Demystifying autoimmune diseases: triggers, symptoms, and types

Published March 2, 2024. Last updated February 12, 2026.

Your immune system has one job: to protect you. It’s designed to recognize what belongs in your body and what doesn’t. But sometimes that system gets confused. Instead of responding to viruses and bacteria, it begins targeting healthy cells, the very cells it’s meant to protect. This misdirection is what autoimmune disease looks like, and it affects millions of people.¹

What is an autoimmune disease? 

Autoimmune diseases are a group of chronic conditions in which the immune system mistakenly targets the body’s own healthy cells and tissues.

Typically, the immune system protects the body by responding to harmful threats, such as viruses and bacteria, while leaving healthy cells alone. In autoimmune disease, the immune system loses this ability and mistakenly attacks healthy cells and tissues. Over time, this ongoing immune response triggers chronic inflammation (swelling and irritation) that may cause tissue damage and a range of symptoms or other health conditions, depending on the condition.¹

What causes autoimmune diseases?

Researchers are still learning more about what causes autoimmune diseases. However, they do know these conditions aren’t contagious; you can’t “catch” them from someone else or pass them to others through contact.²

Instead, it’s thought that a combination of factors may trigger autoimmune disease or increase a person’s risk of developing one, including³

• Viral infections, such as Epstein-Barr virus and COVID-19
• Genetics and family history
• Exposure to chemicals or toxins
• Smoking or tobacco use
• Certain medications
• Your sex (autoimmune conditions are more common in women)

Having one or more factors doesn't mean you'll develop an autoimmune disease, but it may increase your risk. If you have questions about what this could mean for you, please talk with your doctor.

What are antibodies? How are they involved in autoimmune disease?

Antibodies are proteins made by certain white blood cells as part of the immune system. Autoimmune diseases involve changes in how the immune system behaves, and those changes can often be seen in blood tests. Antibodies are one type of marker that can show whether the immune system may be unusually active, highlight patterns linked to certain conditions, and offer clues about what may be going on.

Different types of antibodies can offer different clues about immune activity⁵:

• Antibodies (also known as immunoglobulins) recognize and bind to antigens, substances the immune system identifies as a threat. Antigens can be harmful bacteria, harmless particles, or in the case of autoimmunity, even the body’s own cells and tissues. Once bound, antibodies neutralize the threat or mark it for destruction by immune cells
• IgM, IgG, and IgA are 3 common types of antibodies that can add timing and context to immune activity. IgM appears earlier, while IgG may appear later and remain detectable longer. IgA can add insight into immune activity in specific areas of the body. There are other antibodies that doctors may evaluate, such as Immunoglobulin E (IgE). They are not as commonly used for routine health screenings. These other antibodies, like IgE, are more often used in specialized care (e.g. allergies)
• Autoantibodies are antibodies that mistakenly target the body’s own healthy cells and tissues. Their presence can suggest autoimmune activity and may help guide further evaluation when symptoms don’t fit a typical pattern
• Antinuclear antibodies are a type of autoantibody that specifically targets the nucleus of cells, where DNA is stored. Their presence can suggest autoimmune activity and support further evaluation 

What are the different types of autoimmune diseases?

There are over 100 known autoimmune diseases, and they can affect nearly any organ and can develop at any age.⁴ Some involve specific joints or tissues, while others affect multiple areas and are more widespread. Below are only a few types of autoimmune diseases and some areas of the body they may affect.¹⁻⁴,⁶⁻¹⁰

Can a person have more than one autoimmune disease?

Yes, some people are diagnosed with more than one autoimmune condition over time. This happens because autoimmune diseases can share underlying immune system patterns. When the immune system is already misdirected in one way, it may be more likely to do so again, sometimes affecting a different part of the body. But while having one autoimmune disease increases the risk of developing another, it doesn’t mean that it will happen.⁴,¹⁰

How can autoimmune disease affect a person’s daily life and overall health?

There are many types of autoimmune disease, and each can affect the body—and each person—differently. Autoimmune disease isn’t just a list of physical symptoms. It’s complex, involving patterns, unpredictability, flares, periods of remission, and ongoing day-to-day impact. Symptoms may be mild or severe, overlap, come and go, or affect more than one part of the body, making them hard to recognize or explain.

Depending on the condition and the area of the body affected, symptoms can be wide-ranging, such as¹⁻³

• Muscle aches, pains, or weakness
• Joint pain, stiffness, or swelling
• Inflammation
• Anemia
• Abdominal pain
• Bloating
• Constipation, diarrhea, or bloody stools
• Nausea or loss of appetite
• Weight gain or loss
• Skin rashes or sores
• Dry eyes, mouth, or skin
• Hair loss
• Headaches or migraines
• Dizziness
• Blurry vision
• Brain fog
• Memory issues
• Ongoing fatigue or low energy
• Sleep issues
• Anxiety or depression
• Fever
• Swollen lymph nodes
• Breathing troubles or Shortness of breath

How is rheumatoid arthritis different from other autoimmune diseases or forms of arthritis?

Rheumatoid arthritis is a long-term autoimmune disease in which the immune system mistakenly attacks the lining of the joints. This can cause painful inflammation, often in the wrists, hands, knees, or feet, but it can also affect organs such as the eyes, lungs, and heart. Without treatment, ongoing inflammation can permanently damage the joints, leading to chronic pain and mobility challenges.¹¹

Unlike some autoimmune diseases that mainly affect specific organs or parts of the body, rheumatoid arthritis can involve many joints at once and affect the whole body. It's also different from "regular arthritis" (osteoarthritis), which is caused by wear and tear on the joints over time, not an attack by the body's own immune system.

About 75% of people living with rheumatoid arthritis are women. And for many, symptoms typically begin between age 30 and 50.¹¹

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