By TRA Radiologist
Michael Chester, MD.
What is Juvenile Arthritis?
Juvenile idiopathic arthritis (JIA) is a group of diseases that cause arthritis before the age of 16 years. It can cause persistent joint pain, swelling and stiffness. For some children symptoms only last a few months but others have symptoms that last many years.
Juvenile idiopathic arthritis can affect one joint or many. The most common type affects four or fewer joints. There are also polyarticular types that involve more than four joints and a systemic type that is more serious and causes abnormalities such as fever, lymphadenopathy, organ dysfunction, and rash.
Symptoms
- Pain, which may or may not include joint pain. Instead of complaining of joint pain children may limp, especially in the morning or after a nap.
- Joint swelling is common but especially noticeable in the large joints such as the knee.
- Stiffness. Children may seem unsteady or have difficulty when they awake in the morning or after a nap.
- Systemic symptoms such as fever, swollen lymph nodes, and rash.
Causes
Juvenile idiopathic arthritis is an autoimmune disease in which the body attacks its own cells and tissues. The cause is not known but genetics and the environment are both thought to play a role. The prevalence of the disease is approximately 16-150 per 100,000 children.
Complications
- Eye inflammation which can result in cataracts, glaucoma, and blindness.
- Growth disruption. Bone growth and development can be disrupted by JIA. In addition, corticosteroids, which are used to treat JIA, can also inhibit growth. In advanced cases bones can fuse (ankylose) and disrupt growth.
- Permanent joint damage. Some cartilage damage can be repaired in children given the more vascular nature of their growing cartilage and cartilage caps (epiphyses). However, if the cartilage loss becomes greater than the body can repair then permanent cartilage loss ensues, leading to progressive joint space loss and in certain cases joint fusion.
Diagnosis
- JIA remains a clinical diagnosis with varied manifestations. Clinical exam, blood tests to detect inflammatory change, and imaging all play roles in diagnosing JIA.
Imaging
Imaging is important to diagnose and monitor the course of the disease. Radiography (x-ray) is often the initial imaging exam but is insensitive for early findings of JIA. However, radiography is necessary because it can exclude other causes of joint pain such as tumors or fractures. It can also detect advanced changes of arthritis such as erosions, joint space loss, and joint effusions. Contrast enhanced MRI is the most sensitive modality to detect early changes of JIA such as inflammation of the lining of joints (synovitis), joint effusions, and bone marrow edema which is a precursor to erosive change. Ultrasound (US) is also more sensitive than radiography for early changes of JIA and can detect synovitis, joint effusions, and tenosynovitis (inflammation of the tendon sheath). Both MRI and US can used to monitor treatment response and progression of JIA.
Treatment
Treatment of JIA focuses on anti-inflammatory medications which range from common over the counter nonsteroidal anti-inflammatory drugs (NSAIDS) to powerful biologic agents which suppress the immune system. These medications help decrease pain, improve function, and minimize joint damage.
Conclusion
Although JIA remains a clinical diagnosis, imaging is key in excluding other causes of joint pain and swelling, aids in diagnosis, monitors disease progression and treatment response, and evaluates for complications of JIA. Given the new powerful therapeutics the goal of JIA treatment is suppression of joint inflammation before the development of irreversible cartilage loss.
Sheybani, Elizabeth et al. Imaging of Juvenile Idiopathic Arthritis: A Multimodality Approach. Radiographics 2013; 33 (5): 1253-1273.
