Role of Vitamin D in rheumatoid arthritis and its association with neuropathic pain: a systematic review and meta-analysis

• Background: Rheumatoid arthritis (RA) is the most common autoimmune disease found in about 1% of adults worldwide. The cause of RA is unknown but there is a combination of genetic and multiple environmental factors dietary resulting in systemic inflammation. Vitamin D not only plays a major role in the regulation of bone mineral homeostasis but also plays a role in in the regulation of the immune response through a different mechanism, these data support a vitamin D deficiency role in the development and progression of RA and other autoimmune diseases. Long-term vitamin D deficiency may lead to decreased immune response and chronic inflammation, which may cause disabling pain. Individuals with vitamin D deficiency often report increased pain perception, which has been referred to hyperinnervation and hypersensitivity in nerve fibers.