Juvenile idiopathic arthritis (JIA) is the most common cause of paediatric anterior uveitis and is more likely in females. As mentioned in our classification of uveitis notes, this means that the inflammation affects the iris +/- pars plicata (a highly vascular layer of the ciliary body). Patients present with arthritis but ophthalmic symptoms occur in certain subtypes. These symptoms can cause decreased visual acuity and may progress to blindness if untreated or in treatment-resistant cases.
The cause of JIA is not well-established but individuals can sometimes be genetically predisposed depending on HLA subtyping. Those with the predisposition are then subjected to unknown environmental triggers that cause the immune-mediated arthritis. It has a prevalence of 1:1000, with slightly more likelihood in females than males.
Note that often anterior uveitis is associated with HLA-B27 however this is not the case in JIA. Instead, JIA is associated with HLADRB1 or HLADRB.
<aside> 💡 JIA is defined as an arthritis of unknown aetiology lasting 6 or more weeks in patients younger than 16 years old.
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This is then further classified according to the International League of Associations for Rheumatology as follows:
| Name of subtype | Number of joints involved during the first 6 months | Joints affected | Likelihood of anterior uveitis |
|---|---|---|---|
| Oligoarticular | 4 or fewer | Mostly knees then ankles and wrists | 20% |
| Polyarticular (rheumatoid factor negative) | 5 or more | Small and large joints symmetrically | 5-10% |
| Polyarticular (rheumatoid factor positive) | 5 or more | Hands, wrists and knees (similar to adult rheumatoid arthritis) | very low risk |
| Systemic (aka Still’s disease) | n/a | Knees and wrists. Although systemic features often occur prior to arthritis. | rare |
Children are often initially asymptomatic and therefore screening is important to monitor any development of ocular manifestations (see below). If there is sufficient inflammation then they may complain of occasional floaters or decreased visual acuity.
Screening is performed with a slit lamp and looks for signs of active inflammation such as aqueous flare (protein seeping from blood vessels into the anterior chamber fluid). If this is present then there is a higher risk of long-term complications, especially if present at the initial appointment.
Long-term complications include:
There is also a higher chance of chronic rather than acute anterior uveitis (where symptoms are present for longer than 3 months). Click here to read more about the classic features of anterior uveitis.