Juvenile rheumatoid arthritis

Alternative names:

JRA; juvenile chronic polyarthritis; Still disease

Definition:

A chronic, inflammatory disease that may cause joint or connective tissue damage. The onset occurs before age 16.

Causes, incidence, and risk factors:

JRA is thought to belong to the collagen classes of disease (those diseases that involve connective tissue).

It is a complicated disease. The primary manifestation is arthritis, but the disease may involve other body systems such as the heart and lining around the heart (pericardium), lungs and lining around the lungs (pleura), eyes, and skin. Systemic arthritis affects 20% of those with juvenile arthritis and includes fever, rash, and enlarged spleen (splenomegaly) in addition to joint inflammation. JRA is generally divided into five broad groups depending on whether a large number of joints are involved or just a few, whether the rheumatoid factor (a blood test) is positive or negative, and whether there is eye involvement or not.

The five categories of JRA may be roughly broken down as follows:

• many involved joints and a positive rheumatoid factor
• many involved joints and a negative rheumatoid factor
• few involved joints and a positive antinuclear antibody
• few involved joints and a positive HLA B27 surface antigen
• systemic JRA (throughout the body)

The category determination is generally made by a specialist in rheumatology.

The onset of arthritis may be slow or extremely rapid. An early sign of slow onset may be stiffness on arising in the morning. The arthritis of JRA is characterized by swollen painful joints with pain on motion and sometimes to touch. The skin over the joints is generally not red but can be. The systemic form of JRA may first appear with high fevers, chills and a rash but without joint pain. In the systemic form, arthritis may develop months after the appearance of the fever.

The two forms of JRA where there are only a few joints involved often have associated eye disease. The most severe form of eye disease, chronic iridocyclitis of JRA, may lead to lead to visual problems or blindness. The milder form of JRA-associated eye disease is acute iridocyclitis, which generally heals without permanent damage.

The cause of juvenile rheumatoid arthritis is unknown. Growth may be affected during periods of active disease. Girls are affected more often than boys. The peak onset occurs between the ages of 2 to 5 years old and between 9 to 12 years old. Risk factors may be a family history of the disease and recent rubella infection or vaccine.