Classification Criteria

Autoimmune diseases can be classified according to several criteria. One of them is the location of the autoimmune attack. Based on this criterion, autoimmune diseases are distinguished into systemic or organ-specific. Although artificial, this classification scheme is useful for orienting patients and primary care physicians to the appropriate specialist.

Systemic: Affects Many Organs

Systemic autoimmune diseases are those where the autoantigens are found in almost any type of cell in the body, for example the DNA - protein complexes. Consequently, the pathological damage involves many different organs and tissues. Typical systemic autoimmune diseases are rheumatoid arthritis, systemic lupus erythematosus, scleroderma, and dermatomyositis. These diseases are managed by rheumatologists, and in fact the terms "systemic autoimmune disease" and "rheumatic autoimmune diseases" are often used interchangeably.

Organ-specific: Affects One Main Organ

Organ-specific autoimmune diseases are those where a particular organ or tissue is preferentially targeted by the patient's immune system. For example, the thyroid gland in patients with Graves disease, the beta cells of the endocrine pancreas in patients with type 1 diabetes, or the skin in patients with vitiligo.

About 3% of the US population has an autoimmune disease

More Details

How many autoimmune diseases are there?

Many—more than 100. It is difficult, however, to provide an exact number because autoimmune diseases:

  • can challenging to define. Scholars may disagree on the criteria that need to be fulfilled to consider a disease "autoimmune" (i.e, caused by autoimmune mechanisms).
  • are clinically heterogenous, with numerous subtypes and variants. For example, in multiple sclerosis one could distinguish the primary progressive from the relapsing-remitting forms. In thyroiditis one could distinguish the juvenile, the classic, and the form occurring in older persons (known as idiopathic mixedema). Should the different subtypes considered different diseases or should they combined under a single name? As always, definition is critical. Changing how a disease is defined can drastically influence its prevalence.
  • require a vast breadth of knowledge. In order to make a comprehensive list of autoimmune diseases, there has to be somebody who is familiar with all of them and their numerous clinical variances. Quite a difficult task.

With that said, a list of autoimmune diseases has been assembled by the American Autoimmune Related Disease Association. By examining this list you can see that autoimmune diseases can affect pretty much any organ or tissue in the body, so they cast a very broad spectrum of clinical manifestations and patient phenotypes.