Autoimmune Disease Classifications

The Autoimmune Registry is a resource for information on autoimmune conditions. An autoimmune condition is defined as a disease, syndrome, or comorbidity that is caused when the immune system malfunctions, which we also refer to as immune system dysfunction.

Diseases, syndromes, and comorbidities are often mixed together, but they are different from a scientific perspective. This page describes the difference.

Autoimmune conditions can be further classified by the specific organ they affect, or if they affect many organs. For example, Type 1 Diabetes is an organ-specific disease because it primarily affects beta cells in the pancreas. But when an antibody attacks cells that appear in many different organs and tissues, it is called systemic, since it affects the whole body. Lupus is an example of a systemic autoimmune disease.

Diseases

An autoimmune disease is one that is caused when the immune system attacks healthy cells in your body. To be classified as a disease, ARI looks for scientific articles that demonstrate that the immune system has antibodies that attack healthy cells. Autoimmune Thyroditis was the first disease where antibodies designed to destroy thyroid cells were found.  However, it is often difficult to find cell-specific antibodies, so there are many diseases that are not accepted as autoimmune by the medical community because the cell-specific antibodies have not been detected in patients.

At least, not yet.

Overlaping Diseases, Syndromes & Subtypes

An autoimmune syndrome is a collection of signs or symptoms that appear together. A syndrome may be caused by immune system malfunction or something else (genetics, environment).  Chronic Fatigue Syndrome is a good example.

A subtype is used when a disease appears in different ways among different people. They share enough symptoms in common to consider them as having the same disease, but the differences in severity, symptoms, and outcomes lead scientists to define subtypes. For example, jejunoileitis is a subtype of Crohn's disease that causes inflammation in the jejunum.

When a person suffers from 2 or more autoimmune diseases or symptoms at the same time, and the combination is common enough to affect enough people, we call it an overlap syndrome.  Felty Syndrome, marked by rheumatoid arthritis, an enlarged spleen (spenomagaly) and a low white blood cell count (called neutropenia or granulocytopenia)  is an example of an overlap syndrome.

Comorbidities

An autoimmune comorbidity is a medical condition that happens at the same time as an autoimmune disease. For example, the probability that women with endometriosis will have  hypothyroidism is 9.6% versus 1.5% for women who do not have endometriosis. ARI therefore defines endometriosis as a comorbidity. We believe comorbidities could provide opportunities for better understanding the cause of autoimmune diseases, and that research on treatments for comorbid conditions can help patients cope with autoimmune diseases.