Myopathies: Radiologist's Essential Tips for Clinical, Pathologic, and Imaging Findings

Myopathies are a heterogeneous group of disorders affecting the structure and metabolism of skeletal muscles. The causes of myopathies include hereditary factors (muscular dystrophy, distal myopathies, metabolic myopathies) and acquired factors (infections, endocrine abnormalities, drug-induced causes, idiopathic inflammatory myopathies). Recent advances have enabled clinicians to diagnose myopathies through genetic testing, highlighting the importance of differential diagnoses in clinical practice. Typical symptoms of myopathy include muscle weakness and atrophy. Recognizing symptom onset, progression, affected muscles, and associated symptoms (cataracts, skin rashes, lung issues, joint problems) facilitates accurate diagnosis. Myositis-specific autoantibodies and electromyography are valuable for diagnosing conditions such as dermatomyositis and myotonic dystrophy. Imaging, particularly muscle MRI, is crucial for diagnosis, optimal biopsy site selection, and assessment of disease activity. Muscle MRI allows identification of fat replacement, edema, and inflammatory changes. US and PET/CT offer additional diagnostic and evaluation benefits. Muscle pathologic analysis is essential for diagnosing muscular disorders and assessing structural changes, fiber size variation, necrosis, regeneration, fibrosis, and abnormal structures. Congenital myopathies such as RYR1- and NEB-related myopathies exhibit distinct MRI patterns. Muscular dystrophies, including dystrophinopathies and myotonic dystrophy type 1, display characteristic MRI findings. Limb-girdle muscular dystrophy subtypes reveal specific involvement patterns, leading to diagnosis. Metabolic and mitochondrial myopathies require biochemical testing, muscle biopsy, and genetic analysis. Idiopathic inflammatory and treatment-related myopathies also exhibit distinct imaging features. Continued research and enhanced diagnostic techniques will improve myopathy management. Radiologists must be knowledgeable about the clinical, pathologic, and imaging findings to ensure accurate diagnoses and optimal patient care. ^©RSNA, 2025 Supplemental material is available for this article.