Noteworthily, MGUS is typically followed by the smouldering myeloma (SMM) phase that represents a middle stage between MGUS and MM, and that is characterised by 10–60% clonal BM PCs, and urinary and/or serum M protein at levels more than 500 mg/24 h and 30 g/L, respectively [10]. This evidence concerns the gene MYOM2 and Miyoshi myopathy.