What is Multiple Myeloma?

Multiple Myeloma is a malignant pathology that affects certain cells of the immune system, causing damage to various organs and tissues. It usually develops in people over 50 and is often accompanied by pain, fractures and bone destruction.

Multiple myeloma is characterized by the proliferation and accumulation in the bone marrow of an abnormal plasma cell clone. Normal plasma cells belonging to the immune system are the result of the maturation of B lymphocytes; the latter are responsible for the production of antibodies (also called immunoglobulins), which protect us from infections.

In most cases of multiple myeloma, a tumor mutation causes the plasma cell to turn into a malignant (myeloma) cell that produces a huge amount of a type of immunoglobulin (called monoclonal immunoglobulin) that is released into the blood. Too much of this paraprotein can cause kidney problems and damage to other tissues and organs. In people with multiple myeloma, abnormal plasma cells make up at least 10% of the cells in the bone marrow. They take the place of other types of blood cells, such as red blood cells, other white blood cells, and platelets, so there aren't enough of these cells to do their job. The affected person can thus become anemic (because they do not have enough red blood cells), bleed easily (because they do not have enough platelets) and contract more infections than normal (because she does not have enough white blood cells).

In multiple myeloma, myeloma cells prevent osteoblasts from making new bone tissue. Myeloma cells also cause osteoclasts to work harder to break down bone, making bones more fragile. The accumulation of myeloma cells in the bone marrow combined with the disintegration of bones by osteoclasts makes bones more fragile and thinner. Weakened bones can break during normal exertion such as walking, lifting, or coughing. Thinning of the bone can also lead to osteoporosis.

Myeloma cells can form tumors in the bones called plasmacytomas. We speak of a solitary plasmacytoma when there is only one tumor in a bone. When there are many plasmacytomas in the bones, the disease is called multiple myeloma. Plasmacytomas can also form outside of bone. These tumors are called extramedullary plasmacytomas.

Tests done to diagnose multiple myeloma include blood and urine tests, biopsy, x-ray, and other imaging tests.

Treatments for multiple myeloma include chemotherapy, stem cell transplantation, and targeted therapy.

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TOUZEAU, Cyrille. myélome multiple.