Baby Elli is now a bit older than Addisen was when she was diagnosed with the disease. “Elli’s fine so far, but any time she complains about a joint, falls or says ‘owie’ that’s the first thing that comes to my mind,” admits Staci. “I think because we’ve been through it once, we tend to think the worst right off the bat.”

Marta Moroldo of the University of Cincinnati found that siblings with JIA tend to develop the disease around the same age. For example, in a family with a 10- and 6-year-old, the 10-year-old got JIA when he was 5, and so did the 6-year-old. Moroldo also found that siblings are more likely to have the same subtype of arthritis.

Will my kids inherit JIA?

When Addisen Ogden is grown up, will she have to worry about having kids with JIA? Researchers don't yet know.

“At this point we know of more sibling pairs than parent-child pairs with JIA,” says Dr. Prahalad.

Constructing accurate family histories for studies of parents of kids with JIA is sometimes difficult since pediatric rheumatology as a specialty is very young. A formal classification system for juvenile arthritis was proposed in the U.S. only in the 1970s.

In the meantime, the pace of genetic research into the causes of arthritis continues to accelerate, as does the development of new drugs to treat JIA.

“As scared as parents are of JIA, if properly diagnosed and managed, children have really good quality of life and really good outcome these days,” says Dr. Prahalad.