Hello, Sorry, I did not make a deep research on this, but i found this info regarding this tumour marker in blood, beyond CA: "Conditions associated with an increased rate of cell production or destruction, severe infections, viral infections such as CMV (cytomegalovirus), and some conditions that activate the immune system, such as inflammatory conditions and autoimmune disorders, can cause increases in B2M levels." In addition, I understand you can search B2M in CSF (CNS involvement) and in urine (kidney involvement). Thus I was wondering whether PWME do have elevated B2M either in blood, CSF or urine. It seems interesting to me because I am CMV: IgG+ IgM- PCR- Anyway I am been testing for this in order to discard blood CA, suspected by a gastro due to swollen lymph nodes. (Don't think so) Thus, any experiences with elevated B2M in blood, CSF or urine not correlated with blood CA but with ME/CFS ??? (My layman guess is that results are slightly elevated not enough to become concerned about it according to a non-ME/CFS specialist view, as usual ) Thanks!