Literature review and case study of predominant tubulointerstitial lupus nephritis

Systemic lupus erythematosus (SLE) is a chronic inflammatory disease that affects multiple organ systems, and lupus nephritis (LN) primarily involves glomerular, vascular and tubulointerstitial lesions. Renal tubulointerstitial lesions are almost always present alongside glomerular lesions, with isolated renal tubulointerstitial LN being very rare. The aim of this study was to evaluate the clinicopathological features, differential diagnosis, treatment and prognosis of predominant tubulointerstitial lupus nephritis (PTILN). We present the case of a 64-year-old Chinese male with severe SLE. The diagnosis of SLE was confirmed on the basis of proteinuria, positive antinuclear antibodies, and immunological and haematological disorders. Renal biopsy revealed severe chronic tubulointerstitial nephritis with excessive immune complex deposition in the tubular basement membrane (TBM), mild glomerular lesions and minimal immune complex deposition, suggesting predominant tubulointerstitial LN. The patient was treated with steroids and mycophenolate mofetil, leading to stabilization of renal function. In the literature review, we identified a total of 18 patients whose predominant tubulointerstitial LN was reported. In our analysis, we evaluated the clinical and pathological features, treatment, and prognosis of this condition in these patients. This case series reinforces PTILN as a distinct LN variant characterized by dominant tubulointerstitial inflammation and TBM immune deposits. Although PTILN shares clinical features with classic LN, PTILN exhibits notable heterogeneity in demographics, pathology, and outcomes, and its pathogenesis, diagnostic criteria, and optimal management require further elucidation.