What is an autoimmune disorder?

Autoimmune disorders or diseases are very widespread - there are more than 80 serious, chronic illnesses and they all have an effect on one or more of the human organ systems or tissue types. In these illnesses, the body that was designed to protect instead reacts by attacking the body.
Commonly, the organs and tissues effected are:

Red blood cells
Blood vessels
Connective tissues
Endocrine glands such as the thyroid or pancreas
Muscles
Joints
Skin

A list of some of the many autoimmune disorders are listed here for your reference:

Thyroiditis
Lupus (SLE)
Diabetes (Type 1)
Rheumatoid Arthritis (RA)
Sjogren Syndrome
Multiple Sclerosis (MS)
Celiac Disease
Vasculitis

There is currently no cure for autoimmune disorders, although in rare cases they may disappear on their own. Many people may experience flare-ups and temporary remissions in symptoms, others chronic symptoms or a progressive worsening. Treatment of autoimmune disorders is tailored to the individual and may change over time. The goal is to relieve symptoms, minimize organ and tissue damage, and preserve organ function. (From labtestsonline.org)
Symptoms can vary depending on the person involved and the disease.
Some very nonspecific symptoms will often accompany autoimmune diseases, and may include:

Dizziness
Fatigue
General ill-feeling
Low-grade fever

(Information in this post was taken from Medline Plus and other websites.)