Oligoarticular JIA is the most common subtype of JIA, representing 50% of all JIA (1). Oligo-arthritis affects young girls at least six times more frequently than boys, with a peak incidence below 3 years of age. The prevalence is between 20 and 30 per 100,000, and most ethnic groups are affected (9). Children with this form of JIA have four or fewer joints affected within the first six months of disease, although as many as one-third may subsequently progress to polyarticular involvement (10). Those that subsequently have a cumulative involvement of five or more joints are reclas-sified into the extended oligo-arthritis subtype. Specific exclusions include a positive family history of psoriasis or spondyloarthropathy and a positive rheumatoid factor. Children who remain oligoarticular for five years are unlikely to progress to extended oligo-arthritis.
This group of patients are classically associated with antinuclear antibody (ANA; 40-75%), usually in low titre (less than 1 in 640) with a homogeneous or sometimes speckled pattern. A positive ANA is important in identifying those children at highest risk of developing chronic anterior uveitis, which is the most serious potential consequence of oligo-arthritis JIA (11).
Onset of oligo-arthritis JIA becomes less and less common through adolescence and by adulthood there is no convincing evidence of an adult counterpart of this disease. Although oligo-arthritis does occur in adulthood, this is usually HLA-B27 related; it falls under the spondyloarthro-pathy category and has no ANA or occult uveitis associations.
Was this article helpful?