IgG4-related kidney disease and retroperitoneal fibrosis: An update

IgG4-related disease mimicking a liver abscess

IgG4-related disease (IGRD) is a complex medical condition affecting multiple organs, including the liver. The condition is characterized by excessive production of IgG4 antibodies, leading to chronic inflammation and tissue damage. We present a case of a 37-year-old man with a history of chronic pancreatitis was diagnosed with a liver mass. Initial treatment included piperacillin and tazobactam, but the patient's condition worsened. An ultrasound-guided biopsy revealed increased IgG4 positive cells, leading to the diagnosis of an inflammatory pseudotumor associated with IGRD. The patient was treated with prednisone taper therapy, and the liver mass resolved after six months of corticoid treatment.

Baseline 18F-FDG PET/CT may contribute to the determination of initial treatment strategy for newly diagnosed follicular lymphoma

BACKGROUND

"Watch-and-wait" approach is an important management option in asymptomatic follicular lymphoma (FL) patients with low tumor burden. Since most FL lesions are FDG-avid, we wonder if 18F-FDG PET/CT at baseline can help to better choose the patients who can benefit from early chemotherapy. This study aimed to investigate the prognostic value of baseline 18F-FDG PET/CT in newly diagnosed FL patients treated with either watch-and-wait approach or chemotherapy.

RESULTS

Patients received chemotherapy as initial treatment had higher Ann Arbor stage, higher incidence of extranodal involvement and bulky disease, more involved lymph nodes larger than 3 cm, and higher SUVmax, MTV, and TLG than those managed with watch-and-wait approach (p < 0.05). The median PFS and TTNT in patients received chemotherapy and under watch-and-wait did not show significant difference, however patients with MTV<111.66 mL or TLG<141.50 SUVbw*mL had significantly longer PFS and TTNT than those patients with MTV≥111.66 mL or TLG≥141.50 SUVbw*mL (p < 0.05). Further analysis revealed that for patients with TLG≥141.50 SUVbw*mL or MTV≥111.66 mL, those who received chemotherapy as initial treatment had a significantly longer PFS and TTNT than those managed with initial watch-and-wait approach (p < 0.05). However, for patients with MTV<111.66 mL or TLG<141.50 SUVbw*mL in baseline PET/CT, there was no significant difference in PFS or TTNT between patients who received chemotherapy and those under watch-and-wait.

CONCLUSION

Baseline 18F-FDG PET/CT may provide prognostic value and help to improve the decision-making of initial treatment plans for newly diagnosed FL patients.

Clinicopathologic Features of IgG4-Related Kidney Disease

Introduction

IgG4-related disease (IgG4-RD) is a systemic immune-mediated disease that can involve nearly any organ. IgG4-RD can affect the kidney in different disease patterns, collectively referred to as IgG4-related kidney disease (IgG4-RKD).

Methods

We conducted a tissue-based cohort study with clinicopathological correlation in 125 patients with IgG4-RKD.

Results

The mean age at biopsy (n = 120) or nephrectomy (n = 5) was 63 years; 80% were male. One hundred eighteen patients (94%) had IgG4-related tubulointerstitial nephritis (IgG4-TIN); 20 patients (16%) had IgG4-related membranous glomerulonephritis (IgG4-MGN; 13 with concurrent IgG4-TIN). The primary clinical indication for biopsy/nephrectomy was acute or chronic renal failure in 78%, proteinuria in 17%, and mass lesion(s) in 15% (with overlap in primary indication). Fifty-two percent patients (41/79) had abnormal radiographic findings, including masses in 30% (24/79). All patients with IgG4-MGN had proteinuria. Extrarenal involvement by IgG4-RD was present in 79%. Median serum creatinine at presentation was 2.5 mg/dl (range 0.7-12). Serum IgG and/or IgG4 was increased in 91% (53/58); hypocomplementemia was present in 56% (43/77). Light microscopy showed plasma cell-rich interstitial nephritis in all cases of IgG4-TIN. Ninety-two percent of patients showed increased IgG4+ plasma cells. Seven percent showed an acute interstitial nephritis (AIN) pattern, and 5% showed non-necrotizing arteritis. Tubular basement membrane immune deposits were present in 83% of IgG4-TIN. Treatment information was available for 71 patients; 62 were treated with immunosuppression. Of those with elevated creatinine, 72% (41/57) showed a treatment response.

