Background: Abnormalities in complement activation and clearance of immune complexes by erythrocytes are the central pathogenic mechanisms in systemic lupus erythematosus (SLE). Serum C4d level, which is a degradation product of complement factor C4, was found to be a sensitive indicator of SLE activity. Our aim was to determine whether glomerular C4d staining could be a useful marker of disease activity in patients with lupus nephritis.
Methods: This retrospective study included all consecutive patients who underwent a renal biopsy at our center between January 2005 and December 2009. A total of 29 patients with IgA nephritis were enrolled, and renal biopsy specimens of 24 patients have been evaluated. We evaluated baseline age, sex, hypertension, serum creatinine level, glomerular filtration rate (GFR), urine protein, and glomerular C4d staining. The primary endpoint of this study was the onset of end-stage renal disease (ESRD) in the course of study.
Results: Fourteen (58%) patients were C4d+ and 10 (42%) patients C4d-. Urinary protein excretion was more elevated in C4d+ group (p = 0.0001). The renal biopsy showed that activity index score >12 was a higher proportion in C4d+ patients. The patients were followed up for 3.5 years. Four patients in the C4d+ group evolved to ESRD in the follow-up, but none of the patients in the C4d- group (p = 0.064).
Discussion: We found a relationship between glomerular C4d staining and activity of lupus nephritis. C4d staining may be a useful marker to predict the prognosis of lupus nephritis.