Our case presentation describes a 70-year-old male who presented with progressively worsening dyspnea, along with worsening proximal muscle weakness in the bilateral lower extremities. Extensive clinical evaluation revealed a creatine kinase level of 105 IU/L, severe and chronic widespread myopathy seen on electromyography (EMG), and asymmetric but widespread muscle atrophy with fibro-fatty replacement seen on ultrasonography. Muscle biopsy specimen from the left deltoid was suboptimal but demonstrated characteristics that could be consistent with several clinicopathologic diagnoses, including sporadic inclusion body myositis (sIBM), immune-mediated necrotizing myositis (IMNM), antisynthetase syndrome (AS), and direct toxin-induced myopathy. Electron microscopy revealed tubulofilamentous inclusion associated with autophagic debris, finally rendering an accurate diagnosis. This case summary highlights the testing workflow required to diagnose a patient with an inflammatory myopathy and outlines the difficulty in establishing a diagnosis when the workup for an inflammatory myopathy is delayed and the muscle biopsy is suboptimal.