For most people with myeloma, the exact causes are not clear but are thought to be a combination of genetic and environmental factors. Some of the factors that may be implicated are viruses, radiation, exposure to specific chemicals and a generally weakened immune system.

Myeloma is slightly more likely to occur if a family member also has it, which suggests there may be an inherited susceptibility. However, other environmental factors must also be present before myeloma will develop. Although the exact cause of myeloma is not known, quite a lot is known about the factors which are linked with an increased risk of myeloma, although many patients are not affected by any of these:

• Age, gender and race: Myeloma is more common with increasing age. It is about twice as common in people of African origin than in white or Asian people, and three men are diagnosed with myeloma for every two women
• Family history: People with a parent, sibling or child who has myeloma are up to twice as likely to develop myeloma as those who have not
• Obesity: a risk factor for myeloma
• Exposure to toxic chemicals and radiation
• Autoimmune disorders, e.g. rheumatoid arthritis and multiple sclerosis
• Viral infections, e.g. hepatitis, HIV and herpes