There are more than 100 autoimmune diseases, and they mostly strike women. Here's what to know

Our immune system has a dark side: It’s supposed to fight off invaders to keep us healthy. But sometimes it turns traitor and attacks our own cells and tissues.

What are called autoimmune diseases can affect just about every part of the body — and tens of millions of people. While most common in women , these diseases can strike anyone, adults or children, and they’re on the rise.