SDC1 and glycogen storage disease VI: In terms of disease characteristics at baseline, 22% of patients had revised International Staging System stage III disease, 33% had high tumor burden (≥ 50% CD138+ plasma cells in the bone marrow), 67% had ≥ 50% tumor BCMA expression, 56% had extramedullary disease, and 22% had high-risk cytogenetics (including del[17p] and t [4;14]).