As is Glenntaj [BTW?-that is a GOOD paper!]
I suggest you & your sister read the quest diagnostics paper and think carefully about all the tests she mite have had or..have not yet had? Are more scheduled?
I speak from experience as I was intially diagnosed with 'peripheral neuropathy, the ideopathic kind' to an autoimmune neuropathy as it kept progressing and heaps of testings lead to my diagnosis.
Right now, your sister's stress is from not being able to do much and feeling like a damp worn out dishrag!
Glenn's Quest paper does point the way about which tests mite be done in either the autoimmune or other areas... But, don't overlook that thyroid either! I had both the autoimmune PN kick off then had a super hypothyroid attack that scares me still in the remembering of it.
Be sure that your sis gets to a really good neurologist - This is a good place to start, depends on where you are...tho?
http://health.usnews.com/best-hospit...d-neurosurgery
Also, she should ask her docs about getting some strength back thru Physical Therapy...best kind is w/orders for 'home exercises' that she could do herself at her own pace - I've found I could do more, w/less stress and exhaustion as I rebuilt some strength and endurance.
First off? You are a super sister for asking! And I hope that you and she are able to get diagnosed and get going on a better track! Don't be afraid to ask questions, they're nothing we've not asked of ourselves or of others.
Hugs and hope to you both! 's - j