"Unknown significance".. not always!
In my case the MGUS causes the nerve damage, because the IgM produced by the abnormal number of B-cells binds to a protein called MAG (Myelin Associated Glycoprotein), part of the myelin sheath that can be described as the insulation around the nerves, marking it for the macrophages to destroy like they do when a bacteria or virus invade the body.
Normal B-cells “die” when they have produced the IgM they are supposed to, but in my case, they don’t die, but go on producing their “flawed” IgM. It’s true what Keith says that in most cases MGUS doesn’t do any harm if it doesn’t develop into myeloma, but I have been in contact with several MGUS patients that have great problems with fatigue.
So I think that in many cases the “Significance” is not as “Unknown” as the name suggests! Underneath my signature I have the complete name of my diagnosis, where the PDN stands for “Proteinaemic Demyelinating Neuropathy”.
The reason why Rituxan was the right treatment for me is that this chemo-drug kills off the B-cells, and the the amount of IgM goes down and the attack on my myelin sheath is halted. Then it slowly but surely grows back!:)