TNFSF13B and Miyoshi myopathy: APRIL is a member of the tumor necrosis family of ligands, which also includes B lymphocyte stimulator/B cell activating factor (BlyS/BAFF, which is also upregulated in Eμ-xbp-1s MM cells), and these factors have been shown to serve essential prosurvival roles in normal and malignant B lymphocytes.