There are other plasma cell disorders outside of active myeloma, including monoclonal gammopathy of uncertain significance (MGUS), smoldering multiple myeloma, solitary plasmacytoma and light chain amyloidosis.

In MGUS, abnormal plasma cells make many copies of the same antibody; however, they do not form an actual tumor and do not cause any of the problems seen in multiple myeloma.

Smoldering multiple myeloma, a disease that shows no symptoms of myeloma and is not causing any problems, occurs in those who have a large amount of plasma cells in the bone marrow, a high level of monoclonal immunoglobulin in the blood and a high level of light chains in the urine.

Solitary plasmacytomas are a type of abnormal plasma cell growths that are cancerous and often occur in the bone.

Also a disorder of abnormal plasma cell growth light chain amyloidosis has lower amounts of abnormal plasma cells in the bone marrow compared to multiple myeloma.