‘Uncertain significance’ of MGUS
DEAR DR. ROACH: In September 2016, I was diagnosed with IgM MGUS. Repeat bloodwork in November 2017 revealed both IgA and IgM MGUS.
I have no measurable M protein. I have had no fatigue, bone pain or other symptoms. I am a 65-year-old female in good health; I eat carefully, do not drink or smoke and exercise almost every day. Can you comment on my risk of progression?
ANSWER: Monoclonal gammopathy of uncertain significance — MGUS — is a precursor condition to multiple myeloma.
It is of “uncertain significance” because not everyone will progress to myeloma, a cancer of the plasma cells, which make antibodies and live in the bone marrow. MGUS isn’t rare: Three to 4 per cent of the population over 50 has it.
However, because some people do progress, it is important for people with MGUS to be carefully observed over time by an expert in this condition, a hematologist/oncologist.
There are three major laboratory values that can help estimate the likelihood of progressing from MGUS to myeloma. One is the total amount of abnormal M protein in the blood: Those with levels less than 1.5g/dL are at lower risk. People with IgA or IgM subtype are at higher risk than those with just IgG. An abnormal ratio of light chains (kappa and lambda chains or part of the antibody molecule) also predicts greater likelihood.
I looked carefully at the labs you sent me and found low (no) M protein and normal light chain ratio, so you have two favorable and one unfavorable factor, which puts your risk of getting multiple myeloma at about 20 per cent in the next 20 years.
However, your risk may be even lower since your M protein level is so low. In addition to monitoring your labs, you should be on the lookout for symptoms, especially fever, weight loss, fatigue, bone pain or abnormal bleeding.
Your prognosis is good, but people can progress quickly, so you need to be vigilant in getting any symptoms evaluated in addition to regular checkups. Lots more information is available at www.myeloma.org.
Readers may email questions to ToYourGoodHealth@med.cornell.edu