There are more than 100 autoimmune diseases, and they mostly strike women. Here’s what to know

Our immune system has a dark side: it must fight off invaders to keep us healthy. But sometimes he becomes a traitor and attacks our own cells and tissues.

What are called autoimmune diseases can affect virtually every part of the body—and affect tens of millions of people. Bye most common in womenthese diseases can affect anyone, adults or children, and their numbers are increasing.

New research is opening up the prospect of treatments that could do more than just reduce symptoms. Dozens of clinical trials are testing ways to reprogram an out-of-control immune system, and there have been some promising early successes. against lupusmyositis and some other diseases. Other researchers are looking for ways to at least delay the development of autoimmune diseases stimulated by the drug, which could buy some time before people show symptoms of type 1 diabetes.

“This is probably the most exciting time we've seen in autoimmunity,” said Dr. Amit Saxena, a rheumatologist at NYU Langone Health.

Here are some things to know.

What are autoimmune diseases?

These are chronic diseases that can range from mild to life-threatening, and there are more than 100 of them with different names depending on how and where they cause harm. Rheumatoid arthritis and psoriatic arthritis affect the joints. Sjogren's disease is known for dry eyes and mouth. Myositis and myasthenia gravis weaken muscles in different ways, with the latter affecting the way nerves send signals to them. Lupus has a wide range of symptoms, including a butterfly-shaped rash on the face, joint and muscle pain, fever, and damage to the kidneys, lungs, and heart.

They are also capricious: even patients who have been feeling well for a long time can suddenly experience a “flare-up” for no apparent reason.

Why are autoimmune diseases so difficult to diagnose?

Many begin with vague symptoms that come and go or mimic other diseases. Many also have overlapping symptoms: for example, rheumatoid arthritis and Sjögren's disease can damage important organs.

Diagnosis may involve several tests, including blood tests to detect antibodies that mistakenly attach to healthy tissue. It usually focuses on symptoms and involves ruling out other causes. Depending on the disease, it can take years and visits to multiple doctors before anyone can piece together the clues. Improvement efforts are underway: The National Multiple Sclerosis Society is educating physicians about recently updated guidelines to make diagnosing multiple sclerosis easier.

How the immune system fails

The human immune system is a complex army, with sentinels who detect threats such as germs or cancer cells, many soldiers who attack them, and peacekeepers who calm the situation when the danger has passed. The key is that he can distinguish what is foreign from what is “you,” what scientists call tolerance.

Sometimes confused immune cells or antibodies slip through, or peacekeepers can't calm down after a fight. If the system fails to detect and correct the problem, autoimmune diseases gradually develop.

Autoimmune diseases are often caused by a trigger

Most autoimmune diseases, especially in adults, are not caused by a specific gene defect. Instead, different genes that affect immune function may make people susceptible. Scientists say the disease requires some kind of “environmental” trigger, such as infection, smoking or pollutants. For example, Epstein-Barr virus is associated with multiple sclerosis.

Scientists have focused on the earliest molecular triggers. For example, white blood cells called neutrophils are the first to respond to signs of infection or injury, but abnormally overactive cells are thought to play a key role in lupus, rheumatoid arthritis and other diseases.

Women are at greatest risk for autoimmune diseases

Women make up about 4 out of 5 autoimmune patients, many of them young. Hormones are thought to play a role. But also, women have two X chromosomes, and men have one X and one Y. Some research suggests that the anomaly in the way women's cells switch off is that the extra X chromosome may increase women's vulnerability.

But men suffer from autoimmune diseases. One particularly severe one, called VEXAS syndrome, was only discovered in 2020. It primarily affects men over 50 and can cause blood clots, shortness of breath and night sweats in addition to typical autoimmune symptoms.

Certain populations are also at higher risk. For example, lupus is more common in black and Hispanic women. Northern Europeans have a higher risk of multiple sclerosis than other groups.

Treating autoimmune diseases is difficult

The global market for treating autoimmune diseases is worth $100 billion annually, according to investment research firm Morningstar. This doesn't include doctor visits and things like lost time at work. Treatment lasts a lifetime and, although usually covered by insurance, can be expensive.

Not long ago, there was little available to treat many autoimmune diseases other than high doses of steroids and a wide range of immunosuppressive drugs, with side effects that included the risk of infections and cancer. Today, some new variants target specific molecules, weakening immunity to a slightly lesser extent. But for many autoimmune diseases, treatment is trial and error, with little impact on patient decision-making.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education and the Robert Wood Johnson Foundation. AP is solely responsible for all content.