I read somewhere once that the increased risk is as much as 50% higher
than if you didn't already have 1 autoimmune disease.  That was designed
to sound horrific, to scare people.  Look at it in real terms:  The
incidence rates are typically less than 1 in 100 for having an autoimmune
disease, that is all of them put together, but suppose it is your
effective risk.  Now, if you have 1 autoimmune disease, and your risk
of having a second increases your risk by 50%, that means 1.5 in 100
people with 1 autoimmune disease will have more than 1.  In other words,
instead of 1 in 100, it is 1.5 in 100.  Those are just NUMBers, though.
I certainly empathize with those that are "blessed" with more than one.
A thing to know is that because you might have antibodies against your
thyroid, say, does NOT mean that they are going to turn against something
else when they are done.  We aren't talking garden slugs here that will
eat anything in their path.  Thyroid antibodies attack the thyroid.  Period.
If your immune system is shut off, such as with AIDS or immunosuppressing
drugs, that is a different game....and all the more rare as a natural
phenom.  
--
Ted Huston    Newsgroup hypodermic (pain in the a**)  dr...@umich.edu
"Mrs Brown only THINKS she's ill, but believe me she is nothing but a
hypodermic."  -- Genuine letters sent to the DHSS (UK)