Dr Kazuhiro Takeuchi1,2,3, Dr Kasumi Sato2, Dr Yasuo Takeuchi1, Dr Akira Shimizu3, Dr Mitsuko Iwazaki2
1Kitasato University, Sagamihara/Kitasato, Japan, 2Sagami rinnkan hospital, Sagamihara/Higashirinkan, Japan, 3Nippon medical school, Bunkyo/Nedu, Japan
Biography:
I am a nephrologist specializing in renal pathology, kidney transplantation, and xenotransplantation. My research focuses on large animal models to explore interspecies organ transplantation, aiming to address the global organ shortage. I am committed to advancing scientific understanding and clinical applications in these fields.
Background:
Primary biliary cholangitis (PBC) is commonly associated with autoimmune diseases like rheumatoid arthritis and Sjögren’s syndrome, but its association with systemic lupus erythematosus (SLE) is rare. Lupus nephritis (LN) is characterized by the "full-house" pattern of immunoglobulin (Ig) and complement deposition. A rare phenomenon called "masked IgG" means that IgG is undetectable in frozen tissue, but becomes visible after pronase treatment of formalin-fixed paraffin-embedded (FFPE) tissue.
Case Presentation:
A 69-year-old male with PBC presented with urinary abnormalities and acute kidney injury (AKI). Kidney biopsy revealed necrotizing glomerulonephritis with subepithelial electron-dense deposits, consistent with Class III(A/C) + V LN. Immunofluorescence showed masked IgG, with both light chain κ and lambda positivity, indicating "masked polyclonal IgG." The patient progressed to end-stage renal disease (ESRD) and required hemodialysis. After corticosteroids and mycophenolate mofetil (MMF), renal function gradually improved, and dialysis was discontinued. Six months later, serum creatinine remained stable at 2 mg/dL with MMF and a low dose of steroids.
Conclusion:
This case presents a rare form of lupus nephritis with masked polyclonal IgG, highlighting the unusual coexistence of PBC and SLE. The patient has stable renal function post-dialysis with ongoing treatment.