Subtypes of Juvenile Idiopathic Arthritis

Years ago, there were three types of juvenile rheumatoid arthritis that were recognized. In the United States, juvenile rheumatoid arthritis was also referred to as JRA, or juvenile arthritis. The European League Against Rheumatism referred to JRA as juvenile chronic arthritis. The three types of JRA were pauciarticular, polyarticular, and systemic.

Later, the International League of Associations for Rheumatology (ILAR) divided juvenile arthritis into more subtypes. This was done primarily for research purposes and will continue to evolve as more is learned about genetics and the pathogenesis of juvenile idiopathic arthritis (JIA).

Children with polyarthritis-rheumatoid factor negative have arthritis affecting five or more joints in the first six months of disease. Rheumatoid factor tests are negative. This type affects 10-30% of children with JIA.

Children with polyarthritis-rheumatoid factor positive have arthritis affecting five or more joints in the first six months of disease. Two tests for rheumatoid factor, taken three months apart, are positive. This type affects 5-10% of children with JIA.

Children with oligoarthritis (affecting 30-60% of children with JIA) have arthritis affecting one to four joints within the first six months of disease. More than four joints may be involved after the first six months.

If the child has four or fewer joints affected throughout the course of the disease, it is called persistent oligoarthritis. If the child has more than four joints affected after the first six months, it is called extended oligoarthritis.

Children with systemic arthritis have arthritis symptoms, with fever lasting two weeks or more, spiking for three days or more, along with one of the following symptoms:

• Enlargement of lymph nodes
• Enlargement of liver or spleen (hepatomegaly or splenomegaly)
• Inflammation of the lining of the heart or lungs (pericarditis or pleuritis)
• Rash (non-itchy) of variable duration that may move to different parts of the body

Systemic arthritis affects 10% of children with JIA.

Children classified with the psoriatic arthritis subtype have both arthritis and psoriasis, or they are affected by arthritis and two of the following symptoms:

• Dactylitis (sausage fingers or toes)
• Nail pitting/splitting
• A first-degree relative with psoriasis

Psoriatic arthritis affects 2-15% of children with JIA.

Children with the enthesitis-related arthritis subtype have arthritis and inflammation at an entheses site (where a ligament, tendon, or joint capsule attach to bone) or have either arthritis or enthesitis along with two or more of the following:

• Inflammation of sacroiliac joints or pain and stiffness in the lumbosacral region
• Positive test for HLA-B27
• Arthritis onset in males older than 6 years of age
• First-degree relative with ankylosing spondylitis, enthesitis-related arthritis, inflammation of sacroiliac joint with inflammatory bowel disease, or acute eye inflammation (acute anterior uveitis).

This type of arthritis affects 20% of children with JIA.

This category pertains to children with arthritis symptoms who do not fit any of the other six categories—or they meet the criteria of two or more categories.

Ideally, it is best to consult with a pediatric rheumatologist to diagnose the disease and determine the subtype of juvenile idiopathic arthritis. Proper treatment depends on an accurate diagnosis. But, there is a shortage of pediatric rheumatologists. In fact, some states have none.