Autoimmune disease: Definition and examples

Our immune systems are versatile, armed with an array of weapons that can defend against all sorts of pathogens. But in some people, this powerful arsenal of immune cells and proteins occasionally engage in friendly fire by attacking healthy cells, tissues and organs. This self-inflicted assault is referred to as autoimmunity, and it plays a role in more than 100 diseases ranging from type I diabetes to rheumatoid arthritis, according to the National Institutes of Health (NIH).

Millions of people are affected by autoimmune diseases — an estimated 5% to 9% of the U.S. population has an autoimmune condition. And although there are many treatments on the market and in development that are designed to manage the often debilitating symptoms, autoimmune diseases remain incurable.

The prevalence of autoimmune diseases appears to be growing worldwide, although it is unclear why. Lifestyle factors, such as changes in diet, alongside advances in diagnostics and a better clinical understanding of these diseases, have likely contributed to the rise in numbers, said Emily Edwards, a researcher in the department of immunology and pathology at Monash University in Australia.

What causes autoimmune diseases?

Autoimmune diseases, like many other conditions, likely result from the interplay between genetic and environmental factors but their exact etiology is unclear and varies among disorders.

Still, people with a family history of autoimmune diseases are more likely to develop them — for example, multiple sclerosis runs in families. Some environmental factors such as pollutants, certain medications, viral infections and diet are also implicated in the manifestation of autoimmune diseases, according to Johns Hopkins Medicine.

Overall, women are twice as likely as men to suffer from autoimmune diseases — and the disorders typically emerge during periods of extensive stress, such as pregnancy, reported a 2020 review paper in the journal Cureus. Some autoimmune conditions are more common in certain races and ethnic backgrounds — for instance, lupus is most severe in African-American and Hispanic people, reports the U.S. Department of Health and Human Services (HHS).

Symptoms of autoimmune diseases

Although each disease has specific features, many share hallmark symptoms, such as fatigue, dizziness and low-grade fever. But the classic sign of an autoimmune disease is inflammation, which can cause redness, heat, pain and swelling, according to the NIH.

For many autoimmune diseases, symptoms come and go, or can be mild sometimes and severe at others.

Treatment for autoimmune diseases

There are a multitude of medicines used to treat autoimmune diseases, but what patients are prescribed is determined by the disorder, its severity and the symptoms the patient is experiencing. 

The medicines used could range from mild over-the-counter painkillers to drugs designed to replace vital substances the body can no longer make, such as insulin for diabetics.

Then there are biologic therapies that are designed to target components of the dysregulated immune response which can suppress the immune system, as well as drugs designed to control the overactive immune system by dampening its activity. 

Using these different types of immunosuppressants is fraught with complications because then the immune system is also potentially prevented from mounting a robust response to infections, Edwards said.

Related: Immunodeficiency: Definition and examples

So, doctors must carefully administer immunosuppressants to try and balance that risk, she said. "They're not the most effective drugs in the world, and what we're trying to do now is find … more targeted therapies that will be more effective."

Overall, the medicines we have are designed to tamp down the overactive immune response and the consequences of that overreaction — they don't really address the reason behind the immune system's malfunctioning, she explained.

"There's a need to identify what the underlying issues are … there's an incomplete understanding at this present moment about what exactly they are," she said. "Once we can do that, that gives us the opportunity to be able to correct those."

Autoimmune diseases and vaccines

Generally, people with autoimmune conditions are advised to get vaccinated, just as healthy people are. However, if they are on immunosuppressants that dial back the impact of the immune system, that might lead to a less than an optimum response to vaccines, including those against COVID-19, Edwards said.

Although there is little scientific consensus on what level of antibodies and other tools in the immune system's armament confer protective immunity against the virus that causes COVID-19, some countries have announced plans to administer third vaccine shots for their populations, including people with compromised immune systems.

Related: US to recommend COVID-19 booster shots 8 months post-vaccination

"They might need the extra dose to take them up to a level of a normal individual … in order to give them the protection they require against the virus," Edwards said.

Millions of people suffer from autoimmune diseases — estimates suggest that about 24 million in the U.S. alone live with these disorders. In a lot of cases, these look like invisible diseases, but patients are in constant peril because immunosuppressants make them far more susceptible to all kinds of infections and reduce their capacity to reap the full benefits of vaccines, she added.

"It's even more of a reason why the general population should be vaccinated," Edwards said, " in order to protect these people [with autoimmune diseases] because it's hard enough for them as it is, without having to deal with the worry of catching viruses."

Additional resources

• Learn more about why women tend to get more autoimmune diseases versus men in this explainer published by The Conversation. 
• Read more about how effective vaccines are in people with compromised immune systems in this explainer by the American Society for Microbiology. 

This article is for informational purposes only, and is not meant to offer medical advice.