In February 2014, it was announced that a small study had identified a possible bad antibody that was responsible for causing POTS. The auto-antibody is thought to be interfering with adrenergic receptors in the body that interact with certain chemicals the body releases to complete different functions - like constricting a blood vessel or increasing heart rate.
Trying to keep things simple - beta receptors are receptors on a heart cell that interact with epinephrine (adrenaline) that the body releases to increase heart rate. Norepinehrine is a hormone that the body releases to raise blood pressure. The bad antibodies interfere with the ability of these receptors to receive these messages. The following article does a great job explaining things in fairly simple terms - "New Evidence of AutoImmunity in POTS."
There are a lot of doctors who do not believe this is true. We were met with a lot of opposition while searching for answers. But Meghan has responded incredibly to her IVIG auto-immune treatments. I have a hard time believing that it isn't true. Meghan was bit by a deer tick right before her symptoms started. This could have been what caused her body to create antibodies that turned bad. Many, many POTS patients have a heavily taxing virus (such as mono) or other stressful event that triggers these bad antibodies. And now lyme disease (another neurological condition that affects the nervous system) is thought to be a trigger to creating these antibodies. Often times POTS occurs in people that already have a known auto-immune condition, such as lupus or sjogren's. Here is another article published in the medical journal, Lupus, about the findings of those with autoimmune markers and autoimmune disorders in known POTS patients - click here.
POTS syndrome can also occur after a concussion, surgery, pregnancy or other trauma to the body. It is yet unknown if these types of POTS cases are auto-immune.