TNFSF13B and Miyoshi myopathy: The interaction between MM cells and the BM microenvironment leads to considerable secretion of cytokines and growth factors, including IL‐6, insulin‐like growth factor (IGF‐1), B‐cell activating factor (BAFF), a proliferation‐inducing ligand (APRIL), tumor necrosis factor‐α (TNF‐α), and vascular endothelial growth factor (VEGF).41