Membranous nephropathy associated with type 1 autoimmune pancreatitis and dominant glomerular IgG4 deposit

Remission Induction of IgG4-related Membranous Nephropathy with Multitarget Therapy

IgG4-related membranous nephropathy (MN) is often refractory to glucocorticoid (GC) therapy, and treatment remains unclear. We herein report a 67-year-old Japanese man with IgG4-related MN and tubulointerstitial nephritis. A post-gastroscopy antibody test revealed Helicobacter pylori infection. After eradication, his proteinuria decreased indefinitely. We started prednisolone (30 mg/day), long-term GCs, and immunosuppressant therapy. However, remission proved challenging to achieve, with persistent proteinuria present at 1.0-2.0 g/gCr. We performed multitarget therapy for refractory IgG4-related MN, achieving proteinuria remission (<0.3 g/gCr). Multitarget therapy with low-dose GCs can resolve refractory IgG4-related MN through remission induction of proteinuria and minimize the risks associated with GC therapy.

Recent advances in IgG4-related kidney disease

Recent advances in the management and understanding of immunoglobulin (Ig)G4-related kidney disease (RKD) have emphasized the importance of urgent treatment in IgG4-related tubulointerstitial nephritis. On the other hand, to avoid long-term glucocorticoid toxicity, strategies for early withdrawal of steroids or combination of immunosuppressants, such as rituximab, and the minimum dose of steroids have been pursued. However, disease recurrence after reducing or stopping steroid therapy hampers early withdrawal of glucocorticoid maintenance therapy. In addition, knowledge has accumulated in diagnostic approaches including differential diagnosis of anti-neutrophil cytoplasmic antibodies-associated vasculitis, idiopathic multicentric Castleman's disease, and Rosai-Dorfman disease with kidney lesion, which leads to earlier and precise diagnosis of IgG4-RKD. This review summarizes recent progress in the differential diagnosis of IgG4-RKD and related treatment strategies and recent topics of hypocomplementaemia, membranous glomerulonephritis, and IgG4-related pyelitis and periureteral lesion.

Establishment and application of an immunoassay for the simultaneous detection of IgG and its subtype IgG4 autoantibodies against M-type phospholipase A2 receptor

BACKGROUND

The renal biopsy is an accurate and reliable gold standard for membranous nephropathy (MN) diagnosis. However, it is an invasive procedure involving the risk of hemorrhage or infection. Thus, an alternative approach that can facilitate the effective diagnosis and treatment monitoring of idiopathic membranous nephropathy (IMN) is urgently needed.

METHODS

We established a dual-labeled time-resolved fluoroimmunoassay (TRFIA) to simultaneously detect phospholipase A2 receptor (PLA2R)-IgG4 and PLA2R-IgG antibodies. Utilizing this assay, we determined the ratio of autoantibodies in the serum of patients with different kidney diseases and normal controls.

RESULTS

The sensitivity of TRFIA for detecting anti-PLA2R-IgG and anti-PLA2R-IgG4 was 0.12 µg/mL and 0.001 µg/mL, respectively. Human IgA did not interfere with the assay. Compared to anti-PLA2R-IgG alone, the positive rate of IMN could be increased from 86.5 % to 91.7 % through the combined use of anti-PLA2R-IgG4 and the PLA2R-IgG4/IgG ratio. In contrast, the false-positive rates for the detection of IgA nephropathy, lupus nephropathy, diabetic nephropathy, and minimal change nephropathy decreased from 25 to 50 % to 0 %.

CONCLUSIONS

The dual-labeled PLA2R-IgG4/IgG-TRFIA for simultaneous detection of anti-PLA2R-IgG4 and anti-PLA2R-IgG will contribute to improved accuracy of IMN diagnosis.

Low-density lipoprotein apheresis for PLA2R-related membranous glomerulonephritis accompanied by IgG4-related tubulointerstitial nephritis

IgG4-related disease preferentially involves the kidney by tubulointerstitial nephritis with IgG4-positive plasma cell filtration and/or membranous glomerulonephritis. We reported the case of a 68-year-old man with IgG4-related tubulointerstitial nephritis combined with antiphospholipase A2 receptor (PLA2R)-related membranous glomerulonephritis, in which distinguishing between idiopathic PLA2R-related and IgG4-related secondary membranous glomerulonephritis was difficult. We diagnosed him as having IgG4-related disease, based on a serum IgG4 level of 170 mg/dL and the presence of IgG4-related parotiditis. On renal biopsy, there was tubulointerstitial nephritis with IgG4-positive plasma cell filtration, which was compatible with IgG4-related disease and membranous glomerulonephritis, with concomitant positive staining for PLA2R on immunofluorescence microscopy. The renal function immediately recovered after steroid treatment, probably because of the improvement in the tubulointerstitial lesions, but his nephrotic syndrome was steroid-resistant. Low-density lipoprotein (LDL) apheresis therapy was effective for membranous glomerulonephritis and increased his serum albumin from 1.4 to 2.8 g/dL. Although IgG4-related kidney disease usually accompanies secondary membranous glomerulonephritis, the positive PLA2R staining suggested a concomitant primary membranous glomerulonephritis. The recent treatment strategy, including LDL apheresis, for primary and secondary membranous glomerulonephritis was discussed briefly in this report.

PLA2R-Negative Membranous Nephropathy Presenting as a Prodrome of IgG4-Related Autoimmune Pancreatitis

Membranous nephropathy (MN) with tubulointerstitial nephritis (TIN) is an established manifestation of immunoglobulin G4 (IgG4)-related disease (IgG4-RD). A pathological feature aiming to distinguish between primary and secondary MN is the presence or absence of glomerular staining for phospholipase A2 receptor (PLA2R), respectively. Isolated MN without TIN has been rarely reported in the context of IgG4-RD. This case report describes a patient with a history of MN successfully treated with steroids and cyclophosphamide, who, 3 years later, presented with unexplained exacerbation of diabetes mellitus due to IgG4-related autoimmune pancreatitis. Pancreatitis was treated, and diabetes improved after treatment with steroids. Based on the presence of isolated IgG4 glomerular capillary deposits along with negative staining for PLA2R and the metachronous appearance of autoimmune pancreatitis, MN was retrospectively classified as secondary to IgG4-RD. Isolated IgG4-positive/PLA2R-negative MN without TIN can be a prodrome of IgG4-RD, reminiscent of MN secondary to neoplasms.

A Refractory Case of Secondary Membranous Nephropathy Concurrent with IgG4-related Tubulointerstitial Nephritis

A 58-year-old man with type 1 autoimmune pancreatitis was referred to nephrologists for severe proteinuria. Laboratory data revealed a high serum IgG4 level, hypoalbuminemia, and massive proteinuria, which were compatible with nephrotic syndrome. The renal pathological findings confirmed the diagnosis of secondary membranous nephropathy concurrent with IgG4-related tubulointerstitial nephritis. Despite the improvement of interstitial markers, the proteinuria was refractory to prednisolone, requiring cyclosporine to achieve complete remission. Membranous nephropathy is a rare manifestation of IgG4-related kidney disease. This case shows that the therapeutic response to prednisolone significantly differs between glomerular lesions and interstitial lesions of IgG4-related kidney disease.