Mechanisms of bone lesions in multiple myeloma.

Lytic bone lesions and hypercalcemia are common features of multiple myeloma; however, they are exceptional in other B-cell malignancies. Myeloma bone involvement is related to an uncoupling process associating an increased osteoclastic resorption with decreased bone formation. Several osteoclast-activating factors such as interleukin-1 (IL-1), tumor necrosis factor, and interleukin-6 (IL-6) are involved in this process. IL-6, the major myeloma cell growth factor, could play a critical role in myeloma-induced bone resorption in association with other known or unknown hematopoietic growth factors, however.