E5286. Muscle Case-Based Review: Myositis and Its Mimics
  1. Eddy Zandee van Rilland; Stanford University School of Medicine
  2. Kathryn Stevens; Stanford University School of Medicine
  3. Robert Boutin; Stanford University School of Medicine
Myositis is broadly defined as inflammation of skeletal muscle. However, myositis can be due to a wide range of etiologies, including inflammatory conditions, infection, medication, and iatrogenic causes. Additionally, several other muscular pathologies may have similar imaging appearances to myositis. Recognizing specific imaging patterns and clinical presentations of myositis and other myopathies may assist in the accurate diagnosis of these conditions.

Educational Goals / Teaching Points
Provide a review of characteristic imaging findings of myositis and other myopathies through a case-based presentation. Review various pitfalls and myositis mimics that may present similarly to myositis. Discuss common clinical presentations, relevant diagnostic and laboratory testing, potential complications, and treatment options for these conditions.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Imaging plays an important role in the noninvasive evaluation of myositis and myopathy. MRI is the gold standard imaging modality with characteristic muscular edema signal accurately identified on T2-weighted sequences. Additionally, various complications associated with myositis, including myonecrosis, abscess, and osteomyelitis, as well as more chronic changes including muscle atrophy and fatty infiltration, can all be accurately identified with MRI. However, various other pathologies and conditions can have similar imaging appearances to myositis/myopathy, often resulting in a diagnostic dilemma. This presentation will systematically review characteristic imaging findings of the major categories of myositis/myopathy including inflammatory, infectious, drug-induced, and iatrogenic (e.g., radiation therapy). Additionally, various pitfalls and myositis mimics that may have a similar imaging appearance to myositis will be reviewed in a case-based format.

Understanding the characteristic imaging findings and clinical presentations of myositis/myopathy, as well as the various pitfalls and myositis mimics, may assist in the early diagnosis and appropriate management of these patients.