Overview of IgG4-Related Tubulointerstitial Nephritis and Its Mimickers

Utilizing Immunoglobulin G4 Immunohistochemistry for Risk Stratification in Patients with Papillary Thyroid Carcinoma Associated with Hashimoto Thyroiditis

BACKGRUOUND

Hashimoto thyroiditis (HT) is suspected to correlate with papillary thyroid carcinoma (PTC) development. While some HT cases exhibit histologic features of immunoglobulin G4 (IgG4)-related disease, the relationship of HT with PTC progression remains unestablished.

METHODS

This cross-sectional study included 426 adult patients with PTC (≥1 cm) undergoing thyroidectomy at an academic thyroid center. HT was identified based on its typical histologic features. IgG4 and IgG immunohistochemistry were performed. Wholeslide images of immunostained slides were digitalized. Positive plasma cells per 2 mm2 were counted using QuPath and a pre-trained deep learning model. The primary outcome was tumor structural recurrence post-surgery.

RESULTS

Among the 426 PTC patients, 79 were diagnosed with HT. With a 40% IgG4 positive/IgG plasma cell ratio as the threshold for diagnosing IgG4-related disease, a cutoff value of >150 IgG4 positive plasma cells per 2 mm2 was established. According to this criterion, 53% (43/79) of HT patients were classified as IgG4-related. The IgG4-related HT subgroup presented a more advanced cancer stage than the IgG4-non-related HT group (P=0.038). The median observation period was 109 months (range, 6 to 142). Initial assessment revealed 43 recurrence cases. Recurrence-free survival periods showed significant (P=0.023) differences, with patients with IgG4 non-related HT showing the longest period, followed by patients without HT and those with IgG4-related HT.

CONCLUSION

This study effectively stratified recurrence risk in PTC patients based on HT status and IgG4-related subtypes. These findings may contribute to better-informed treatment decisions and patient care strategies.

IgG4-related kidney disease: Clinicopathologic features, differential diagnosis, and mimics

IgG4-related kidney disease (IgG4-RKD) encompasses all forms of kidney disease that are part of IgG4-related disease (IgG4-RD). First recognized as IgG4-related tubulointerstitial nephritis (IgG4-TIN), and then IgG4-related membranous glomerulonephritis (IgG4-MGN), we now recognize additional patterns of interstitial nephritis, glomerular disease, and vascular disease that can be seen as part of IgG4-RKD. The clinical presentation is variable and can include acute or chronic kidney injury, proteinuria or nephrotic syndrome, mass lesion(s), and obstruction. While usually associated with other organ involvement by IgG4-RD, kidney-alone involvement is present in approximately 20 % of IgG4-RKD. Compared to IgG4-RD overall, patients with IgG4-RKD are more likely to show increased serum IgG4 or IgG, and more likely to have hypocomplementemia. In this review, we extensively cover other types of autoimmune and plasma cell-rich interstitial nephritis, mass forming inflammatory diseases of the kidney, and other mimics of IgG4-TIN, in particular ANCA-associated disease.

A case of eosinophilic granulomatosis with polyangiitis as a mimicker of IgG4-related disease

A 62-year-old woman was admitted to our hospital because of fever, renal dysfunction, eosinophilia, and the presence of MPO-ANCA. Based on the renal pathological examination which showed granuloma lesion with eosinophils and crescentic glomerulonephritis, eosinophilic granulomatosis with polyangiitis (EGPA) was diagnosed. On the other hand, laboratory examination showed elevated serum IgG4 levels and renal pathological examination showed marked lymphoplasmacytic infiltration and fibrosis surrounding nest "Bird's eye pattern," which were characteristic of IgG4-related kidney disease (IgG4-RKD). Because there are cases when EGPA has clinical features of IgG4-RKD, we should be careful about diagnoses of IgG4-RKD in patients with EGPA.

Concurrent anti-neutrophil cytoplasmic antibody-associated glomerulonephritis and IgG4-associated tubulointerstitial nephritis with C3 glomerulonephritis: A case report

RATIONALE

IgG4-related disease (IgG4-RD) is a slowly progressing inflammatory disease that can involve multiple organ systems. There is considerable overlap between IgG4-RDs and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Herein, we present an unusual case of IgG4-associated tubulointerstitial nephritis (IgG4-TIN) and ANCA-associated glomerulonephritis (ANCA-GN) co-occurring with C3 glomerulonephritis (C3GN).

