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Simple
Explanation:
In
multiple myeloma, as with any cancer, there has been a
mutation of a certain cell. From that single mutated cell a
great many identical cells have grown.
In the case of myeloma, the particular cell that had
the mutation is known as a “plasma cell.”
In every human body there are many health plasma cells.
In the body of someone with myeloma there are both
healthy plasma cells and the mutated plasma cells.
The
mutated (malignant) plasma cells, or myeloma cells,
continuously multiply. Large numbers of myeloma cells form
tumors. Tumors of myeloma cells can grow inside bones or on
the outside of bones. Good
blood cells are crowded out and the bones themselves are often
damaged, leading to fractures.
All
of the myeloma cells are identical and they are all deformed.
They serve no useful purpose because they are
defective. Normal
plasma cells automatically die after a period of time, but the
myeloma cells have lost the ability to die.
Your immune system tries to kill them but is not able
to get the job done.
More
Details:
The
malignant plasma cells, or myeloma cells, have an affinity for
the bone marrow environment where they establish a destructive
relationship with other stromal (bone matrix) cells.
The myeloma cells secrete substances that cause bone
destruction and lead to a further proliferation of the myeloma
cells.
All
of the myeloma cells are identical and are, therefore, called
monoclonal. Depending
on when the mutation took place, for a given individual, the
myeloma cells will produce certain “fragments” of
immunoglobulin (antibodies) that can be used to identify the
type of myeloma.
From
a single mutated plasma cell, trillions of identical myeloma
cells (clones) are eventually created.
Those myeloma cells may form one or more soft tumors
(called plasmacytomas) and/or may infiltrate the marrow inside
certain bones, usually the femur, humeris, pelvis, vertebrae,
ribs, and skull.
Aggregations
of myeloma cells are usually associated with bones, whether
from the inside, the outside or both. The damage to the bone
is known as a lesion. Lesions
show up on imaging studies (x-ray, MRI, scans).
When
the aggregations of myeloma cells occur inside the
marrow-producing bones, the healthy cells of the immune system
(e.g. red blood cells, white blood cells, platelets) are
crowded out. In such cases, the immune system is compromised,
causing increased risk of infections, tiredness, and weakness.
More
Technical Stuff:
The
myeloma cells establish a destructive relationship with bone
remodeling cells called osteoclasts. Myeloma cells produce
soluble signals called cytokines that activate the bone
resorbing osteoclasts. Other
cytokines that are osteoclast activating factors (OAFs) are
lymphotoxin, interleukin-1b (IL-1b) and interleukin-6 (IL-6).
In response, the osteoclasts and other stromal cells
secrete even more IL-6, which stimulates the production of
more myeloma cells.
With
myeloma, there are two malignant cell populations: a slowly
proliferative plasmablast (a plasma stem cell) and a slightly
more differentiated plasma cell that cannot proliferate.
That fact will be important when we get to treatment
options.
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