Autoimmune Disorders Defined

An autoimmune disorder occurs when the body’s immune system attacks and destroys healthy body tissue by mistake. There are over 80 types of autoimmune disorders, and rheumatology disease such as Rheumatoid Arthritis (RA) is an autoimmune disease. Autoimmune disease is a result of when something misfires in your immune system. Instead of attacking threats, your very own immune system goes after you.

Autoimmune rheumatic diseases (ARDs) are a diverse group of conditions that primarily affect the joints, bones, muscle, and connective tissue (see Sidebar).  They can be especially challenging to diagnose during early stages, often presenting with nonspecific symptoms and signs that may flare and remit. However, early diagnosis is important to improve outcomes for patients.

 The majority of rheumatic diseases are due to an autoimmune response,whereas others (eg, gout and osteoarthritis) have different pathophysiology.

The overall prevalence of autoimmunity in the general population is approximately 3% to 5%.  Women get autoimmune diseases at a rate of more than twice that of men (6.4% of women compared to 2.7% of men). 

Different autoimmune diseases can occur at different times in a person’s life. However, women are most commonly diagnosed with an autoimmune disease when they are between 14 and 44 years old.

Some ARDs, such as SLE (Systemic Lupus Erythematosus), have a genetic component and others can be triggered by infections or environmental factors.  However, the cause of an ARD in a specific individual usually cannot be determined.

What are the causes of autoimmune disease?

The blood cells in the body’s immune system help protect against harmful substances. Examples include bacteria, toxins, viruses, cancer cells, and blood and tissue from outside the body. These substances contain antigens. The immune system produces antibodies against these antigens that enable it to destroy these harmful substances.

When you have an autoimmune disorder, your immune system does not distinguish between healthy tissue and potentially harmful antigens. As a result, the body sets off a reaction that destroys normal tissues.

The exact cause of autoimmune disorders is unknown. One theory is that some microorganisms (such as bacteria or viruses) or drugs may trigger changes that confuse the immune system. This may happen more often in people who have genes that make them more prone to autoimmune disorders.

An autoimmune disorder may result in:

  • The destruction of body tissue
  • Abnormal growth of an organ
  • Changes in organ function.


An autoimmune disorder may affect one or more organ or tissue types. Areas often affected by autoimmune disorders include:

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


A person may have more than one autoimmune disorder at the same time. Common autoimmune disorders include:


SOURCE: National Library of Medicine’s MedlinePlus database.