Plasma cell myeloma

On radiographs, differentiation between myeloma and metastatic skeletal disease may be difficult. The osteolytic lesions in myeloma are uniform and have discrete margins (Fig.1). Particularly characteristic of plasma cell myeloma is a subcortical circular radiolucent shadow associated with erosion of the inner margins of the cortex and sometimes a scalloped and wavy contour throughout the endosteal bone, most commonly occurring in the long tubular bones. Sclerosis generally develops after pathologic fracture, irradiation or chemotherapy of lytic lesions. Often a soft tissue mass forms adjacent to involved bones.

Radionuclide bone scans may be unreliable; plain radiography is often is viewed as a more valuable diagnostic technique. Nevertheless, the radiographic examination is far from ideal for the purpose of monitoring the course of the disease.

CT scanning and MR imaging are valuable in the delineation of lesions. With CT, involvement of the medullary canal (by metastasis, infection or myeloma) is well shown. MR imaging is especially helpful in revealing spinal manifestations. Myelomas are distinguished by differences in contrast between regions of tumour infiltration and background tissue. Special MR imaging sequences, such as short tau inversion recovery (STIR) imaging and fat suppression methods, may lead to improved sensitivity.

Among the rheumatologic manifestations of plasma cell myeloma are neurologic findings (sciatica, brachial neuralgia, peripheral neuropathy), POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M proteins, and skin changes), amyloidosis, gout and infection (lung, urinary tract, osteomyelitis, septic arthritis).

DR/RB