Juvenile RA, usually referred to as juvenile idiopathic arthritis or JIA, is the most common rheumatologic disease among children. It is also one of the most common chronic illnesses affecting children. Preference for the term JIA reflects, in part, the fact that this disease is distinct from adult RA. JIA really covers a range of forms of chronic arthritis in children and includes more subtypes than the older term juvenile RA had covered.1
JIA affects approximately 300,000 children under the age of 18 years in the US. The incidence (new cases occurring every year) and prevalence (the total number of existing cases at a given time) of JIA varies by geography (from country to country), which suggests that genetic and/or environmental factors play a role in causing the disease. For instance, rates of JIA are highest among children of European ancestry and lowest in Japanese and Filipino children.1
What causes juvenile RA?
As with adult RA, the cause of this illness is thought to be a combination of genetic susceptibility and some environmental or other non-genetic factor that triggers the disease.1
The role of genetics in susceptibility for juvenile RA is supported by results from twin and family studies, where the prevalence of juvenile RA increases as the amount of shared genetic material increases. In other words, the risk of developing juvenile RA is higher in families where one member has the disease and the risk is higher still among monozygotic twins who share identical genetic material. The risk of one identical twin developing juvenile RA when his or her twin has the disease is 15 to 30 times higher compared with the risk for juvenile RA in the general population.1
Characteristics of juvenile RA
Juvenile RA or JIA is defined as inflammatory arthritis that affects a child less than 16 years of age that lasts at least 6 weeks and involves at least one joint. It is characterized by joint effusion (an increase in the amount of synovial fluid in the joint) and/or presence of a combination of symptoms including limitation in the range of motion, pain or tenderness associated with joint movement, and increased warmth in at least one joint.1
Subtypes of juvenile RA or JIA
Different subtypes of juvenile RA or JIA vary according to their typical age of onset and whether they tend to affect one gender more than another.1 These subtypes include:
- Systemic onset JIA: characterized by arthritis in at least 1 joint, preceded by fever lasting at least 2 weeks, accompanied by one or more symptoms, including rash, enlargement of the spleen and/or liver, or lymph node involvement.
- Oligo JIA: arthritis affecting 1-4 joints during first 6 months of disease. Can be further categorized as persistent, affecting 4 joints or less during disease course, or extended, affecting more than 4 joints after the first 6 months of disease.
- Polyarthritis (RF-negative): arthritis that affects at least 5 joints during first 6 months of disease, with rheumatoid factor (RF) testing negative.
- Polyarthritis (RF-positive): arthritis that affects at least 5 joints during first 6 months of disease, with RF testing positive.
- Psoriatic arthritis: arthritis and psoriasis, or arthritis with 2 or more of the following: (1) dactylitis (sausage digit or swelling of entire digit); (2) nail pitting; (3) family history (first degree relative) of psoriasis.
- Enthesitis-related arthritis: arthritis or enthesitis (inflammation of areas where tendons or ligaments insert into bone).
- Undifferentiated arthritis: arthritis that fulfills criteria in none of the above categories or more than one of the above categories.
Subtypes of juvenile RA or JIA
How is juvenile RA diagnosed?
Juvenile RA is a diagnosis of exclusion. This means that a doctor must exclude a number of other conditions before determining that a patient has juvenile RA or JIA. These include infections, trauma, reactive arthritis, malignancy, and connective tissue diseases, such as systemic lupus erythematosus (SLE).1
Conditions that must be excluded before diagnosing juvenile RA or JIA
- Bacterial sacroilitis
- Toxic synovitis
- Septic joint
- Viral infection (EBV, parvovirus)
- Lyme disease
- Behçet’s disease
- Kawasaki disease
- Mixed connective tissue disease
- Malignant bone tumors
- Osteoid osteoma
- Accidental injury
- Rheumatic fever
Treatment for juvenile RA or JIA typically involves a combination of drug therapy and other modalities, including physical and occupational therapy and psychosocial interventions. Early detection and treatment is crucial to prevent damage to joints and other structures and growth disturbance. Recent advances in treatment, including the advent of biologic therapies have improved the outlook for patients with JIA and, in many cases, can limit damage and allow patients to lead normal, active lives.1
Drug treatment for juvenile RA includes non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, and indomethacin, which are first-line treatments. Cox-2 inhibitors (such as celecoxib) may be used in patients who cannot tolerate NSAIDS due to gastrointestinal side effects. Corticosteroid injections given in the joint cavity may be used in patients with limited disease and may be helpful in cases of Oligo JIA. Oral or intravenous corticosteroid treatments are often useful for systemic symptoms, such as those that may occur with systemic onset JIA. Nonbiologic disease modifying anti-rheumatic drugs (DMARDs), including sulfasalazine, azathioprine, hydroxychloroquine, leflunomide, cyclosporin, and methotrexate, have been shown to prevent structural damage to joints and may be required in two-thirds of patients with JIA. Biologic agents, including TNF inhibitors (etanercept, infliximab, adalimumab) and biologic agents that target other immune system pathways (abatacept, anakinra, tocilizumab, canakinumab), can be very useful and have been shown to reduce damage and complications arising from JIA.1
Does juvenile RA persist into adulthood?
In about half of cases, children who develop juvenile RA or JIA will continue to experience similar disease activity during adulthood. For children whose disease continues into adulthood, there is the potential for significant disability, including joint deformity, abnormalities in growth, and eye problems such as scleritis or uveitis.1