An autoimmune reaction may cause pain
Autoimmune dysfunction can cause pain according to a study just published in Neurology by a group of Mayo Clinic researchers. Dr. CJ Klein and his colleagues examined 316 patients who had antibodies to a structure involved in various nerve functions (voltage-gated potassium channel, or VGKC) and discovered that 159 of them had pain as the initial symptoms and 45 of those had pain as the only symptom of this autoimmune reaction. In 19 of these patients pain was localized to face and head, suggesting that some of the headache patients may also suffer from this condition.
The antibodies to VGKC are known to cause excessive excitability of the nervous system. Some of the patients in the study were previously thought to have fibromyalgia (a condition known to be associated with excessive excitation of the nervous system) or psychogenic (not real) pain. This is an exciting discovery since treatment with immune therapies (such as drugs and intravenous immune globulin, or IVIG) relieved chronic pain in 81% of the Mayo Clinic patients. Epilepsy drugs can also help some of these patients.
The difficulty at this point is in identifying patients who should be tested for VGKC antibodies. Probably, we should test patients with chronic persistent pain that does not easily respond to standard treatments. Another difficulty is that the immunosuppressive drugs can have serious side effects, while IVIG is very expensive and can also cause side effects. So these therapies should be reserved for patients in whom pain causes significant disability and in whom potential benefits outweigh the potential risks.