Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The term “autoimmune disease” refers to any disease that is caused by an inappropriate immune response against substances and tissues that are normally present in the body. Autoimmune diseases occur when the immune system mistakenly attacks healthy cells. Up to date, there are more than 80 known disorders belonging to the group of autoimmune diseases. Although these disorders are not curable, their symptoms can be successfully treated. Learn more about autoimmune diseases in this book.