PATIENT CONCERNS

A 72-year-old male was admitted to hospital because of fever and fatigue. He was diagnosed with elevated serum creatinine and IgG4 levels, and was positive for ANCA.

DIAGNOSIS

Initially, the pathology supported a diagnosis of IgG4-TIN and ANCA-GN; however, further examination revealed he also had C3GN.

INTERVENTIONS

The patient was treated with methylprednisolone and cyclophosphamide and received regular follow-up care.

OUTCOMES

After treatment, the patient no longer exhibited fever or fatigue and had no complications. The seven-month follow-up showed downward trends in IgG4 and MPO-ANCA levels and stable 24-hour urine protein, serum creatinine levels.

LESSONS

Anti-neutrophil cytoplasmic antibody-associated glomerulonephritis and IgG4-associated tubulointerstitial nephritis with C3glomerulonephritis rarely occur simultaneously. Laboratory analysis and pathology are both needed to ensure diagnostic accuracy. However, in this case, the three diseases overlapped to such a large extent that achieving a definitive diagnosis was particularly challenging. Timely and accurate diagnosis is crucial for selecting the best treatment course and optimizing patient outcome.

Renal tubular acidosis as the initial presentation of Sjögren's syndrome

We present a 44-year-old female with an initial presentation with distal renal tubular acidosis (RTA) after she presented with hypokalaemia and normal anion gap acidosis. Three years following the diagnosis, she presented with progressive renal impairment. In the absence of any clinical, biochemical and radiological clues, she underwent a renal biopsy which showed severe tubulitis secondary to lymphocytic infiltration. Serological investigations subsequently revealed positive anti-nuclear, anti-Sjögren’s syndrome related antigen A (SS-A), and anti-Sjögren’s syndrome related antigen B (SS-B) antibodies, supporting the diagnosis of Sjögren’s syndrome. This case is unique in that distal RTA was the presenting clinical manifestation of Sjögren’s syndrome. We hope that a consideration for Sjögren’s syndrome is made in patients with seemingly idiopathic RTA.

Baicalein alleviates tubular-interstitial nephritis in vivo and in vitro by down-regulating NF-κB and MAPK pathways

Tubular-interstitial nephritis (TIN) is characterized by tubular cell damage and inflammatory lesions of kidneys. Baicalein (BAI) is a flavonoid compound found in the roots of Scutellaria baicalensis Georgi. The present study was undertaken to explore the anti-inflammatory and anti-oxidative effects of BAI on TIN patients and a lipopolysaccharide (LPS)-induced TIN cell model. The expression levels of interleukin-6 (IL-6), IL-10, and tumor necrosis factor α in serum samples of TIN patients and culture supernatants of renal proximal tubular epithelial cells (RPTECs) were evaluated using enzyme-linked immunosorbent assay. Creatinine clearance was calculated using the Cockcroft-Gault equation. Activities of malondialdehyde, superoxide dismutase, and glutathione peroxidase were also determined. Viability and apoptosis of RPTECs were measured using MTT assay and Guava Nexin assay, respectively. qRT-PCR was performed to determine the expressions of Bax, Bcl-2, nuclear factor kappa B (IκBα), and p65. Protein levels of Bax, Bcl-2, IκBα, p65, c-Jun N-terminal kinase, extracellular regulated protein kinases, and p38 were analyzed using western blotting. We found that BAI reduced inflammation and oxidative stress in vivo and in vitro. Moreover, BAI alleviated the LPS-induced RPTECs viability inhibition and apoptosis enhancement, as well as nuclear factor kappa B (NF-κB), and mitogen-activated protein kinase (MAPK) activation. Phorbol ester, an activator of NF-κB, attenuated the effects of BAI on LPS-induced inflammatory cytokine expressions in RPTECs. In conclusion, BAI had anti-inflammatory and anti-oxidative effects on TIN patients and LPS-induced RPTECs by down-regulating NF-κB and MAPK pathways.

