ST. LOUIS - Joint pain is a very common complaint made by children. The most frequent reasons for it include simple things like falling down and scraping a knee or twisting an ankle. But sometimes a child’s joints become swollen and stay that way for weeks or even months for no obvious reason. When swelling or extra fluid has been present in a joint for at least six weeks, a child can be classified as having chronic arthritis. And, if no other cause for the arthritis can be found, the child may be diagnosed with juvenile idiopathic arthritis (JIA).
Although JIA has been known by other names in the past, including juvenile rheumatoid arthritis, it has always referred to a category of diseases where a child’s joints are assaulted by what’s normally supposed to defend them – the immune system. Disorders in which someone is attacked by their own immune system are known as autoimmune diseases and are often managed by a rheumatologist. While we don’t completely understand the reasons autoimmune diseases develop, we believe that a piece of the puzzle involves certain genes (specific sections of DNA inherited from parents) that inappropriately allow the immune system to become “overactive” and damage parts of the body.
Many autoimmune diseases are quite rare in children but JIA is relatively common. In fact, it’s diagnosed in nearly one of every 1,000 children in the U.S. each year. Of the seven subtypes of JIA, the most common is oligoarticular. This accounts for 50 – 80 percent of JIA and occurs three times more often in girls than boys. The peak age of onset is around 2 years.
Children with oligoarticular JIA have four or fewer involved joints. Although almost any joint can be affected with this type of JIA, close to 90 percent of patients have their knee joint affected. Children with this disease are also at risk for developing uveitis (inflammation in the eyes).
In contrast to most other joint problems, oligoarticular JIA is often painless so children will continue to play without much complaint. In fact, if they have prominent pain, other causes of arthritis like injury or infection should be considered. A far more typical symptom in oligoarticular JIA is joint stiffness. Parents often comment that their child is “walking like an old person” after waking up in the morning or following a nap. However, after the joint warms up, the stiff walk and limp generally improves. This observation can be extremely useful for a physician when they are trying to sort out what might be going on with a child with joint complaints. Although there’s no test to diagnose JIA, blood tests and imaging studies (x-rays, CTs or MRIs) may be obtained during the evaluation.
Once a JIA diagnosis has been made, it’s important to start medications to calm the immune system and reduce inflammation in affected joints. As recently as 15 years ago, therapies for JIA were limited and sometimes had significant side effects. Fortunately, there has been major progress in our understanding and treatment of JIA. Perhaps the biggest leap forward has been the development of medications that more specifically target the overactive parts of the immune system yet produce fewer side effects. And, although we’re not yet able to cure JIA, we now have a great chance of controlling the disease and allowing most children to lead active, largely normal lives with these new medications.