Another diagnosis???????

The oncologist called. The Mayo Clinic called and said I had Familial Amyloidosis-fibrinogen Alpha-chain type. What???????? This is an inherited disease and I had to have recieved the bummer gene from my Mom or Dad, but neither one had it (but remember how hard it is to diagnose--it can't be diagnosed with a blood test, it has to be a biopsy). Also there is NO history of kidney failure in my family. I then thought about my grandparents. My mom is one of six kids and my dad is one of seven. Still no clue. Three of my grandparents were born outside of the US and the geneology trail gets cold right away, but still there should be some hint of it if it is passed down to 50% of the children. And now I am totally devastated--What in the world have I done to my children and grandchildren? I am shaking and scared and guilty and crying. This is the worst possibe news. I called my friend Kevin and he thought the news was wonderful--familial amyloidosis like I have usually just involves the kidneys, so I don't have all that gruesome stuff to look forward too. And as far as cursing the kids, he said it is very, very rare that the gene expresses itself.
I am having a hard time a hard time accepting this. This is a very, very rare type of amyloidosis--we estimate that there are maybe fifty people in the US with this. I can't figure out if it gets passed 50% of the time to your offspring, and doesn't manifest until you're in your 50's, why don't more people have it. Lon and the doctors understand it, but I don't.