What type of immunosuppressant were you prescribed? I recently took prednisone for a little over a week and ended up with some nerve issues afterwards, but not as bad as typical small-fiber neuropathy. The symptoms still haven't resolved.
I don't want to mention it's common name specifically, as this is rare enough that it could be linked to me personally.
It is actually an antibiotic (I'd somehow forgotten that - edited my original comment now!), but once that acts as a immunosuppressant, and it's less-common name is diaminodiphenyl sulfone.