iStock
WHEN A FRIEND’S college-age daughter came home from a gynecological appointment with the diagnosis of an “autoimmune disease,” my friend asked me to look into it. At first, I found the diagnosis, lichen sclerosus (symptoms include white spots, itching and pain), attributed to an “overactive immune system,” which sounded better than an autoimmune disease (AD). But when the condition was also traced to previous trauma or infection, it qualified as an AD.
In autoimmune diseases—the most common being Type 1 diabetes, rheumatoid arthritis and Lupus—the body’s immune system attacks normal, healthy tissue, causing inflammation and damaging or destroying the body’s tissue or organs. Often there is no obvious trigger, although infection and/or trauma appear to play a role because ADs often follow bacterial or viral infections. Multiple Sclerosis (MS) patients are twice as likely to have antibodies to the measles virus compared with those without MS.
ADs can produce effects ranging from severe to mild and barely noticeable: I discovered long after getting to know two friends that one has Hashimoto’s and the other Sjogrens syndrome (affecting the moisture-producing glands).
Women make up about 75% of those afflicted with autoimmune diseases, and ADs represent the fourth-largest cause of disability among women. Ratios of female to male sufferers range from 50:1 for Hashimoto’s syndrome (thyroid deficiency) to 9:1 for Lupus and 2:1 for MS. (Crohn’s disease is one that affects both sexes equally.)
Hormones are thought to play a role in the increased susceptibility of women to AD. Women demonstrate larger inflammatory responses in general compared to men. Also, AD symptoms can vary and intensify depending on estrogen levels; and having been pregnant increases risk for AD. Because estrogen appears to modulate immune activity, declining estrogen production with age can set off a chain reaction leading to increased inflammation.
An overactive immune system, on the other hand, blamed for conditions such as asthma and eczema, is reacting to normally harmless substances in the environment. Called allergens, these include dust, mold, pollen and certain foods.
What is shared by both abnormalities is the suspicion of a genetic component— a susceptibility or vulnerability that makes some people more likely to develop the conditions, often in response to a virus or something in the environment. The propensity can run in families: My friend’s other daughter has a gene strongly correlated with ankylosing spondylitis, a kind of arthritis that can cause inflammation of the spine, discovered when she had backaches during adolescence. In addition, people with one AD are more likely to be diagnosed with another.
Autoimmunity is present to some extent in everyone. According to one theory, low-level autoimmunity may help the body clear away unnecessary or used-up cells. Another role might be to create a rapid response in the early stages of infection, preparing the immune system to fight during the period before enough foreign antigens are present to stimulate a systemic immune reaction. Finally, LDL cholesterol particles that lodge in the lining of an artery can over time trigger low-level inflammation, which eventually causes blood clots that block the artery.
Inflammation is part of the body’s healthy response to outside invaders like infections but at a persistent, low level may contribute to everything from depression to Alzheimer’s disease. Treatment for autoimmune diseases requires reducing immune activity without damping it down too much, which would leave the body unprotected. Until recently, AD treatments—steroids, chemotherapy and immunosuppressants—have been blunt instruments, but newer remedies in the pipeline target the specific malfunctioning parts of the immune system: for example, monoclonal antibodies used to treat rheumatoid arthritis.
ADs are rare in geographic areas where infectious diseases are endemic, possibly because infectious agents such as parasites lower their victims’ immune response in the process of reproducing and spreading infection. The “hygiene hypothesis,” though unproven, posits that the human immune system is designed to respond to certain levels of infection and over-reacts when that level isn’t reached. Another possible explanation is the weakening of the gut microbiome in individuals who take antibiotics or in the presence of absence of certain foods, such as gluten.
Conversely, certain chemical agents and drugs are associated with increased risk of ADs: Cigarette smoking is a major risk factor for the incidence and severity of rheumatoid arthritis.
The NIH estimates that 23.4 million Americans, or as much as 8% of the U.S. population, suffer from autoimmune diseases; while the American Autoimmune and Related Diseases Association puts the number as high as 50 million and counts many more ADs than the NIH. By all counts, the U.S. appears to have the highest prevalence of ADs in the world.
—Mary Carpenter