Background/Purpose: Oligoarthritis, defined as ≤4 affected joints, was recognized as a pattern of psoriatic arthritis (PsA) by Moll and Wright. In some jurisdictions, patients with oligoarticular disease are not able to receive biologic therapy. It remains unclear whether patients with oligoarticular disease differ from those with polyarticular disease and what predicts progression from oligoarticular to polyarticular disease.

Oligoarthritis, defined as ≤4 affected joints, was recognized as a pattern of psoriatic arthritis (PsA) by Moll and Wright. In some jurisdictions, patients with oligoarticular disease are not able to receive biologic therapy. It remains unclear whether patients with oligoarticular disease differ from those with polyarticular disease and what predicts progression from oligoarticular to polyarticular disease.

Methods: Patients followed at the PsA clinic within 1 year of diagnosis were included. Patients were followed according to a standard protocol at 6-12 month intervals. All information was tracked in a computerized database. Oligoarthritis was defined in two ways. First, based on the presence of ≤ 4 inflamed joints, and second based on ≤ 4 involved joints (including both inflammation and damage). Descriptive statistics are provided for patients presenting with oligoarthritis and polyarthritis at baseline. Multivariate Weibull regression models for handling interval- and right- censored data were developed with the outcome being progression to polyarticular disease.  All models are adjusted for age at diagnosis of PsA and gender.

Results:  407 inception patients who had at least two visits were included. Of those 192 presented with oligoarthritis and 215 with polyarthritis. Demographic features were similar in the two groups. As expected, polyarticular involvement was associated with a higher number of actively inflamed joints. The distribution of joints involved was similar in the two group, with small joints of the hands and feet being most commonly involved (Table 1).

Of the 192 patients who presented with oligoarthritis 75 remained oligoarticular and 117 evolved into polyarticular. The only predictor for progressing to polyarthritis was the presence of small hand joint involvement. (Table 2). When we considered oligoarthritis definition based on inflamed and/or damaged joints the predictors for progression included small joints upper extremity as well as use of DMARDs.

Conclusion: Oligoarticular disease is similar to polyarticular disease. Most patients present with upper extremity small joint involvement. The majority of patients who present with oligoarticular disease progress to polyarticular involvement. Patients with oligoarticular disease should be treated aggressively to prevent polyarticular involvement.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/oligoarticular-psoriatic-arthritis/