Clinical features of oligoarticular Juvenile Idiopathic Arthritis
What are the demographics and clinical characteristics of oligoarticular Juvenile Idiopathic Arthritis?
Oligoarticular JIA is defined as the involvement of one to four joints during the first 6 months of disease. It usually presents as an asymmetric large joint arthritis with the knee most commonly involved. It is the most common subcategory of JIA in North America/Europe. Notably, this disease is unique to pediatric patients because there is no adult equivalent. Oligoarticular JIA may present only with a limp and minimal complaints of pain. Most commonly involved joints are the knee, then ankle, and wrists. Involvement of fingers should raise concern for possible psoriatic arthritis. Hip and back pain is unusual; a child complaining of pain in these areas needs a workup for other etiologies.
- • Peak age of onset in whites: 2 to 4 years.
- • Gender ratio: female > male 3:1.
- • Two subgroups of arthritis defined after 6 months:
- • Persistent: never more than one to four joints involved
- • Extended: more than four joints involved after the first 6 months of disease. This develops in 30% to 50% of patients, especially in those with symmetric joint involvement, wrist or ankle involvement, and an elevated ESR at onset.
- • Laboratory abnormalities: ANA is positive in 75% to 85% of cases. It is low titer, ≤1:320. More commonly positive in young girls. RF is negative, white blood cell count is normal, and acute-phase reactants are only mildly elevated. Any fever, iron-deficiency anemia, or significantly elevated ESR/C-reactive protein (CRP) should suggest septic arthritis, inflammatory bowel disease arthritis, or malignancy.
- • Chronic nongranulomatous anterior uveitis: Uveitis is a serious complication of JIA that is often asymptomatic and can lead to blindness if not identified and adequately treated. It is most commonly seen in ANA-positive girls with oligoarticular JIA who are aged <7 years. Uveitis can precede arthritis in 10% of cases. If there is any suspicion of oligoarticular JIA in a patient under the age of 7, a baseline eye exam is strongly recommended.