Objective: Serum IgG antibodies (Abs) to phosphorylated ribosomal (P ribosomal) proteins have been inconsistently associated with neuropsychiatric manifestations in systemic lupus erythematosus (SLE). Our aim was to assess whether serum IgG Abs to ribosomal P proteins are associated with neuropsychiatric SLE.
Patients and methods: We examined an inception cohort of 219 SLE patients. Neuropsychiatric SLE manifestations were characterized using the American College of Rheumatology (ACR) definition. Serum Abs to P ribosomal proteins were searched for by immunoblotting. In a subgroup of patients, Abs were investigated also in cerebrospinal fluid (CSF).
Results: Abs to P ribosomal proteins were detected in 45 (21%) patients, 23 of whom (51%) with neuropsychiatric involvement. Abs to P ribosomal protein were present both in serum and CSF. Abs to P ribosomal proteins significantly correlated with psychosis (p=0.017), mononeuropathy multiplex (p=0.040), malar rash (p=0.004), serum anti-Sm Abs (p=0.042), and lupus anticoagulant (p=0.036). SLE onset age was significantly younger in patients with Abs to P ribosomal proteins. Logistic regression analysis confirmed the relationship between Abs to P ribosomal proteins and psychosis, malar rash, SLE onset age and lupus anticoagulant.
Conclusions: Abs to ribosomal P proteins are associated with psychosis and might be associated with peripheral nervous system complications.