Juvenile idiopathic arthritis (JIA) is the name given to a group of conditions characterized by joint inflammation or arthritis, occurring first before the age of 16.
Juvenile idiopathic arthritis is an autoimmune group of diseases, caused by the production of autoantibodies or antibodies directed against the body’s own tissues rather than targeting foreign molecules or organisms. In this case, the antibodies bind with and injure the synovial membrane of the joints, leading to articular inflammation and injury.
There are seven types of juvenile idiopathic arthritis as follows:
Oligoarticular (pauci-articular) JIA - the most common form in the USA
Rheumatoid factor (RF)-positive polyarticular JIA
Rheumatoid factor-negative polyarticular JIA
. The criteria for classification include:
The number of joints affected
Symptoms and signs
JIA is estimated to occur in 4 to 16 of every 100 000 children. Both genetic and environmental factors play a role in its causation. Certain gene loci have been identified that are linked to a higher risk for JIA, and are also associated with specific types of JIA. This is presumably by causing excessive production or release of inflammatory mediators and augmenting normal inflammatory reactions around the joint. Other genes have also been studied in relation to the occurrence of JIA.
Infection and other events that provoke inflammation are also thought to be connected with the risk of developing JIA.
Most cases of JIA have no family history, but siblings of affected individuals do have a 12-fold risk of developing the condition.
Diagnosis and management
JIA in children may lack obvious symptoms or signs, even joint swelling is often absent. Laboratory tests as for rheumatoid factor are usually negative in children. Thus the diagnosis needs to be made on clinical grounds.
Common manifestations include:
Abnormal or limping gait
Complaints of limb stiffness on waking
Reduced use of one limb
Lowered level of activity
Constant or persistently recurring fever
Swelling of the joints
Inability to perform fine motor activities
The clinical features of this childhood condition are relatively non-specific, and therefore care is required to rule out other disorders such as systemic lupus erythematosus (‘lupus’), childhood malignancies or bone cancers before entertaining this diagnosis.
Uveitis or iridocyclitis are ocular manifestations of the condition, sometimes occurring without any signs or symptoms either in the body or in the eye.
A detailed physical examination is required to pick up associated findings such as hepatosplenomegaly. A nti-nuclear antibody (ANA), RF, HLA-B27 and a complete blood count with erythrocyte sedimentation rate (ESR) are tests that are often ordered. Joint fluid may sometimes be tapped. Imaging of the joint structure and of the eye may be required.
Treatment aims include controlling the inflammation, preventing further joint damage and keeping the joint and the person functional.
Non-steroidal anti-inflammatory drugs (NSAIDs) are the most commonly used first-line agents. If the patient is slow to improve with their use, a second category of drugs is added. These are called the Disease-Modifying Anti-Rheumatic Drugs (DMARDs). . Biologics also belong to this group, and include monoclonal antibodies against various components of the inflammatory reaction . Intra-articular steroid injections are used if only one joint is involved. Oral corticosteroid therapy is restricted in children because of the severe potential side-effects.
Exercise, an active lifestyle, and psychological support are also essential.
Reviewed by Catherine Shaffer, M.Sc. References
American College of Rheumatology, Juvenile Arthritis
NIHUS NationalLibraryof Medicine, JuvenileIdiopathic Arthritis
https://medlineplus.gov/ency/article/000451.htm Further Reading