Vitoria Paes de Faria
1* 
, David João
2 , Susana Pereira
1 , Ana Marta Gomes
1,3 , Maria Clara Almeida
1, Rute Carmo
1 1 Nephrology Department, Centro Hospitalar Vila Nova de Gaia/Espinho, Vila Nova de Gaia, Portugal
2 Pathology Department, Centro Hospitalar Vila Nova de Gaia/Espinho, Vila Nova de Gaia, Portugal
3 Department of Nephrology, Dialysis and Transplantation, UMIB - Unit for Multidiscisciplinary Research on Biomedicine, ICBAS—
4 School of Medicine and Biomedical Sciences, University of Porto, Porto, Portugal
Abstract
Idiopathic tubulointerstitial nephritis (TIN) with hypocomplementemia is a rare cause of progressive renal failure, with IgG4-related disease (IgG4-RD) emerging as an important differential diagnosis. Within IgG4-RD spectrum, renal involvement frequently reported however, renal involvement alone is uncommon. We present a case of a 66-year-old male with progressive kidney dysfunction. Clinical evaluation revealed bilateral inguinal adenopathies and laboratory findings showed elevated IgG and IgG subclass 4 levels, along with low-complement. Renal biopsy confirmed extensive TIN with marked lymphoplasmacytic infiltrates and elevated IgG-positive cells, consistent with IgG4-RD. The patient was initiated on glucocorticoid therapy, resulting in partial recovery of renal function. Long-term follow-up demonstrated stable renal function and absence of systemic manifestations of IgG4-RD. This case highlights the importance of considering IgG4-RD in the differential diagnosis of TIN with hypocomplementemia. Glucocorticoids remain the first-line treatment, although alternative regimens may be considered to minimize relapse rate and long-term steroid related toxicity. Timely recognition and management of IgG4-related TIN are essential to prevent irreversible kidney damage and improve long-term outcomes.
Implication for health policy/practice/research/medical education:
The description of the rare clinical scenario of renal limited IgG4 disease, management and long-term follow up allows for shared learning experience among clinicians.
Please cite this paper as: Paes de Faria V, João D, Pereira S, Gomes AM, Almeida MC, Carmo R. Tubulointerstitial nephritis with hypocomplementemia in IgG4-related kidney disease; a case report and follow-up of a mysterious entity. J Nephropathol. 2025;x(x):e25548. DOI: 10.34172/jnp.2025.25548.