You can treat HUS with plasmapheresis, I think just because not much works anyway. Im not sure how many antibodies there are to clear from the serum in this condition though.
I also associate plasmapheresis with autoimmune neuropathic disorders (Guillian-Barre, severe myasthenia gravis, etc.)
Key thought is that any life threatening autoimmune condition can (and should) probably be treated with plasmapheresis