We take for granted that our immune system is always looking out for us.

But in the case of rheumatoid arthritis (RA)—an autoimmune condition that affects over 1 million adults in the US—the body's defense system turns on us.

Usually, our immune system is busy fighting infectious organisms and other invaders, but with RA, the immune system gets confused and attacks healthy cells that line our joints, causing inflammation.

The resulting inflammation in the joint leads to swelling, pain, and stiffness. If left untreated, RA can lead to permanent joint damage and diminished quality of life.

To better understand RA, we spoke with rheumatologist Dr. Lindsy Forbess.

Dr. Forbess: RA tends to affect smaller joints first, particularly in the hands and feet. As the disease progresses, symptoms like swelling and stiffness often spread to the wrists, knees, ankles, elbows, hips, and shoulders.

The joint swelling is usually symmetrical, meaning if one hand or wrist is affected, the other one is too.

Other warning signs are joint stiffness that lasts at least 30 minutes and is worse in the mornings and after inactivity.

RA is referred to as a systemic disease—one that affects the entire body—because it can also affect the cardiovascular or respiratory systems, among others. For this reason, fatigue, generalized weakness, and unexplained weight loss could all point to RA.

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Dr. Forbess: A distinguishing feature between RA and osteoarthritis (OA)—the common arthritis that often comes with age—is that RA joint stiffness is usually worse with inactivity (like first thing in the morning), typically lasts more than 30 minutes, and improves with activity, whereas OA stiffness (if it occurs in the morning) is usually less than 30 minutes and returns at the end of the day or after use of the joint.

Dr. Forbess: We know that women are 2-3 times more likely to develop RA than men.

The condition can occur at any age, but RA commonly begins between the ages of 40 and 60.

If a family member, particularly a first-degree relative such as a parent, sibling, or child has RA there is an increased risk of developing the disease. However, the majority of people with RA have no family history of the disease.

Cigarette smoking increases the risk of developing RA, particularly if there is an underlying genetic predisposition to developing the disease. Smoking also appears to be associated with greater disease severity.

People who are overweight or obese also tend to be at a somewhat higher risk of developing RA.

Also, some environmental exposures, such as to silica or asbestos, may increase the risk of developing RA.

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Dr. Forbess: Those who have persistent joint pain and swelling for more than 6 weeks should have an evaluation for RA.

A physician will do a thorough history and physical exam and may recommend certain tests—including blood tests and imaging—to distinguish RA from other types of arthritis.

Dr. Forbess: It is essential to diagnose RA as early as possible because early diagnosis and treatment can slow the progression of the disease and prevent joint damage and disability.

If inflammation goes unchecked, it can damage cartilage, the synovium (tissue that covers or lines the joint), and even the bones themselves.

The goal is to treat RA early and aggressively so that all patients with RA can reach and remain in remission.

If there is any doubt about whether or not you have RA, get evaluated because early detection and treatment lead to better outcomes for each individual.