Background/Purpose: Foot involvement is well recognized in many inflammatory rheumatic diseases, namely in Spondylarthritis (SpA), where its early recognition is of utmost importance. Psoriatic arthritis (PsA), although included in SpA group, is an individual entity with characteristic features. Foot involvement in PsA is frequent and often develops early in the disease’s course, proving diagnostic and prognostic information. The purpose of this study was to evaluate and describe foot involvement in a group of patients with PsA.

Methods: Single-center, retrospective study including patients with PsA (all patients fulfill CASPAR criteria) followed in our center over a period of five months (from January-May 2022). Patients were divided into two groups: with current or previous foot involvement (assessed clinically or by ultrasound) (group 1) and without current or previous foot involvement (group 2). Sociodemographic, clinical, laboratory and radiological data were collected. Multimorbidity was defined as 2/+ comorbidities.

Descriptive analysis was performed. Clinical, laboratory and radiological findings were compared between groups, with a p-value ≤ 0.05, with SPSS® software.

Results: 150 patients were enrolled. The mean age was 56.92 years, and 38.7% were women, without statistically significant differences between groups. Foot involvement was found in 104 patients (69.3%). Arthritis was found in 93 patients (62.0%), with the tibiotarsal joint as the most frequent site (30.0% of patients). Enthesitis was found in 28.0% (42 patients), with calcaneal tendonitis as the most frequent manifestation (10.6% of patients). 18.6% (28 patients) had current/previous dactylitis. Radiological findings showed osteopenia in 26.6% of patients, symmetrical joint space narrowing in 12.0%, 20.0%, and 10.0% in tibiotarsal, metatarsophalangeal and Interphalangeal joints, respectively. Erosions were found in 28.6% of patients.Extra-articular manifestations were significantly more prevalent in the group with foot involvement (p=0.03)We found statistically significant higher HAQ disability index values in group 1 [median 1.00, IQR 0.875 (group 1) VS median 0,0625, IQR 0.875 (group 2); p< 0.01]; Multimorbidity was also more frequent in group 1 [58.6% (group 1) VS 37.7% (group 2); p=0.02];Patients with foot involvement had higher C-reactive protein (CRP) [median CRP 1.17, IQR 1.58 (group 1) VS median CRP 0.26, IQR 0.56 (group 2); p=0.01] and erythrocyte sedimentation rate (ESR) [Median ESR 28.00, IQR 21.00 (group 1) VS Median ESR 8.00, IQR 17.00; p=0.01)] levels, and were more frequently under steroids (p=0.01) and non-steroidal anti-inflammatory drugs (NSAIDs) (p=0.02).

Conclusion: Our results suggest that foot involvement is frequent in patients with PsA and is associated with the presence of multimorbidity and extra-articular manifestations, as well as with higher rates of steroids and NSAIDs. Patients with foot involvement had higher HAQ disability index levels, reflecting the negative impact of foot involvement in daily functionality in these patients. Considering that, our study highlights the importance of using activity indices that include foot involvement to better represent the disease’s activity in PsA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/foot-involvement-in-psoriatic-arthritis-a-retrospective-study/