EPM2A and glycogen storage disease due to glycogen branching enzyme deficiency: Andersen disease (MIM 232500) and adult polyglucosan body disease (APBD; MIM 263570) caused by GBE mutations, as well as Lafora disease due to mutations in malin or laforin proteins (MIM 254780), are all neurological diseases sharing a common neuropathology of malformed glycogen (‘polyglucosan’) accumulation, although their genetic defects affect different aspects of glycogen metabolism.