Performance of the EULAR/ACR 2019 classification criteria for systemic lupus erythematous in monogenic lupus.

Objective: To evaluate the application of the EULAR/ACR-2019 criteria to monogenic lupus patients and compare its performance against the SLICC-2012 criteria.

Methods: In a multicenter retrospective cohort study, consecutive patients with monogenic lupus from three tertiary lupus clinics were enrolled. The diagnosis of monogenic lupus was based on the expert physician's opinion or fulfilling the SLICC-2012 criteria. All enrolled patients had genetic variants. A control group of sporadic childhood SLE (cSLE) and non-SLE patients, were included. A descriptive data analysis was conducted, and the EULAR/ACR-2019 and SLICC-2012 criteria were applied to both groups.

Results: Forty-nine patients with monogenic lupus with a median age at diagnosis of 6.0 (IQR 3.0-10.8) years and 104 controls (55 patients with cSLE and 49 non-lupus patients with a median age at diagnosis of 10.0 and 5.0 respectively) were included. Forty-four (89.8%) patients with monogenic lupus fulfilled the EULAR/ACR-2019 with a mean score of 22.3±8.9. The most frequent domains were immunologic (93.9%), musculoskeletal and renal (each 57.1%), and mucocutaneous (55.1%). Fifty-four (98.2%) cSLE patients and six (12.2%) non-lupus patients met the EULAR/ACR-2019 criteria with a mean score of 22.5±9.2 and 8.5±5.2, respectively. The sensitivity of the EULAR/ACR-2019 criteria in monogenic lupus was 89.9% (95% CI: 78.3-90.2), while the specificity was 87.6% (95% CI: 75.2-88.7).

Conclusion: This is the first and largest cohort of monogenic lupus patients testing the performance of the 2019-EULAR/ACR criteria. It efficiently classifies monogenic lupus patients, irrespective of the underlying genetic variants. Further studies are needed before these criteria are adopted worldwide. Key Points • Typically, patients with monogenic lupus have early onset severe disease, especially with mucocutaneous manifestations and a strong family history of SLE. • Monogenic lupus is a distinctive entity and might differ from the sporadic childhood SLE. • Our study includes a large multinational cohort of monogenic lupus with heterogeneous phenotypic features and underlying genetic variants. • Our study demonstrates that the EULAR/ACR-2019 criteria efficiently classified monogenic lupus patients, irrespective of the diversity of the underlying genetic variants.