The importance of tubuloreticular inclusions in lupus nephritis

Tubuloreticular inclusions (TRI) are distinctive cytoplasmic structures of unknown origin that typically associate with autoimmune and viral diseases. We investigated the clinical and prognostic relevance of TRI detection in patients with lupus nephritis (LN). We conducted a single centre study of patients (n=84) with biopsy evidence of LN. Clinical variables included demographics, SLEDAI score, and autoantibody profiling; while histological evaluation included TRI presence, International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification with NIH activity and chronicity indices, immunofluorescence, and other EM findings. Patients with and without TRI were compared by non-parametric statistical methods and survival analysis for the endpoints of death and renal failure. TRI were detected in 37 patients (44%) that were younger (28.4 vs 34.3 years, p=0.02) and more often from Asian background (37.8% vs 19.1%, p=0.04) compared to patients without TRI. SLEDAI score (11 vs 12 units, p=0.36) and amount of proteinuria (370 vs 340 mg/mmol, p=0.71) were similar in both groups; however, TRI positive patients had increased frequency of anti-SSB antibodies (16% vs 2%, p=0.02), 'full house' immune complex deposition (85% vs 58%, p=0.04) and subendothelial electron dense deposits (83% vs 65%, p=0.07), but were less often anti-dsDNA Ab positive (62% vs 85%, p=0.02). Patient and renal survival were not influenced by TRI status. TRI were observed in nearly half of all LN patients and TRI positive patients more often carried anti-SSB antibodies. However, TRI had little bearing on disease presentation or outcome in LN.