ch as a lack of B vitamins - Alcoholism, often through poor dietary habits and vitamin deficiencies - Autoimmune diseases like lupus, rheumatoid arthritis, or Guillain-Barre syndrome - Tumors, which can press up against nerves - Diseases and infections, such as kidney or liver disease, Lyme disease, HIV/AIDS, or an underactive thyroid (hypothyroidism) - Exposure to toxins, such as heavy metals or