Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Objective: To investigate the prevalence of the anti-ribosomal P (anti-P) antibodies in childhood-onset systemic lupus erythematosus patients (cSLE), healthy controls and first degree relatives. To elucidate the association between anti-P and disease activity, laboratory and treatment features in cSLE patients. Methods: We included consecutive SLE patients with disease onset before 16 years. Controls were age- and sex-matched. SLE patients were assessed for clinical and laboratory SLE manifestations, disease activity (SLE Disease Activity Index (SLEDAI)), damage (Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI)) and current drug exposures. Mood disorders were determined through Becks Depression and Becks Anxiety Inventory. Anti-P measured by enzyme-linked immunosorbent assay. Results: We included 50 consecutive cSLE patients (mean age of 16.82 +/- 3.46 years), 35 first degree relatives (mean age of 38.73 +/- 3.89 years) and 20 health control (mean age of 18.3 +/- 4.97 years). Anti-P was observed in 13 (26%) cSLE patients and in no first-degree relative (p < 0.01) or control (p < 0.01). Anti-P was more frequently observed in patients with anxiety (p < 0.002). No other clinical, laboratory or treatment features, including SLEDAI and SDI scores were associated with the presence of anti-P in cSLE patients. Conclusion: Anti-P is frequently observed in cSLE patients and was associated with the presence of anxiety in this cohort of cSLE. Lupus (2012) 21, 1225-1231.211112251231Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [FAPESP 2008/02917-0, 2009/06049-6, 2009/13046-3]CNPq [300447/2009-4]