Prevalence and Characteristics of Patients With Systemic Sclerosis Fulfilling the 2019 EULAR/American College of Rheumatology Classification Criteria for Systemic Lupus Erythematosus.

Objective: There is limited literature describing the overlap of systemic sclerosis (SSc) and systemic lupus erythematosus (SLE), and the studies have employed a range of case definitions. Our study used the new EULAR/American College of Rheumatology (ACR) SLE classification criteria to define SSc-SLE cases among our center's SSc cohort.

Methods: This is a single-center, retrospective study of a previously described cohort of patients with SSc. Patient data were re-abstracted to evaluate for fulfillment of the 2019 EULAR/ACR classification criteria for SLE. Demographic, laboratory, clinical features, and mortality were compared among patients with SSc-SLE and patients with SSc alone.

Results: Among the 402 patients with SSc that were analyzed, 40 (10%) fulfilled the 2019 EULAR/ACR SLE classification criteria. Neuropsychiatric and renal involvement were rare. An initial SLE diagnosis was purported in 43% of the patients with SSc-SLE and 7% of patients with SSc alone (P < 0.001). Patients with SSc-SLE were more likely to be female, African American, and with limited cutaneous SSc. Anti-U1-RNP antibody positivity prevalence was 30% among patients with SSc-SLE and 6.6% among patients with SSc alone (P < 0.001). Death during follow-up occurred in 12 patients (30%) with SSc-SLE and in 81 patients (22%) with SSc alone, but there was no difference in survival among the groups per log rank test (P = 0.404).

Conclusion: Ten percent of patients with SSc fulfill the 2019 EULAR/ACR classification criteria for SLE. These patients comprise a distinct demographic, serologic, and clinical phenotype but have similar severe SSc-specific end-organ damage and mortality as patients with SSc alone. Patients with SLE with Raynaud phenomenon should be evaluated for SSc-specific autoantibodies and scleroderma organ involvement.