What is myeloma bone disease? There is a balance in your body between bone eating cells and bone producing cells. Bone eating cells, the osteoclasts, are over-activated when you have multiple myeloma. The myeloma cells are interacting with the cells that are around them and since they sit in the bone marrow, the bone cells are close by. So myeloma cells activate bone eating cells, osteoclasts. We have osteoplasts and we have osteoclasts. And osteoplasts build bone, osteoclasts eat bone, and this happens at the same time in everyone. In myeloma, the bone eating cells are over-activated so it can cause bone destruction. That's the bone disease. Most of the time it happens in areas where there are small plasma cell tumors, they grow and then they cause some bone destruction in a, causing a hole in this area of the bone. Some patients have more diffuse infiltration and there, we're not completely sure, but some patients do more diffuse osteoporosis, meaning a weakening of the whole bone structure. That's also a different kind of way the myeloma can cause bone disease. So osteolytic lesions, focal changes in one area can be caused by myeloma and some patients also have an osteoporosis also caused by the myeloma. So the bone loss can be kind of seen either by a dexa scan or it can be seen in x-rays, for instance in a plain x-ray of the bones, we call that skeletal survey, or it can be seen in a CT scan or also in a head CT. 90% of myeloma patients over the course of their disease develop bone disease. Their severity is very, very different. I have patients who have literally one lesion and that's it and they oftentimes even develop nothing more. And then I have patients who come to me, they have a really severe bone disease. I have patients who lost several inches of height because of fractures. So it can be very, very severe. Even when we do bone marrow biopsy, we feel that the bone is much weaker than if we do it in an MGUS patient, for example.