CHARACTERISTICS OF IGG4 RELATED RENAL DISEASE IN KIDNEY BIOPSY – CASE SERIES

Introduction:

IgG4 related diseases are the spectrum of systemic fibroinflammatory diseases that can involve multiple organs. IgG4 related diseases show lymphoplasmacytic infiltration, storiform fibrosis, obliterative phlebitis, increased IgG4 positive plasma cells in the biopsy. There is increase in serum IgG4 levels. The renal manifestations in IgG4 related diseases could be due to IgG4 related renal disease or secondary to retroperitoneal fibrosis. IgG4 related renal diseases exhibit varied patterns in the renal biopsy. We document the case series with biopsy diagnosis of IgG4 related renal disease.

Methods:

We obtained all the consecutive native kidney biopsies with the diagnosis of IgG4 related renal disease from August 2013 to August 2024. The pathology slides were stained with haematoxylin eosin, Jones silver methenamine, Masson trichrome and periodic acid Schiff. IgG4 immunostaining was performed in all the cases. The clinical characteristics were retrieved from the database.

Results:

53 cases of IgG4 related renal disease were identified. Male: female ratio was 2.3:1. The mean age at diagnosis was 56.1±12.1. The clinical presentation was acute kidney injury (39.6%), rapidly progressive renal failure or RPRF (3.7%), proteinuria (9.4%) and unknown in 47.1%. The mean serum creatinine at presentation was 4±2.1. The comorbidities in the study population include hypertension (26.4%), Diabetes mellitus (20.7%), chronic obstructive pulmonary disease (1.8%) and palmoplantar psoriasis (1.8%). The serum IgG4 levels at the time of biopsy is not available. Two patients were on treatment for IgG4 related systemic disease. All the cases featured IgG4 related tubulointerstitial nephritis, while one case had additional IgG4 related membranous nephropathy. The renal biopsies showed lymphoplasmacytic infiltration with increase in IgG4 positive plasma cells, median 25/high power field (Table 1).

 Storiform fibrosis was noted in 30.1% biopsies. The interstitial fibrosis and tubular atrophy (IFTA) were mild in 49%, moderate in 16.9% and severe in 33.9% cases. Arteriosclerosis was observed in the vessels of 32% biopsies. No obliterative phlebitis or arteritis was present. The case with membranous nephropathy was negative for PLA2R and NELL-1. The additional pathologic findings in the biopsies included Diabetic nephropathy (11.3%), crescentic glomerulonephritis (3.7%), Focal segmental glomerulosclerosis (1.8%) and acute pyelonephritis (1.8%).

Conclusions:

This series highlights the heterogeneity of clinical and histopathological features of IgG4 related renal diseases. The pathologic diagnosis provides directions for systemic evaluation and treatment of the patients.  

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.