I was told it was related to my on going issues with low mainly platelets I seem to remember or it may have been that I have a couple of viruses that plague me.CMV and Parvio b19. I'm on folic acid for it but actually it wasn't my team at Mayo but my GP that noticed it and put me on Folic acid and it's come down quite a bit . About the time I was having major issues with low blood counts and parvo was positive it actually got up to the 400s. But we seem to have both the viruses and that level stable for the past year or so. So I don't have a definite answer as why but I know it's related somehow to being immusupprest and those 2 viruses cmv and parvo b19 which were both positive about that time they were high. The folic acid has helped a lot and they keep me on a low dose Tacrolimus to alow my immune system to help with the viruses.