In multiple myeloma, a certain kind of white blood cell called a plasma cell begins to multiply abnormally. Normally, plasma cells are responsible for producing antibodies that help fight infections. But in multiple myeloma, excessive plasma cells release unhealthy levels of protein (called immunoglobulin) into the bones and blood. The excessive protein accumulates throughout the body, causing organ damage.
The plasma cells also cause problems inside bones, where they multiply and crowd out normal blood cells. Inside the bone marrow, multiple myeloma plasma cells release chemicals that prompt the body to dissolve areas of bone. This creates weak areas of bone, which are called lytic lesions.
As multiple myeloma progresses, plasma cells begin to spill out of the bone marrow and deposit elsewhere in the body, causing further organ damage.
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