Comparison of lupus nephritis and non-lupus nephritides in patients with systemic lupus erythematosus

Objective: Kidney biopsy may unusually show non-lupus nephritis (LN) causes in patients with systemic lupus erythematosus (SLE). This study aimed to reveal the causes of non-LN and to compare the clinical and laboratory features of LN and non-lupus renal disease in patients with SLE. Methods: Patients with SLE followed between 2014 and 2020 at Hacettepe University Hospitals and who had kidney biopsy were the subject of the study. One hundred thirty four patients’ kidney biopsies were evaluated retrospectively and grouped as LN and non-LN. Clinical characteristics, laboratory values at the time of kidney biopsy, and renal outcome were recorded. Results: Of 134 (107 females, 27 males) patients, 116 (86.6%) were in the LN group, and 18 (13.4%) were in the non-LN group. The most common diagnosis was focal segmental glomerulosclerosis (n=6) in the non-LN group. The median (interquartile range) biopsy age of LN patients was young [21 (17.7) vs. 36.5 (17), p<0.001], and high titer antinuclear antibody positivity over 1/320 at SLE diagnosis was more frequent in this group (50.9% vs 22.2%, p=0.02). Non-renal SLE involvement was similar in both groups. Anti-dsDNA positivity, low C3-4, and presence of active urinary sediment were significantly higher in LN patients, while serum creatinine, albumin, and proteinuria were not different between the groups at the time of kidney biopsy. Additionally, median renal SLEDAI was more elevated in LN patients. Conclusion: Anti-dsDNA positivity, low C3-C4, active urinary sediment, and high renal SLEDAI scores may give us some clues regarding renal disease in patients with SLE. However, it should be kept in mind that these serological abnormalities may also occur in non-lupus renal disease.