Background Lupus nephritis (LN) frequently occurs in the clinical course of childhood-onset systemic lupus erythematosus (cSLE) and is involved in higher long-term morbidity and mortality of the disease compared to adults. Avoiding a progression to end-stage renal disease and, in the same time, minimizing current toxic treatment regimens is challenging in such young patients. Hence, clinicians need reliable biological markers in order to predict renal involvement. The association of anti-C1q antibodies (Abs) with lupus nephritis in adults is supported by several studies but remains uncertain in children.
Objectives This single center study aimed at investigating the capacity of anti-C1q Abs to predict renal flare at diagnosis and during the follow-up of cSLE.
Methods Anti-C1q Abs assays were performed retrospectively by ELISA in 17 patients from a single tertiary center, presenting with cSLE at diagnosis, at time of a renal flare-up or in a quiescent phase of the disease. Disease activity was measured with SLEDAI score which includes dsDNA aAbs. C3, C4, type I interferon were also analyzed in all patients.
Results Five patients with a renal involvement at diagnosis of cSLE had positive anti-C1q aAbs at a high rate (>200UI/ml) (100%). A total of 11 flares were recorded during the time of the study. Anti-C1q antibodies were positive in 8 of these flares (72,7%). The negativity of anti-C1q Abs during these flares (n=3) was presumably due for one patient to a monogenic form of cSLE associated with a homozygous PRKCD mutation. In the other cases, levels of anti-C1q Abs were just below the limit of positivity and became positive at the time of the next renal flare.
Conclusions Anti-C1q antibodies represent a reliable marker of LN flares in children with cSLE and may be performed routinely during the follow-up of these patients.
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Disclosure of Interest None declared