I’m so sorry it took so long to get a diagnosis and then such difficult news! Since this is probably autoimmune you might find others with similar issues on that group.

I hope you will find good physical therapists and occupational therapists to assist you through any difficulties you might have. Just like doctors, there are really good ones and not so caring ones. I’m not sure what the protocol is for PT, but I wouldn’t hesitate to start early as the therapist may be able to help preserve as much muscle function as possible and/or recruit other muscles to assist those that have weakened.