Close relatives of people with multiple myeloma or mono­clonal gam­mop­athy of undetermined significance (MGUS) have an increased risk of having MGUS, according to research published in the journal Blood on Thursday. The research found that parents, siblings, and children of people with multiple myeloma or MGUS are 2.6 times more likely to have MGUS than the general population. An MGUS diag­nosis is asso­ci­ated with an increased risk of developing multiple myeloma.

Scientists at the Mayo Clinic looked at blood serum samples from 911 blood-related, first-degree relatives of people with either multiple myeloma or MGUS. All the study participants were 40 or over.

The researchers then compared the study participants’ rates of MGUS with rates of MGUS found in a pre­vi­ous general health study on 28,000 residents of Olmstead County, Minnesota, who were 50 or older. The researchers used the Olmstead County data to calculate what rates of MGUS they ex­pec­ted to find in the general population.

In both the new Mayo Clinic study and in the older Olmstead County study, clinicians diag­nosed MGUS using a lab test called serum protein electrophoresis. Serum protein electrophoresis is less sensitive than some other tests avail­able for MGUS, such as serum immuno­fix­a­tion and the free light chain assay.

Calculations of absolute risk, on which relative risk figures are based, took age and sex into account.

Doctors could use their findings and the results of any follow-up studies to help determine who is at risk for MGUS, and how to treat people with MGUS, based on whether or not they have a family history of the con­di­tion, the researchers wrote in their paper.

They also wrote that the increased risk they found “implies shared genes and/or en­viron­ment.” They argue in their paper that genetic factors are at play, based on pre­vi­ously done case studies on specific families, and on pre­vi­ous research that found racial differences in MGUS rates, including similar rates of MGUS among people of African descent living in the United States and in Ghana. However, the exact way in which genes contribute to MGUS is not known.

For more in­­for­ma­tion on the increased risk of developing myeloma after an MGUS diag­nosis, please see the related Beacon article. For more in­­for­ma­tion about this Mayo Clinic study, please see the article in the journal Blood.