POLG and Mitochondrial myopathy: However, it has been proposed, in a POLG‐linked mitochondrial myopathy, that the neuroinflammation might actually be secondary to the mitochondrial defect, or that these two possible causes could interact or overlap.30 Although these ADEM or ADEM‐like encephalopathies are relatively rare in mitochondrial disease, they represent a significant medical burden.