Autophagic vacuolar myopathy

Autophagic vacuolar myopathy, or AVM, is a group of rare genetic muscle disorders that share features on muscle biopsy: an excess of autophagic vacuoles whose membranes have the character of the muscle cell membrane. Five types were recognised as of 2019. Symptoms worsen over time, beginning with trouble picking up small objects and advancing to difficulty walking, and onset ranges from early childhood to late adulthood. Danon disease results from mutation of the LAMP2 gene and X-linked myopathy with excessive autophagy from mutation of VMA21, which slows fusion of autophagic vacuoles with lysosomes and leads to muscle breakdown. Diagnosis relies on genetic testing together with clinical history.