Juvenile idiopathic arthritis (JIA)

Juvenile idiopathic arthritis is the most common form of chronic arthritis in childhood, in which the immune system is understood to drive persistent joint inflammation in a child under 16, with several subtypes that behave differently and a cause that is not fully understood.

A systematic review found incidence estimates ranging from roughly 2 to 23 per 100,000 children per year and prevalence ranging just as widely, from under 4 to as high as 400 per 100,000, a spread researchers attribute to differences in study methods and classification systems across regions. More recent UK population data found an incidence around 5.6 per 100,000 and prevalence around 43.5 per 100,000, and research consistently finds JIA affects girls more often than boys. Depending on the subtype, some children also develop silent eye inflammation that requires ongoing monitoring.

Common signs

Joint pain, swelling, warmth, and stiffness, often worse in the morning or after rest, sometimes with limping or a reluctance to use a limb. Depending on the subtype, there may also be fever, rash, or eye inflammation (uveitis), which can be silent and is watched closely.

This is a plain-language summary for orientation, not a diagnosis. Mechanisms are described as current understanding, not settled fact. Work with your own clinician for your care.