#6899 microvascular lesions in lupus nephritis

Abstract Background and Aims Microvascular lesions (MVL) can be found in the kidneys of lupus nephritis (LN) patients and might be associated with worse outcomes. There are very few studies which evaluated MVLs in these patients and we aimed to provide a comprehensive evaluation of all MVLs, their frequency, characteristics and association with renal outcomes one year after kidney biopsy. Method We have conducted a retrospective cohort study to evaluate the characteristics and prognostic significance of MVLs in the kidney of subjects with LN. We have collected data on demographics, clinical and laboratory parameters and histopathology (light, immunofluorescent and electron microsopy). MVLs were characterized according to previous classifications. SLE was diagnosed using the American College of Rheumatology criteria. Results A total of 56 patients with biopsy-proven LN were followed up for at least one year after kidney biopsy (79% women, mean age at biopsy 38±13 years). Forty patients (71%) had MVLs in the kidney. The most common MVLs were arteriolar endotheliocyte swelling (54%), arteriolar hyalinosis (25%) and endothelialitis (8%) and the frequency distribution of all microvascular lesions is shown in Figure. Median number of lesions in the MVL group was 1 (interquartile range 1 to 2) and subjects had up to 6 MVLs. There was no difference in the median number of MVLs across LN classes (p>0.05). Proteinuria was highest in class V (5.5 g/day, p = 0.06 vs. all other classes). Subjects with MVLs had lower baseline proteinuria compared with those with no lesions (3.6 vs. 5.4 g/day, p = 0.037), but there was no difference in serum creatinine (92 vs. 119 umol/L, p = 0.25). There were no differences in the occurrence or number of MVLs across LN classes (p = 0.63). The number of MVLs was not correlated with proteinuria (p>0.05). There was no difference in the frequency of proliferative lupus between MVL and no MVL groups (79% vs. 60%, p = 0.15). A total of 48% of subjects achieved complete response (CR), 27% achieved partial response (PR) and 25% had no response (NR). MVLs were not associated with response (defined as CR or PR) in a multivariate regression model (OR 3.5 [0.5, 24.6]). Conclusion MVLs are common in LN. They were associated with lower baseline proteinuria, but not with proliferative LN or renal outcomes. The association with proteinuria warrants further research.