Multiple Myeloma

Multiple myeloma is a malignancy of clonally expanded plasma cells. These abnormal plasma cells accumulate in the bone marrow and produce one monoclonal immunoglobulin, or isolated light chains, rather than the diverse antibodies made by healthy plasma cells. The clone damages the patient in several connected ways. Marrow infiltration suppresses normal blood-cell production, producing anaemia and sometimes broader cytopenias. Myeloma cells stimulate osteoclast activity, so bone is resorbed faster than it is rebuilt. The result is osteolytic lesions, vertebral compression, pathological fractures, and release of calcium into the bloodstream. Filtered monoclonal light chains can form tubular casts and injure the kidneys; dehydration and hypercalcaemia further reduce renal function. At the same time, normal immunoglobulin production is suppressed, leaving the patient vulnerable to infection even when the monoclonal protein level is high. The familiar CRAB pattern—hyperCalcaemia, Renal impairment, Anaemia, and Bone lesions—is therefore a consequence map, not merely a memory aid. A patient may also develop hyperviscosity from a large circulating monoclonal protein, with visual disturbance, neurological symptoms, or bleeding; these findings require urgent assessment.