Conclusion

This largest tissue-based series more clearly defines the disease phenotype of IgG4-RKD.

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.

Clinical phenotypes and prognosis of IgG4-related diseases accompanied by deteriorated kidney function: a retrospective study

INTRODUCTION

IgG4-related disease (IgG4-RD) is a multiorgan autoimmune disorder that causes irreversible injury. Deteriorated kidney functions are common but easily ignored complications associated with IgG4-RD. Yet the clinical manifestations and prognosis of this specific entity have not been fully illustrated.

METHOD

Three hundred fifty patients with IgG4-RD were retrospectively enrolled and divided into 119 IgG4-RD with chronic kidney disease (IgG4-RD CKD+) and 231 IgG4-RD without CKD (IgG4-RD CKD-). Demographic clinical and laboratory characteristics and survival of two cohorts were compared using restricted cubic splines, logistic and Cox regression, and Kaplan-Meier analysis. A nomogram was generated for calculating the probability of CKD in IgG4-RD.

RESULTS

The spectrum of organ involvement was different between IgG4-RD CKD+ and CKD- cohorts (p<0.001). Lung (26.89%) and retroperitoneum (18.49%) involvement were more common in the IgG4-RD CKD+ cohort. Increased serum potassium and phosphorus, reduced calcium levels, and hypocomplementemia (all p<0.05) were observed in IgG4-RD CKD+. Restricted cubic splines revealed a U-shaped plot regarding associations between serum potassium and CKD. Kaplan-Meier analysis demonstrated significantly lower long-term survival rates in IgG4-RD patients with kidney function at CKD stages 4-5. Cox regression revealed declined kidney functions (G4 HR 6.537 (95% CI: 1.134-37.675)) associated with increased all-cause mortality in IgG4-RD patients. A nomogram was constructed to predict CKD in IgG4-RD promptly with a discrimination (C-index) of 0.846.

CONCLUSIONS

CKD in IgG4-RD was associated with poor outcomes and electrolyte disturbances. Patients with IgG4-RD should be aware of possible deterioration in kidney function. The nomogram proposed would help to identify the subtle possibility of CKD in IgG4-RD. Key points • IgG4-related diseases with deteriorated kidney function have specific clinical and laboratory characteristics. • It is crucial to recognize and address the negative impact of deteriorating kidney function in IgG4-related diseases to prevent further harm. • The nomogram proposed would help to identify subtle kidney involvement by evaluating the possibility of CKD in IgG4-related diseases.

Improved Renal Function in Initial Treatment Improves Patient Survival, Renal Outcomes, and Glucocorticoid-Related Complications in IgG4-Related Kidney Disease in Japan

Introduction

We aimed to clarify long-term renal prognosis, complications of malignancy, glucocorticoid (GC) toxicity, and mortality in immunoglobulin G4 (IgG4)-related kidney disease (IgG4-RKD).

Methods

Reviewing the medical records of 95 patients with IgG4-RKD, we investigated clinical and pathologic features at baseline, the course of renal function, complications of malignancy, GC toxicity, and mortality during follow-up (median 71 months). The standardized incidence ratio (SIR) of malignancy and standardized mortality ratio were calculated using national statistics. Factors related to outcomes were assessed by Cox regression analyses.

Results

At diagnosis, the median estimated glomerular infiltration rate (eGFR) was 46 ml/min per 1.73 m2. GC achieved initial improvement. Additional renal function recovery within 3-months of initial treatment occurred in patients with highly elevated serum IgG and IgG4 levels and hypocomplementemia. During follow-up, 68%, 17%, and 3% of the patients had chronic kidney disease (CKD), >30% eGFR decline, and end-stage renal disease (ESRD), respectively. Age-adjusted and sex-adjusted Cox regression analyses indicated that eGFR (hazard ratio [HR], 0.71) and extensive fibrosis (HR, 2.58) at treatment initiation had a significant impact on the time to CKD. Ten patients died, and the standardized mortality ratio was 0.94. The SIR of malignancy was 1.52. The incidence rate (IR) of severe infection was 1.80/100 person-years. Cox regression analyses showed that the best eGFR within 3 months after treatment initiation were associated with lower mortality (HR 0.67) and fewer severe infections (HR 0.63).