Immunoglobulin G4-related kidney diseases: An updated review

This review will encompass definition, pathogenesis, renal clinical manifestations and treatment of immunoglobulin G4-related diseases (IgG4-RDs). IgG4-RD is a recently recognized clinical entity that often involves multiple organs and is characterized by high levels of serum immunoglobulins G4, dense infiltration of IgG4⁺ cells and storiform fibrosis. Cellular immunity, particularly T-cell mediated immunity, has been implicated in the pathogenesis of IgG4-RDs. The most frequent renal manifestations of IgG4-RD are IgG4-related tubulointerstitial nephritis, membranous glomerulopathy and obstructive nephropathy secondary to urinary tract obstruction due to IgG4-related retroperitoneal fibrosis. IgG4-RD diagnosis should be based on specific histopathological findings, confirmed by tissue immunostaining, typical radiological findings and an appropriate clinical context. The first line treatment is the steroids with two warnings: Steroid resistance and relapse after discontinuation. In the case of steroid resistance, B cell depleting agents as rituximab represent the second-line treatment. In the case of relapse after discontinuation, steroid treatment may be associated with steroid sparing agents. Since the disease has been only recently identified, more prospective, long-term studies are needed to an improved understanding and a more correct and safe treatment.

IgG4-Related Kidney Disease: Report of a Case Presenting as a Renal Mass

IgG4-related disease (IgG4-RD) is a nosological entity defined as a chronic immune-mediated fibro-inflammatory condition characterized by a tendency to form tumefactive, tissue-destructive lesions or by organ failure. Urologic involvement in IgG4-RD has been described in some short series of patients and in isolated case reports, most often involving the kidneys in so-called IgG4-related kidney disease (IgG4-RKD). The disease can occasionally mimic malignancies and is at risk of being misdiagnosed due to its rarity. We report the case of a 56-year-old man presenting with a right renal mass suspected of being malignant. Laboratory tests showed normal creatinine levels, a high erythrocyte sedimentation rate, and high levels of C-reactive protein and microalbuminuria. The patient underwent radical right nephroureterectomy and histopathologic examination revealed features proving IgG4-RKD. He was therefore referred to immunologists. Typical clinical presentation of IgG4-RKD includes altered renal function with inconstant or no radiologic findings. Conversely, in the case we presented, a single nodule was detected upon imaging evaluation, thus mimicking malignancy. This raises the issue of a proper differential diagnosis. A multidisciplinary approach can be useful, although in clinical practice the selection of patients suspected of having IgG4-RKD is critical in the cases presenting with a renal mass that mimics malignancy.

Concurrent IgG4-related tubulointerstitial nephritis and IgG4 myeloperoxidase-anti-neutrophil cytoplasmic antibody positive crescentic glomerulonephritis: A case report

RATIONALE

IgG4-related disease (IgG4-RD) is a newly recognized systemic disease. The typical pathological finding in the kidney is abundant IgG4-positive plasma cell infiltration with characteristic storiform fibrosis in the interstitium. Antibodies of the IgG4 subclass have been linked to certain autoimmune diseases including antiproteinase 3 (PR3) anti-neutrophil cytoplasmic antibody (ANCA) of the IgG4 subclass. Here, we report a rare case of kidney injury with concurrent typical IgG4-related tubulointerstitial nephritis and IgG4 subclass of myeloperoxidase (MPO) ANCA-positive necrotizing crescentic glomerulonephritis.

PATIENT CONCERNS

A 42-year-old Chinese man presented with repeated epigastric pain, sausage-shaped pancreas observed morphologically in computed tomography, effectiveness of prednisone therapy and was diagnosed with autoimmune pancreatitis. He subsequently developed acute kidney injury.

DIAGNOSES

The patient had an elevated serum IgG4, eosinophilia, and positive MPO-ANCA of IgG4-dominant subclass. Renal biopsy revealed necrotizing crescentic nephritis and typical IgG4-related tubulointerstitial nephritis.

INTERVENTIONS

The patient was treated with a combination of corticosteroids and cyclophosphamide, and a course of rituximab was later added to deplete peripheral B cells.

OUTCOMES

The patient responded well and his renal function improved.

LESSONS

This is the first case report of an IgG4-RD with concurrent IgG4-related tubulointerstitial nephritis and IgG4 MPO-ANCA-associated necrotizing crescentic glomerulonephritis. It raises the difficulty in differentiation diagnosis of the two separate diseases that is worthy of further study.