Researchers found that nearly half of the girls in the study who were ANA positive and between the ages of 1 and 2 at the onset of JIA went on to develop uveitis at some point in their lives. Their risk was about three times, or 300 percent, higher than any other group in the study.

But that risk decreased with each year of age, dropping to just a 10 percent chance of getting uveitis if a girl was diagnosed by age 7 or later. Boys did not have the same risk connected to age and ANA in their blood.

Another significant finding of the study was that with only a couple of exceptions, the specific kind of arthritis a child had, called their subtype, didn’t seem to influence the risk of developing uveitis.

Previously, experts had believed that subtype had a lot to do with whether or not kids would go on to develop the eye condition. Kids with oligoarthritis, for example, in which four or fewer joints are affected during the first six months, were previously thought to be in greatest danger.

Not so, researchers say.

“Now we were faced with the fact that in our cohort the subtype of JIA did not influence the risk of getting uveitis, but the major factors were the age at diagnosis of JIA and sex,” Dr. Saurenmann says. 

“Girls had a higher risk the younger they were at the diagnosis,” she continues. “The age association in girls was so strong that the risk of getting uveitis was even significantly higher in girls who were 1 year old at diagnosis of JIA than in 2-year-olds.”

Researchers say age is likely to be a factor because younger immune systems that haven’t fully matured may be more susceptible to autoimmune diseases.

But they don’t yet know why there are differences between boys and girls.

“As a rule women tend to be more affected by autoimmune diseases than men and it has therefore been discussed whether hormonal factors may play a role. However, in young children sex hormones are not produced to a significant amount,” Dr. Saurenmann says.

Edward Sills, MD, chief of pediatric rheumatology at Johns Hopkins Children's Center in Baltimore, Md., weighed in on the significance of the study.

"I am familiar with and applaud the study. It emphasizes important points,” Dr. Sills says. But he also cautions that kids who fall outside of these apparent high-risk categories, those who are older, male or who may be ANA negative, aren’t off the hook when it comes to eye screening.

Dr. Sills says that for now, it’s clear what parents should do. “The single most important step is for parents to have the child seen on a regular basis, at least twice a year or more frequently in the higher risk groups, by an ophthalmologist, not an optometrist, for slit lamp exams (lighted microscopic views of the eye) of the uveal tract,” he says. “Early diagnosis, which slit lamp surveillance provides, will minimize or prevent any adverse effects of uveitis and, likely, maintain normal vision."

Dr. Saurenmann agrees. “The earlier the diagnosis of uveitis is made and effective treatment begun, the fewer the complications and the better the long-term outcome of uveitis,” she says.