CHARACTERIZING ARTHRITIS SUBTYPES IN SLE: PREVALENCE, CLINICAL FEATURES, AND THE ROLE OF TYPE I INTERFERON SIGNATURES

O031 / #611

Topic: AS23 - SLE-Diagnosis, Manifestations, & Outcomes

ABSTRACT CONCURRENT SESSION 05: EMERGING INSIGHTS ON THE MANAGEMENT OF LUPUS MANIFESTATIONS AND COMORBIDITIES

23-05-2025 1:40 PM - 2:40 PM

Background/Purpose Musculoskeletal involvement in Systemic Lupus Erythematosus (SLE) is one of the most prominent manifestations of the disease, featuring in both the classification criteria and disease activity assessments. It is presently unclear if specific subtypes of lupus arthritis—nondeforming nonerosive (NDNE), Jaccoud’s arthropathy (JA), and rhupus, are associated with specific clinical associations. We aimed to study the prevalence of subtypes of lupus arthritis and determine their association with clinical features, serology, and type I interferon signature.

Methods This is an observational cohort study of patients with arthritis (defined by the ACR or EULAR/ACR SLE classification criteria at presentation and SLEDAI 2K over follow-up) identified from a single-center SLE database (July 1970-Aug 2024) from both inception and prevalent cohorts. Demographic, clinical, laboratory (including interferon signature), radiographic features, and treatment variables were retrieved from the database. Descriptive statistics were used to outline features across 3 subtypes of arthritis; nondeforming arthritis (determined by clinical examination), arthritis with reducible deformities or JA, and arthritis with nonreducible deformities or rhupus. In the inception cohort, time to deformities was studied using cumulative incidence survival analysis. Factors associated with deforming arthritis were determined using multivariate Fine and Gray modeling as a time-to-event analysis for the inception cohort using age, sex, smoking, adjusted mean SLEDAI-2K, autoantibodies, complements, antimalarial, glucocorticoid, and immunosuppression use.

Results Arthritis was observed in 1,248 of 2264 (55.12%) patients. 908 (72.6%) had nondeforming and 340 (27.2%) had deforming arthritis–239 (19.2%) had JA, 101 (8.1%) had rhupus. The median age at diagnosis of SLE was comparable, though a higher proportion of females was observed in JA (p=0.03). The distribution of organ involvement and antibodies was similar across the 3 subtypes, except nervous system involvement (p=0.03) and anti-Ro antibodies (p=0.04) being more frequent in rhupus. There was a trend toward higher mean SLEDAI-2K scores in JA (p=0.07), and the modified SDI (excluding musculoskeletal component) was the highest in rhupus (p<0.01). The distribution of rheumatoid factor and anticitrullinated protein antibody positivity did not differ significantly across the 3 groups. The proportion of patients with high interferon signature was the greatest in JA, followed by nondeforming arthritis, and lastly, rhupus (p<0.01). Radiographs (n, 95) revealed erosive disease in 10 of 43 (23.2%) with JA, 12 of 36 (33.3%) with rhupus, and 2 of 16 (12.5%) with nondeforming arthritis. The use of glucocorticoids, mycophenolate mofetil, belimumab, and other biologics was most prevalent in JA, while methotrexate was higher in rhupus. (Table 1) In the inception cohort, the cumulative incidence plot showed a shorter time to the development of JA of 2.07 [1.00, 15.76] as compared to 4.64 [1.00, 9.78] years for rhupus. In the multivariate analysis, JA was associated with a higher adjusted mean SLEDAI 2K [1.09(1.01-1.19)] and female sex [3.3(1.14-12.5)]. No significant associations were observed with rhupus.

Conclusions Arthritis was observed in half the cohort, with the majority being nondeforming (72.6%). Among deforming arthritis, JA (19%) was more common than rhupus (8%). JA was associated with a high interferon signature, high disease activity, female sex, and a shorter time to development as compared to rhupus. These sheds light on 2 different mechanisms for deforming arthritis, with JA associated with SLE disease burden in contrast to rhupus. Erosions were observed in both types of deforming arthritis, blurring the line of radiologic differences historically outlined between them.