Conclusion

This study suggests that more renal function recovery through early treatment initiation may improve patient survival, renal outcomes, and some GC-related complications in IgG4-RKD.

Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation

A diverse spectrum of pathologically distinct, nonneoplastic, proliferative conditions of the kidneys and urinary tract demonstrate a expansile growth pattern similar to that of neoplasms. The renal pseudotumors include myriad causes of infections as well as rare noninfectious causes such as sarcoidosis, amyloidosis, and immunoglobulin G4-related disease (IgG4-RD). Rare entities such as cystitis cystica, endometriosis, nephrogenic adenoma, and pseudosarcomatous myofibroblastic proliferation and distinct types of prostatitis comprise tumefactive nontumorous disorders that affect specific segments of the urinary tract. The pseudotumors of the kidneys and urinary tract demonstrate characteristic histopathologic and epidemiologic features, as well as protean clinical manifestations, natural history, and imaging findings. Many patients present with genitourinary tract-specific symptoms or systemic disease. Some cases may be incidentally discovered at imaging. Some entities such as perinephric myxoid pseudotumors, IgG4-RD, fibroepithelial polyp, and nephrogenic adenoma display specific anatomic localization and disease distribution. Imaging features of multisystem disorders such as tuberculosis, sarcoidosis, and IgG4-RD provide supportive evidence that may allow precise diagnosis. Fungal pyelonephritis, xanthogranulomatous pyelonephritis, IgG4-RD, actinomycosis, and endometriosis show markedly low signal intensity on T2-weighted MR images. Although some pseudotumors exhibit characteristic imaging findings that permit correct diagnosis, laboratory correlation and histopathologic confirmation are required for definitive characterization in most cases. A high index of suspicion is a prerequisite for diagnosis. Accurate diagnosis is critical for instituting optimal management while preventing use of inappropriate therapies or interventions. Surveillance CT and MRI are frequently used for monitoring the response of pseudotumors to therapy. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

MRI diagnosis of tumor‑like IgG4 masses in bilateral distal ureters: A case report

IgG4 masses in the bilateral distal ureters are rare and frequently misdiagnosed. The present study reported the case of a 55-year-old male patient with IgG4-related disease (IgG4-RD) who had symmetrical soft tissue masses of the bilateral distal ureters found on magnetic resonance imaging (MRI) with a significant increase in the serum levels of IL-6, IgG4 and IgE. Regarding treatment, this patient received prednisone acetate tablets (40 mg/day) and mycophenolate mofetil dispersible tablets (1 g/day). During the follow-up, significant reductions in the levels of IgG4 and IgE were found after 30 days. MRI after 6 months indicated complete disappearance of the masses. The prognosis has been good so far. In clinical practice, it is necessary to consider the possibility of IgG4-RD in cases with soft tissue masses surrounding both ureters and elevated levels of serum IgG4.

A case of ureteral stenosis due to ureteritis probably associated with rheumatoid arthritis

Ureteritis associated with the immunological disorder is rarely reported, and most cases in this category are small vessel vasculitis and immunoglobulin G4-related disease. Rheumatoid arthritis (RA)-associated ureteritis is uncommon, and underlying aetiology is unclear. We present a patient with ureteritis who had a medical history of RA and was successfully treated with steroids and immunosuppressant. A 49-year-old woman who had been treated for RA and atopic dermatitis suffered from gross haematuria for 5 successive days. Contrast-enhanced computed tomography (CT) showed right-dominant upper urinary tract dilatation with enhanced thickened wall. The haematuria continued accompanied with intermittent right back and lower abdominal pain, and the following CT image taken after 3 months presented the progression to bilateral hydronephrosis. Ureteral stents were placed, and antibiotic therapy was introduced for obstructive pyelonephritis. Ureterocystoscopy and following biopsy from the upper ureteral tract showed a chronic inflammatory change in the histopathology, and we finally considered the stenosing ureteritis to be caused by immune-mediated mechanism related to RA. After starting steroid therapy with methotrexate, therapeutic response was obtained to remove the stents. In the cases of ureteritis or ureteral stenosis of unknown aetiology with a medical history of immunological disorders, we should consider the underlying immune-activated state and try to test contrast-enhanced CT and histological examination before performing a surgical procedure. After excluding the common causes of ureteritis or ureteral stenosis, these tests would support the appropriate diagnosis.

