Although this girl’s symptoms strongly resemble RA, a pediatric rheumatologist will most likely diagnose her with a form of JA known as RF-positive polyarthritis. “On the other hand, when a patient develops arthritis at age 20, she’ll see an adult rheumatologist and get diagnosed with RA,” says Dr. Beukelman. “Biologically speaking, once children go through puberty, they’re more or less adults. But as far as we can tell, these two patients really have the same disease.”

Beukelman stresses that the vast majority of children diagnosed with JA do not have RA, nor do they have elevated RF antibodies.

A Disease in Transition

Adults with RA and JA both appear to have an increased risk for heart disease, as well as lymphoma and related forms of cancer. However, adults with JA can develop associated health issues that are uncommon in people with RA. As mentioned earlier, an eye condition called uveitis that’s virtually nonexistent in adults with RA can afflict some people with JA; past research indicates that about one in five patients with this eye condition will eventually develop cataracts, glaucoma, or partial blindness. What’s more, the combination of chronic inflammation and treatment with corticosteroids in youth can stunt bone growth; past studies have shown that about half of adults who were diagnosed with systemic arthritis as children are significantly shorter than their peers. People with JA tend to have fragile bones, too, probably due to a combination of the disease, the use of corticosteroids, and lack of exercise. A 1999 study found that 7 percent of young adults with JA (average age: 32) already had osteoporosis, which usually doesn’t emerge until midlife.

Disability is common among adults with JA today. “We have patients who are anywhere from 30 to 60 years old who have many, many damaged joints,” says rheumatologist Peter Nigrovic, MD, director of the Center for Adults with Pediatric Rheumatic Illness (CAPRI) at Boston’s Brigham and Women’s Hospital. That can affect a patient’s personal life: In the past, studies have revealed that adults with JA are less likely to marry and have children, and often struggle to find jobs. But that may be changing. “This is all data from older studies, when these patients were very commonly deformed,” says Dr. Nigrovic. “That’s just not the case very much anymore.”

What’s changed? JA has important similarity with RA: Both conditions respond well to disease-modifying anti-rheumatic drugs (DMARDs) that have become available in recent years, including methotrexate and the various biologic agents, such as the tumor necrosis factor (TNF) inhibitors etanercept (Enbrel), adalimumab (Humira), and others.

These medications have brightened the long-term outlook for children with JA, to say the least. When Taylor began treating children with arthritis 32 years ago it wasn’t unusual for some boys and girls to end up in wheelchairs. That’s almost unheard of today. “Studies show that the majority of kids who receive adequate medical therapy—70 to 90 percent —have satisfying outcomes and no disability,” says Taylor.

However, while treatment plans are similar for adults with both diseases, at least one form of JA seems to respond best to a medication that’s infrequently used to treat RA. A Dutch study published online in Annals of the Rheumatic Diseases last June found that children with systemic JA whose arthritis wasn’t well controlled with etanercept improved more if they took anakinra (Kineret) instead of adding another TNF inhibitor. Taylor explains that while the inflammation causing RA seems to be driven largely by TNF, systemic arthritis is probably triggered by another class of cytokines known as interleukins, which anakinra stifles. Earlier studies found that another drug that blocks interleukins, tocilizumab (Actemra), is effective for JA, too.

Whether taking DMARDs from a young age for many years will cause ill effects in adulthood is still unclear. “We don’t have any data that there’s a problem there,” says Dr. Nigrovic. “We just don’t know.” As the first generation of patients with JA who have access to these new and greatly improved medications grows up, doctors will undoubtedly learn more.