Since the early discoveries on the role of Syndecan-1/CD138 on the MM cell biology, two fundamental notions have progressively been consolidated: Syndecan-1/CD138 is indeed a reliable biomarker in MM, non-Hodgkin’s lymphomas, a number of plasmacytoid neoplasia and CLL-B and different isoforms of the proteoglycan are expressed in different B cell malignancies. The gene discussed is SDC1; the disease is Miyoshi myopathy.