Growth abnormalities. These include unequal leg lengths, an
imbalance in growth of the jaw, and temporary delay in breast
Joint damage. This is common in the polyarticular form of
JIA and can occur early. About 30 to 50 out of 100 children with JIA may have some level of
disability that continues into adulthood.2 Long-term problems can be mild and have little effect on daily activities.
Some children with polyarthritis get arthritis in the
neck that can cause the neck bones to fuse together.