Myeloma

Pathophysiology

Myeloma bone disease is due to the overexpression of receptor activator for nuclear factor κ B ligand (RANKL) by bone marrow stroma. RANKL activates osteoclasts, which resorb bone. The resultant bone lesions are lytic (cause breakdown) in nature. They are best seen in plain radiographs, which may show "punched-out" resorptive lesions (including the "raindrop" appearance of the skull on radiography).