When medicine grew up in the middle ages, physicians had to divide diseases into various kinds and various categories. The only way they could classify diseases was anatomically, that is, where does the disease occur? Physicians later divided themselves into doctors who were interested in diseases of the lungs, and other doctors who were interested in diseases of the skin, and other doctors were interested in disease of the intestinal tract or the reproductive tract or the urinary tract. Most medicine is still organized on the basis of the anatomy of the disease, on where the disease occurs. You go to a heart specialist (a cardiologist) if you have heart disease, to a neurologist if you have nervous system disease, to a dermatologist if you have a skin disease, and on and on. The medical community organized itself that way because that's all the doctors knew. They didn't know what caused disease, but they knew where it occurred. But starting with Louis Pasteur about a hundred years ago, a change occurred. For the very first time we began to understand why disease occurs--not where it occurs, but why it occurs. And when we speak of why disease occurs, we speak of something else, and that is what we call etiology.

     Etiology means cause, why the disease occurs. If we are concerned with curing disease and possibly even preventing disease, the etiology is the most important information. Why have we been able to control so many infectious diseases? Because we now know the bacteria and the viruses and the parasites that cause these diseases, and we can develop antibiotics and other drugs that will specifically attack that organism. Discovering the etiology has allowed medicine to progress to its present state where we can successfully treat and even cure many diseases.

     Within the lifetime of most of us, we have ways of effectively treating infectious disease. Until World War II, until antibiotics were introduced, we did not have methods that cured disease. We had treatments that alleviated the symptoms of disease, but we really didn't cure disease. With the introduction of antibiotics--penicillin, streptomycin, and other substances--we now have a way of treating. And that's why it is so important to understand etiology.

     Here are a few other groups of diseases which are now defined by their etiology. Allergies are an example. If you have an allergy, it doesn't matter whether it's an allergy of the nose, that is, hay fever, whether it's in the lungs, asthma, or whether it's atopic dermatitis, a skin disease. You may go to an allergist because all of these diseases have the same etiology. They have different anatomies, but they have the same etiology. That's the way progress is being made by bringing together diseases with the same etiology.

     Autoimmunity is an etiology: it is a cause of disease. Anatomically, autoimmune disease is very diverse; and that's why we see specialists in so many areas of medicine studying autoimmunity. They may be rheumatologists who are interested in joints; they may be dermatologists who are interested in skin; they may be cardiologists who are interested in the heart; they may be gastroenterologists who are interested in the gastrointestinal tract. But the common etiology for all of these disease--for Crohn's disease of the gut; for lupus of the skin; for rheumatoid arthritis of the joint--the common etiology that brings together all of these diseases is autoimmunity.

     A major aim of the American Autoimmune Related Diseases Association is to help us to understand that all of these diseases, diverse as they are, in their anatomical location, in their clinical manifestation, are related because they have the same etiology; they are all caused by autoimmunity. In my opinion, the only way we're going to develop really effective treatments will be to treat the cause of the disease, not the symptoms. The symptoms are late; the symptoms are at the end of the train of events. We want to get on the train at the very beginning.

     Now, what are some of the specifics of this relationship? Let me lay out some of the principles that we now understand about the etiology of autoimmune disease.

Unlike some diseases, autoimmune diseases do not generally have a simple, single cause. There are usually two major categories of factors that are involved in causing autoimmune diseases: genetics and environment. Virtually every autoimmune disease combines these two. Let me explain more of what I mean. First, genetics. Genetics is involved in the development of autoimmune disease, but autoimmune diseases are not typical genetic diseases. What is a typical genetic disease? Most of us have heard of sickle cell anemia, and that's a genetic disease. That's a disease in which the victims of the disease have a specific genetic mutation. If you inherit this mutation from one parent, you have sickle cell trait; and if you inherit it from both parents, you have sickle cell disease. We know what the gene is, and we even know a great deal of how that works; so we know the etiology of that disease.