For What it's Worth,
I have had serious "Auto-Immune Diseases" since 1986. ( 26 years now...)
There can be ( apparently ) many various and/or sundry "causes" of these MALADIES.
Usually, the Doctors have NO IDEA what might have been the original CAUSE.
Basically....it is when YOUR OWN BODY begins attacking YOU through your own "Immune System".
It ( your immune system ) gets "confused" because ....whatever CAUSED THE PROBLEM ...."looks" very similar to some of your own "tissues"......predominately "joints, muscles, connective tissues", etc. AND...after "killing-off the intruder".....your Immune System ( not knowing that it has completed its job....continues KILLING....you.)
So...the so-called "Medical Community" has FOCUSED upon "relief-of-symptoms".....
rather than "cures". And,usually, this is done by suppressing your own "Immune System"....which creates other problems.
Rheumatology is in its INFANCY yet today.........
....just my 2 pesos worth,
THE Curmudgeon