Remember, HOT T Bone Steak. IL-1 causes severe inflammation and is directly involved in the creation of the lytic lesion.
So I think where I got tripped up is that she does, indeed, have multiple myeloma (so there will be increased serum IgG), but the thing that is actually causing her bones to show the osteoclastic lesions shown in the image is IL-1 (osteoclast activating factor). Weird wording. Thanks NBME.