The multiple myeloma is a cancer which forms in the type of white blood cell known as a plasma cell. It is known fact that plasma cells can help you in the fight against infections by making antibodies which they recognize and attack germs.
The multiple myeloma is causing cancer cells to accumulate in the bone marrow, where they crowd out healthy blood cells.  The cells are not producing helpful antibodies. Instead, the cancer cells are producing abnormal proteins which can lead to complications. The treatment for multiple myeloma is not always necessary for people who are not experiencing any signs or symptoms. Those people who have multiple myeloma who need a treatment can find many different types of treatments that aim to control this disease.
The signs and symptoms of the multiple myeloma can vary. In the early stage of this disease, there may be no signs and symptoms. When the signs and symptoms of the multiple myeloma happen, then they can include:
Weakness or numbness in your legs
Mental fogginess or confusion
Loss of appetite
Bone pain, especially in your spine or chest
You should visit your doctor if you have any persistent signs and symptoms which worry you.
It is not known what the cause for the multiple myeloma is. Doctors know that the multiple myeloma begins with the abnormal plasma cell in the bone marrow, which is the soft and blood – producing tissue which falls in the center of most of your bones. The abnormal cell is multiplying very quickly. The cancer cells do not mature and they do not die as the normal cells do, they accumulate, eventually overwhelming the production of the healthy cells. 
In the bone marrow, the myeloma cells crowd out the healthy white blood cells and the red blood cells which is leading to fatigue and an inability to fight against infections. The myeloma cells are continuing in their attempt to produce antibodies, as the healthy plasma cells do, but the myeloma cells are producing abnormal antibodies which the body cannot use. The abnormal antibodies (which are known as M proteins or monoclonal proteins) build up in the body and they cause problems, such as damage to the kidneys. Also, cancer cells can cause damage to the bones which is increasing the risk of broken bones.
There are some factors which can increase your risk of this myeloma, such as
Personal history of a monoclonal gammopathy of undetermined significane (MGUS): There are some studies in which are noticed that every year about 1% of people who suffer from MGUS in the USA develop the multiple myeloma .
Increasing age: It is noticed that the risk of multiple myeloma is increasing as you are getting older. Most people are diagnosed with multiple myeloma in their mid 60s .
Family history of multiple myeloma: There are some studies in which are shown that if a parent, brother or sister has a multiple myeloma, then you have increased risk of developing this disease. 
Male sex: It is noticed that men are having more chances of getting this disease compared to women. 
Black race: There are some studies in which are noticed that black people have two times more chances of getting multiple myeloma compared to white people. 
There can be complications caused by the multiple myeloma, such as
Low red blood cell count (anemia): The myeloma cells crowd out normal blood cells, so the multiple myeloma can cause anemia and other blood problems. 
Frequent infections: There are some studies in which are said that the myeloma cells can inhibit your body’s ability to fight against infections.
Reduced kidney function: It is noticed that this myeloma can cause problems with kidney function, such as kidney failure. The higher levels of calcium in the blood are related to eroding bones which can interfere with your kidney’s ability to filter the waste of your blood. It is noticed that the proteins which are produced by the myeloma cells can cause similar problems. 
Bone problems: The multiple myeloma can affect your bones which is leading to broken bones, thinning bones and bone pain. [1,2]
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