What is a myeloma?

Myeloma, or multiple myeloma of the bone, is the most common form of hematological cancers, mainly affecting people aged 70 and over. Multiple myeloma affects the bone marrow, where blood cells, namely, red blood cells, white blood cells, and platelets, are produced. 

More precisely, multiple myeloma develops at the expense of a particular type of white blood cells, plasma cells. They are the ones who produce the antibodies, also called immunoglobulins, intended to target intruders (antigen), and thus to fight infections and diseases. 

Due to a dysregulation of the immune system, this plasma cell becomes malignant and multiplies excessively. The condition also brings about malignant proliferation of a plasma cell clone, which produces a single type of immunoglobulin in large quantities, resulting in a monoclonal peak. 

The abnormal plasma cells then invade the bone marrow with various clinical consequences:

• The immune system is weakened. The antibody produced by malignant plasma cells (= the monoclonal protein) is not a functional antibody. In addition, as there are fewer normal plasma cells, there are also fewer normal antibodies. The body then becomes less capable of fighting infections.
• Abnormal (or dystrophic) plasma cells develop to the detriment of other cells. The production of blood cells within the bone marrow is reduced, resulting in the decreased amount of hemoglobin, i.e. anemia.
• Abnormal plasma cells activate cells that destroy bone and disrupt skeletal building mechanisms. Bone pain and pathological fractures arise from this, sometimes even without trauma. Bone destruction can be accompanied by an increased level of calcium in the blood, i.e. hypercalcemia.
• The monoclonal immunoglobulin (the antibody) produced by abnormal plasma cells circulates in the blood. It deposits in the kidneys and can cause kidney failure.