Autophagic vacuolar myopathy is a subgroup of muscle diseases defined as a condition in which autophagic vacuoles are present as a muscle pathological feature and is caused by abnormality of autophagy in skeletal muscles. There is an autophagic vacuolar myopathy characterized by the presence of specific autophagic vacuoles known as autophagic vacuoles with sarcolemmal features (AVSF). It is referred to as AVSF myopathy and includes Danon disease and related myopathies. Danon disease is an X-linked dominant disease associated with a primary deficiency of lysosomal-associated membrane protein 2 in which severe hypertrophic cardiomyopathy and myopathy develop. Cardiomyopathy is a determinant prognostic factor of this disease, and heart transplantation is still the sole radical treatment. The pathomechanism of AVSF myopathy is considered to be caused by abnormality of autophagy resulting from primary lysosomal dysfunction.