Powerful medicines can slow joint damage for RA sufferers

Q: I have rheumatoid arthritis. Can you explain what is happening in my body to cause such uncomfortable symptoms?

A: Rheumatoid arthritis (RA) is a chronic (long-term) disease. It causes painful and sometimes disabling inflammation of the joints. RA can also affect other tissues in the body, such as the skin, eyes, lungs and blood vessels.

RA is an autoimmune disease. That means the immune system mistakenly identifies normal, healthy cells as dangerous and attempts to destroy them. Why does this happen? Do the normal, healthy cells somehow "look" foreign to the immune system? Or is there something in the normal cells, like a virus that hasn't yet been discovered, that attracts the attention of the immune system? There are a lot of scientists trying to figure that out.

In RA, the immune system targets synovial joints, the movable joints found in the shoulders, elbows, wrists, fingers, hips, knees, ankles and toes. In these joints, a protective layer of cartilage covers the ends of the bones where they meet. The joints take their name from the synovium, a membrane that lines the joint.

The synovium produces synovial fluid, a thick, sticky, yellowish liquid. It lubricates the joint and minimizes friction. It also forms a seal that allows neighboring bones to slide freely against each other without pulling apart.

RA occurs when the immune system mistakenly attacks the synovium. The attacking cells release inflammatory chemicals that increase blood flow to the site. They direct an army of white blood cells, germ-fighters and other substances into the invaded tissue. White blood cells produce intense inflammation.

In response to the inflammation, synovial cells also begin to multiply. This causes the normally smooth synovium to form a rough, grainy tissue called pannus. The pannus grows into the previously empty space in the joint. In addition, synovial cells and other cells produce chemicals that eat away at the cartilage in the joint.

Together, the pannus and the inflammatory chemicals badly damage the joint. If the tendons become inflamed, they may shorten and prevent the joint from bending. If the tendons rupture, the joint may become loose or floppy. (I've put an illustration of this process on my website, AskDoctorK.com.)

In a normal immune system response, inflammation subsides when the threat is removed. But in RA, the immune response is not normal; it continues indefinitely. This prolonged inflammation can be devastating. The result is swelling, redness, heat and pain in the joints. Ultimately, the joints can be so badly damaged that they become deformed. People with RA can have great difficulty walking, bending, lifting or using their hands.

As RA progresses, it can limit a person's ability to carry out normal daily activities such as dressing, bathing and walking. However, with medications, good self-care and, if necessary, surgery, most people with RA can avoid disability. In the past decade, research has led to powerful new medicines that prevent the slow destruction of the joints in many people with RA. I hope your doctor has prescribed one of these medicines for you.

• Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.