Phosphatidylserine-Dependent Anti-prothrombin Antibodies as a Key Predictor for Systemic Lupus Erythematosus in Patients with Primary Antiphospholipid Syndrome: A retrospective longitudinal cohort study.

Abstract

Primary antiphospholipid syndrome (PAPS) is an autoimmune disorder characterized by thrombosis and pregnancy morbidity. Although PAPS is distinct from systemic lupus erythematosus (SLE), the two conditions share clinical features and susceptibility genes. Progression from PAPS to SLE is well-recognized. However, risk factors for this transition are poorly understood. We aimed to identify predictors of progression to SLE in patients with PAPS. A longitudinal single-center study was conducted at Hokkaido University Hospital from 1990 to 2021. Baseline characteristics including clinical features, laboratory data, aPL profiles were compared between patients who progressed to SLE (SLE group) and those who did not (non-SLE group). Among 64 patients diagnosed with PAPS at baseline, nine (13.8%) progressed to SLE over a mean follow-up of 9 years (incidence rate, 1.61 per 100 person-years). At the diagnosis of PAPS, the SLE group had a higher prevalence of anti-phosphatidylserine/prothrombin antibodies (aPS/PT) and anti-dsDNA antibodies compared to the non-SLE group. Other clinical findings, autoantibody profiles, and serum complement levels were similar between the two groups. Multivariate Cox analysis showed that IgG aPS/PT was significantly associated with SLE development (Hazard ratio: 10.3, 95% CI: 1.13-92.6, p=0.04). IgG aPS/PT may be a predictive factor for new-onset SLE in patients with PAPS, suggesting its utility in guiding risk stratification and monitoring strategies for these patients.