Isolated anti-ribosomal P antibodies are associated with reduced risk of renal and articular involvement in systemic lupus erythematosus patients. An observational study from one center.

Introduction: The aim of the study was to compare the specific clinical manifestations of systemic lupus erythematosus (SLE) or laboratory findings between patients with and without anti-ribosomal P (anti-P) antibodies and to investigate possible associations between isolated anti-P antibodies and these features.

Material and methods: Seventy-five SLE patients were enrolled in this study. They were recruited from the Department of Internal Medicine and Department of Rheumatology at the University Hospital of Monastir, Tunisia (January 2008 - December 2022). All patients met at least four American College of Rheumatology criteria or Systemic Lupus Erythematosus International Collaborating Clinics criteria at the time of disease diagnosis. Antibody typing was performed using a commercial line blot technique. Statistical analysis was performed using the χ² test, Fisher's test when appropriate, Student's t-test, or Mann-Whitney U test according to normality of the data distribution.

Results: Thirty patients (40%) were positive for anti-P (anti-P+). The anti-P+ had higher frequency of skin features (26/49 [53.1%] vs. 4/26 [15.4%], p = 0.003) and central nervous system (CNS) involvement (10/15 [66.7%] vs. 20/60 [33.3%], p = 0.018) than patients without anti-P. Interestingly, anti-P+ showed a lower frequency of SLE/rheumatoid arthritis overlap syndrome (1/11 [9.1%] vs. 29/64 [45.3%], p = 0.042). The comparison between groups of patients according to the presence of anti-P, anti-dsDNA, and anti-Sm showed that the group with anti-P lacking anti-dsDNA and anti-Sm had the highest frequency of neuropsychiatric SLE (75%, p = 0.034), and the lowest frequency of lupus nephritis (0%, p = 0.029) and arthritis (12.5%, p = 0.039).

Conclusions: This study supports the association of anti-P antibodies with CNS and cutaneous manifestations. To the best of our knowledge, this is the first study to report a negative association between isolated anti-P antibodies and renal and articular involvement in SLE.