Electron Microscopy (EM) is a technique that produces high-resolution images of biological and non-biological specimens. Transmission electron microscopy is used to evaluate structural muscle components such as sarcolemma, sarcomere, nucleus, mitochondria, and blood vessels.
Therefore, electron microscopy is useful for the diagnosis of congenital myopathy (specially recommended for the diagnosis of core myopathies like nuclear filamentous inclusions, rod bodies, tubuloreticular bodies), myofibrillar myopathy, mitochondrial myopathy (increased/enlarged mitochondria, altered cristae, paracrystalline inclusions), inflammatory myopathy, storage disorders (glycogen in membrane bound vacuoles, lipid vacuoles) and metabolic disorders.
Among the inflammatory myopathies, electron microscopy is useful to confirm sporadic inclusion body myositis. Dermatomyositis can cause tubuloreticular inclusions in the cytoplasm of capillary blood vessel endothelial cells. These are considered early findings during disease evaluation, as they may be discovered before the inflammatory infiltrate appears.
Dr. Meenakshi Swain, discusses in detail about the role of electron microscopy in muscle pathology.