10 things to know about AUTOIMMUNE DISEASES

March is Autoimmune Awareness Month-learn about these mysterious (and increasingly common) conditions.

- Gina Way

1 Autoimmune disorders affect millions.

It is estimated that up to 50 million people in the U.S. live with an autoimmune disease, making it the third most prevalent disease category. These disorders are on the rise for reasons experts don't yet fully understand; one possible reason may be increased exposure to environmental toxins.

Autoimmune disorders can affect any organ (for example, autoimmunity in the pancreas causes type 1 diabetes) or can create systemic inflammation (as with lupus). Autoimmune diseases can appear at any stage of life.

2 THE CAUSE CAN BE A MYSTERY.

Autoimmunity happens when the body's immune system, which fights off foreign invaders like bacteria and viruses, attacks itself. Why this happens in some people and not others is unclear, but "we do know that genetics and the environment-including toxins, bacteria, and viruses-are critical components," explains Felipe Andrade, M.D., Ph.D., an associate professor of medicine in the division of rheumatology at Johns Hopkins University School of Medicine.

"You may have a genetic predisposition to autoimmunity and also contract a virus that could trigger it, but then you may never end up developing an autoimmune disease," he says, while someone else may develop autoimmunity without having a predisposition to it or any viral exposure.

3 Inflammation plays a key role.

All autoimmune diseases have one thing in common: inflammation.