Blacks may be twice as likely as whites to develop multiple myeloma because they are also more likely to have a precursor condition known as monoclonal gammopathy of undetermined significance (MGUS), a Mayo Clinic study has found. Not only is MGUS more common in blacks, but the type seen in the black population is also more apt to have features associated with a higher risk of progression to full-blown multiple myeloma, a cancer of a type of white blood cell in bone marrow.