Background Previously, we reported a different renal prognosis between two onset categories of lupus nephritis (LN): LN that developed as a flare of systemic lupus erythematosus (SLE) after treating the prior non-renal SLE conditions successfully (delayed, D-LN) and LN manifesting at the time of SLE onset (early, E-LN).1) D-LN had a poorer renal prognosis than E-LN independent of the renal histology based on the chart review, but we had not analyzed the serological data in those LN patients.
Objectives This study investigated possible differences in the serological profiles and activities between E-LN and D-LN. We focused on the serum levels of complement C3 and anti-ds DNA antibodies (Ab) as serological activities, and anti-Sm Ab as a serological profile.
Methods Our hospital records for 1990–2015 were reviewed, and we identified 361 SLE patients diagnosed according to the American College of Rheumatology criteria for SLE. This study had two parts.
1. Serological activity (C3 and anti-dsDNA Ab): Of the 361 patients, 166 with LN (83 E-LN, 83 D-LN) had serum C3 and anti-dsDNA Ab levels measured on each admission to treat a total of 347 active SLE events (204 renal and 143 non-renal events). The serum data were compared between the E-LN and D-LN groups using the Mann–Whitney U-test and two-way analysis of variance (ANOVA).
2.Prevalence of positive serum anti-Sm Ab: From the 361 patients, we enrolled 129 patients diagnosed with SLE between Jan. 1996 and Oct. 2010 who were observed for more than 5 years. Patients diagnosed before 1996 were excluded because comprehensive anti-Sm Ab data were not available. Anti-Sm-Ab-positive patients were defined by at least once positive result before or at an LN manifestation. The frequency of anti-Sm-Ab-positive patients was compared among three patient-groups: E-LN, D-LN, and non-LN-SLE (the patients with no LN for more than 5 years).
Results 1. The treated SLE conditions in the 83 E-LN patients included 91 renal events (35 flares) and 36 non-renal events, and those in the 83 D-LN patients comprised 113 renal events (52 flares) and 107 non-renal events. Serum anti-dsDNA Ab levels were higher in D-LN than in E-LN for the renal events (169 ± 139 IU/mL (EIA), n=98 vs. 120 ± 143 IU/mL, n=73, p<0.01) and renal flare events (169 ± 130 IU/mL, n=47 vs. 48.8 ± 79.7 IU/mL, n=35, p<0.01) (Fig). In both the D-LN and E-LN groups, the serum anti-dsDNA Ab levels were higher at renal events than non-renal events. The serum C3 levels were similar in the D-LN and E-LN groups during renal events.
2. The enrolled patients comprised 39 E-LN, 23 D-LN, and 67 non-LN-SLE. The frequency of anti-Sm-Ab-positive patients was higher in D-LN than non-LN-SLE (15/23, 65.2% vs. 16/67, 23.9%, p=0.001) and higher in D-LN than E-LN (15/23, 65.2% vs. 12/39, 30.8%, p=0.016).
Conclusions High serum anti-dsDNA Ab titers were characteristic of LN that developed later in the course of an SLE flare (D-LN) compared with LN manifesting at the onset of SLE (E-LN). D-LN may reflect intractable SLE conditions. Positive serum anti-Sm antibodies were prevalent in D-LN patients in our study. Therefore, anti-Sm-Ab-positive SLE patients without LN may be at risk for the subsequent development of D-LN.
Takahashi Y, et al. Time of initial appearance of renal symptoms in the course of systemic lupus erythematosus as a prognostic factor for lupus nephritis. Mod Rheumatol 2009; 19: 293–301
Disclosure of Interest None declared