Bone pain is the most common symptom in myeloma, affecting nearly 70% of patients. The pain usually involves the back and ribs, and unlike the pain of metastatic carcinoma, which often is worse at night, the pain of myeloma is precipitated by movement. Persistent localized pain in a patient with myeloma usually signifies a pathologic fracture. The bone lesions of myeloma are caused by the proliferation of tumor cells, activation of osteoclasts that destroy bone, and suppression of osteoblasts that form new bone. The osteoclasts respond to osteoclast activating factors (OAF) made by the myeloma cells [OAF activity can. | Chapter 106. Plasma Cell Disorders Part 4 Bone pain is the most common symptom in myeloma affecting nearly 70 of patients. The pain usually involves the back and ribs and unlike the pain of metastatic carcinoma which often is worse at night the pain of myeloma is precipitated by movement. Persistent localized pain in a patient with myeloma usually signifies a pathologic fracture. The bone lesions of myeloma are caused by the proliferation of tumor cells activation of osteoclasts that destroy bone and suppression of osteoblasts that form new bone. The osteoclasts respond to osteoclast activating factors OAF made by the myeloma cells OAF activity can be mediated by several cytokines including IL-1 lymphotoxin VEGF receptor activator of NF-kB RANK ligand macrophage inhibitory factor MIP -la and tumor necrosis factor TNF . However production of these factors decreases following administration of glucocorticoids or interferon IFN a. The bone lesions are lytic in nature and are rarely associated with osteoblastic new bone formation. Therefore radioisotopic bone scanning is less useful in diagnosis than is plain radiography. The bony lysis results in substantial mobilization of calcium from bone and serious acute and chronic complications of hypercalcemia may dominate the clinical picture see below . Localized bone lesions may expand to the point that mass lesions may be palpated especially on the skull Fig. 106-4 clavicles and sternum and the collapse of vertebrae may lead to spinal cord compression. Figure 106-4 Bony lesions in multiple myeloma. The skull demonstrates the typical punched out lesions characteristic of multiple myeloma. The lesion represents a purely osteolytic lesion with little or no osteoblastic activity. Courtesy of Dr. Geraldine Schechter with permission. The next most common clinical problem in patients with myeloma is susceptibility to bacterial infections. The most common infections are pneumonias and pyelonephritis and the most frequent pathogens
