What Causes Peripheral Neuropathy In A Patient With Diabetes?
MGUS certainly related, sugar possibly.
Detailed Answer:
I read your question carefully and I understand your concern.
Sugar can have an effect on neuropathy. Diabetes which is associated with high blood sugar levels is in fact the most common cause of neuropathy. Of course that depends also on your metabolism, eating sugar doesn't automatically transfer into high blood sugar level, it depends also on insulin production and responsiveness of the tissues to insulin action. But it is a sign of alarm which should prompt into testing for diabetes if not already done so recently.
As for the MGUS diagnosis, yes it can very much be related to your neuropathy. MGUS can cause a number of peripheral nervous system disorders, polyneuropathy being one of them. Signs of neuropathy may actually be present for some time before the diagnosis of MGUS has been made. The fact you didn't respond to Gabapentin may be related as well, as MGUS related neuropathy is often less responsive to medication for neuropathic pain like gabapentin.
I remain at your disposal for other questions.