Is polyneuropathy a life threatening disease? can my rheumatologist cure this disease or should i see neurologist?

Not usually: The word polyneuropathy describes symptoms you have and findings on exam and diagnostic testing but does not tell you the cause, which is needed to determine the prognosis. There may not be a cure. A rheumatologist may be comfortable working up the disorder or may enlist the help of a neurologist. Intervention depends on the cause of the symptoms and may involve both specialties.

It depends: To a certain extent, it depends on the underlying cause of the polyneuropathy. Some causes are more responsive to treatment than others. Ask your rheumatologist the same questions you ask here.

Usually not: You would want to see a neurologist, I'd think. There are many, many causes of peripheral neuropathy. In the US, diabetes is the number one cause. Some people even have two things contributing to their neuropathy, so testing is important even in diabetics.