I don't personally know anything about this, but I know firemanswife21 has posted about it. You can find her site here:
http://www.medhelp.org/personal_pages/user/904511
I was diagnosed with MGUS a couple years ago. I've seen two hematologist/oncologists and both say it's fairly innocuous but needs to be monitored at least annually. (I understand some docs like to run the tests quarterly.) My monoclonal antibody levels have been rising slowly, but are still far below the level that would get someone diagnosed with Multiple Myeloma.
I'm told the only significance is a higher likelihood of developing Multiple Myeloma as I age than someone without MGUS, but still fairly low. The vast majority of people with MGUS never develop MM.
what is a normal IGM level?
I have been diagnosed with MGUS. Monoclonal Gammopathy of Unspecified Significance. I was diagnosed at age 35. I have an abnormal kappa/lambda free light chain ratio but have never had an M-spike. I go to the cancer center, see my hematology/oncologist, they draw blood at the lab, and I have my lab results monitored. First I was monitored every 3months, then 6months, then yearly, and now bi-annually. Nothing terrible has happened, it is just monitored through blood tests, and I have been told that there is at most a 2% chance that I will go on to develop cancer of the blood such as lymphoma or multiple myeloma (of course I can not answer specifically for your situation). In my case, it has been several years of simple monitoring. The hematologist/oncologist I saw believes that my MGUS may actually be evidence of an autoimmune spike, since the part of your blood being monitored relates to immune cell development in your bone marrow. My numbers began at an abnormal level and continuously rose slowly. They still have not reached a level that indicates cancer, and it has been 8 years.
Wikipedia has a fairly good explanation of MGUS. The doctors you see can also give you info, or you can find info on some cancer support websites, or organizations like M.D. Anderson.org. Because it is related to cancer, it seems a bit scary. More people have good luck with simple monitoring than go on to develop any problems, which I hope you will find encouraging. Most importantly, find a doctor you feel you can trust, keep your appointments, and don't worry because you know it is being monitored -- this has been my approach. I hope it helps. I wish everyone improving health!