Therapy with lenalidomide plus dexamethasone-induced bone formation in a patient with refractory multiple myeloma.

Bone disease is a major symptom of multiple myeloma, which results from excessive osteoclast activation and impaired osteoblast function. Novel antimyeloma agents, such as immunomodulatory drugs and bortezomib, alter bone metabolism in patients with this disease. However, recent studies have shown that bortezomib affects bone formation and healing, but immunomodulatory drugs do not. We report a case of refractory multiple myeloma that was treated with lenalidomide combined with dexamethasone (RD regimen). As a result, the patient's myeloma protein expression was markedly reduced, and her hematological profile was improved. However, the treatment also induced tetany by reducing her serum calcium and magnesium levels and elevating her alkaline phosphatase levels. In addition, conventional radiography and computed tomography detected osteosclerosis. These findings suggest that the RD regimen affects bone formation, possibly by activating osteoblasts. This is to our knowledge the first report to suggest that lenalidomide, an immunomodulatory drug, affects osteogenesis, at least in a certain subpopulation of patients with multiple myeloma.