Muscle diseases represent specific muscle pathology. The characteristic features as hallmarks of diseases have been historically used to diagnose the patients. The “Rimmed vacuole (RV)” (Figures 1) is one of such characteristic features in certain groups of the diseases. This structure consists of the space (vacuole) and purple granules (rim) within myofibers, while the space is sometimes occupied with cytosolic contents indicating that the space is artificially produced during the staining process and the rims have the nature of this pathological hallmark. Ultrastructurally, as discussed later, many autophagic vacuoles and multi-lamellar bodies are observed in RVs.