Disease progression should be measured witha set of indicators, including CRAB criteria (hypercalcemia, renalinsufficiency, anemia, and lytic bone lesions or osteoporosis), M protein level,serum light chain level, and extramedullary disease (mass) detected by imaging.Although M protein is a signal of tumor load in most patients, it is not a goodmeasure for those with non-secretory disease. Here, MYOM2 is linked to glycogen storage disease VI.