Multiple myeloma is considered to be a hematological cancer. This means that it originates in the blood system. Myeloma cells are abnormal plasma cells that develop instead of the normal plasma cells. These cells do not die as normal blood cells do and, over time, they proliferate and become clumped in different body parts. They also put off a protein that damages the kidneys. Finally, as myeloma cells grow in number, the bone marrow creates fewer healthy red and white blood cells, leading to anemia and serious infections. Several potential causes are under investigation by scientists.
Monoclonal Gammopathy
Long considered a precursor or cause of multiple myeloma, monoclonal gammopathy of undetermined signficance (MGUS) is a condition in which the bone marrow produces abnormal plasma cells. These cells in turn create abnormal proteins, called M proteins. Mayo Clinic explains that while almost everyone who has multiple myeloma had MGUS first, only a small percentage of those with MGUS go on to develop myeloma. MGUS has no noticeable symptoms and is only discovered in a laboratory test. People found to have monoclonal gammopathy are monitored to see if multiple myeloma develops through their lifetime.
Genetic Abnormalities
While most cells have 46 chromosomes, many myeloma cells only have 45 chromosomes. They may be totally or partially missing chromosome 13. In other cases, a part of a chromosome trades places with a part of another chromosome, causing an abnormality that leads to the changes found in multiple myeloma. Scientists have also discovered that individuals with myeloma have either abnormalities or changes in the genes that cause cell division. Changes have also been found in the genes that normally cause cells to die, allowing the myeloma cells to spread instead of dying. These genetic abnormalities may be due to an inherited factor or an environmental exposure may trigger them.
Dendritic Cell Abnormalities
According to the American Cancer Society, people with multiple myeloma have abnormalities in cells in the bone marrow called dendritic cells. This abnormality causes them to produce excessive amounts of a hormone that normally helps plasma cells grow. In excess, however, it allows the myeloma cells to develop.
Viruses
The International Myeloma Foundation reports that the development of certain viruses places individuals at increased risk of developing myeloma. These viruses include a strain of the herpes virus, certain hepatitis (liver) viruses, human immunodeficiency virus (HIV) and others. The viruses themselves may cause some cases of myeloma or the body's immune response to the virus may be responsible.
Toxic Exposures
Scientists are investigating whether toxic exposures cause myeloma. Implicated toxins include wood dust, agent orange, fertilizer and pesticide. Chemicals used in the oil industry or sheet metal work may be responsible for some cases. Finally, radiation may also be a cause of multiple myeloma.
