Started a few years ago as a neuroimmune disorder with periodic and horrific OCD, depression, muscular failures, inability to concentrate, ... Much of that has passed, but it has morphed into ME/CFS. That still still seems triggered and/or related to an underlying neuroimmune issue. When the immune system kicks up, an autoimmune condition also ramps up and causes inflammation in the brain (among other things), which in turn leads to all sorts of symptoms. She used to run half marathons but now a flight of stairs are a big challenge.

None of it is well understood and there aren't good treatments. Some treatments help some people, but it is kind of hit or miss and most of the potential treatments aren't cheap.

It is actually similar in many ways to some forms of long covid, so bizarrely, covid and subsequent research may lead to better therapies that could help her as well. At least that's the hope...