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’s supposed to fight off invaders to keep us healthy. But sometimes it becomes a traitor and attacks our own cells and tissues.

So-called autoimmune diseases can affect almost any part of the body – and affect tens of millions of people. Although more common in women, these diseases can strike anyone, adults or children, and they are on the rise.

New research raises the prospect of treatments that could do more than relieve symptoms. Dozens of clinical trials are testing ways to reprogram a haywire immune system, with some promising early success against lupus, myositis and some other diseases. Other researchers are looking for ways to at least delay the onset of autoimmune diseases, boosted by a drug that can buy time before people show symptoms of type 1 diabetes.

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

Here are a few things to know.

These are chronic illnesses that can range from mild to life-threatening, there are over 100 with different names depending on how and where they cause damage. Rheumatoid arthritis and psoriatic arthritis attack the joints. Sjögren’s disease is known for dry eyes and mouth. Myositis and myasthenia gravis weaken muscles in different ways, the latter by attacking the way nerves signal them. Lupus has a wide variety of symptoms, including a butterfly-shaped rash, joint and muscle pain, fever, and damage to the kidneys, lungs, and heart.

They are also finicky: even patients who have been well for long periods can suddenly have a “flare” for no apparent reason.

Many start with vague symptoms that come and go or mimic other illnesses. Many also have overlapping symptoms – rheumatoid arthritis and Sjögren’s disease can also damage major organs, for example.

Diagnosis may require 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 multiple doctors to piece together the clues. Efforts are being made to improve: The National MS Society is informing doctors about recently updated guidelines to streamline the diagnosis of multiple sclerosis.

The human immune system is a complex army composed of sentinels to detect threats such as germs or cancer cells, various soldiers to attack them, and peacemakers to calm the situation once the danger has passed. The main thing is that it can distinguish what is foreign from what is “you”, which scientists call tolerance.

Sometimes confused immune cells or antibodies escape, or peacemakers fail to calm things down after a battle. If the system fails to detect and resolve the problem, autoimmune diseases gradually develop.

Most autoimmune diseases, especially in adults, are not caused by a specific genetic abnormality. Instead, a variety of genes that affect immune functions can make people susceptible. Scientists say it then takes an “environmental” trigger, such as infection, smoking or pollutants, to trigger the disease. For example, the Epstein-Barr virus is linked to MS.

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

Women represent approximately 4 out of 5 autoimmune patients, many of whom are young. Hormones are thought to play a role. But also, women have two X chromosomes while men have one X and one Y. Some research suggests that an abnormality in the way female cells turn off this extra X may increase women’s vulnerability.

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

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

The global market for autoimmune disease treatments is worth $100 billion a year, according to investment research firm Morningstar. That’s not counting visits to the doctor and hours lost at work. Treatment is lifelong and, although usually covered by insurance, can be expensive.

Not long ago, there wasn’t much on offer for many autoimmune diseases beyond high-dose steroids and large-scale immunosuppressive medications, with side effects that include the risk of infections and cancer. Today, some newer options target specific molecules, which puts a little less strain on the immune system. But for many autoimmune diseases, treatment relies on trial and error, with little to guide patients’ decisions.

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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. The AP is solely responsible for all content.