Objective: Antibodies to C1q (aC1q) have been found in up to 50% of adult patients with systemic lupus erythematosus (SLE) and have been associated with proliferative glomerulonephritis. We investigated the prevalence and clinical significance of aC1q in pediatric SLE.
Methods: Antibodies to C1q, measured by an ELISA method, were evaluated in 29 patients with childhood-onset SLE, 26 females and 3 males, aged 7.5 to 19.6 years.
Results: Seventeen (59%) of the 29 patients were initially positive for aC1q. No correlation was found between either the presence or titer of aC1q and any of the clinical manifestations, including nephritis. However, a significant correlation was observed between aC1q levels and anti-double-stranded DNA antibodies and C3 values. Serial determinations of aC1q in 23 patients showed a progressive decline in the titers with few significant fluctuations. Antibodies to C1q were not a reliable predictor of increased SLE activity, since they increased or became detectable in only 50% of the pre-flare sera.
Conclusion: Antibodies to C1q were frequently positive in our patients with pediatric SLE and were correlated with laboratory variables of disease activity. However, unlike in adults with SLE, a high correlation between aC1q and glomerulonephritis was not found in these pediatric patients.