Reshaping the Concept of Riedel's Thyroiditis into the Larger Frame of IgG4-Related Disease (Spectrum of IgG4-Related Thyroid Disease)

Recently, Riedel's thyroiditis (RT) was assimilated into the larger spectrum of immunoglobulin IgG4-related disease (IgG4-RD) in addition to a particular frame of IgG4-related thyroid disease (IgG4-RTD), underlying IgG4-RT, IgG4-associated Hashimoto's thyroiditis (and its fibrotic variant), and IgG4-related Graves's disease. Our objective was to overview recent data on RT, particularly IgG4-RD and IgG4-RTD. The case and study- sample analysis (2019-2023) included 293 articles and selected 18 original studies: nine single case reports (N = 9, female/male = 2/1, aged: 34-79 years, 5/9 patients with serum IgG4 available data, 2/5 with high serum IgG4) and four case series (N = 21; 4/5 series provided data on IgG4 profile, 3/21 had serum IgG4 assays, and 2/3 had abnormally high values). IgG4-RD and thyroid findings were analyzed in three cohorts (N = 25). Another two studies (N = 11) specifically addressed IgG4-RTD components. On presentation, the patients may have hypothyroidism, transitory thyrotoxicosis, goiter, long-term history of positive anti-thyroid antibodies, and hypoechoic ultrasound thyroid pattern. The 5-year analysis (N = 66) showed the rate of serum IgG4 evaluation remained low; normal values do not exclude RT. Mandatory histological and immunohistochemistry reports point out a high content of IgG4-carrying plasma cells and IgG4/IgG ratio. Unless clinically evident, histological confirmation provides a prompt indication of starting corticoid therapy since this is the first-line option. Surgery, if feasible, is selective (non-responders to medical therapy, emergency tracheal intervention, and open/core needle biopsy). Current open issues are identifying the role of serum IgG4 assays in patients with IgG4-RD, finding out if all cases of RT are IgG4-mediated, applying IgG4-RTD criteria of differentiation among four entities, and providing an RT/IgG4-RTD guideline from diagnosis to therapy. It remains that the central aim of approaching RT in daily practice is the early index of suspicion in order to select patients referred for further procedures that provide enough histological/immunohistochemistry material to confirm RT and its high IgG4 burden.

IgG4-related kidney disease complicated with retroperitoneal fibrosis: A case report

BACKGROUND

IgG4-related disease (IgG4-RD) is a chronic fibrotic disease mediated by immunity recognized by clinicians in recent years. When the kidney is involved, it is called IgG4-related kidney disease (IgG4-RKD). IgG4-related tubulointerstitial nephritis (IgG4-TIN) is a representative manifestation of IgG4-RKD. IgG4-TIN can cause obstructive nephropathy complicated by retroperitoneal fibrosis (RPF). Cases of IgG4-TIN complicated with RPF are rare. Glucocorticoids are the first-line therapeutic medication for IgG4-RD and can significantly improve renal function.

CASE SUMMARY

Herein, we report the case of a 56-year-old man with IgG4-RKD complicated with RPF. The patient presented to the hospital with complaints of elevated serum creatinine (Cr), nausea, and vomiting. During hospitalization, Cr was 1448.6 µmol/L, and serum IgG4 was increased. A total abdominal computed tomography (CT) scan and enhanced CT scan obviously indicated RPF. Although this patient had a long course and renal insufficiency, we performed a kidney biopsy. Renal biopsy showed that the renal tubulointerstitium had focal plasma cell infiltration and increased lymphocyte infiltration accompanied by fibrosis. After combining the biopsy results with immunohistochemistry, it was found that the absolute number of positive IgG4+ cells per high power field exceeded 10, and the ratio of IgG4/IgG was over 40%. Finally, the patient was diagnosed with IgG4-TIN complicated with RPF and given glucocorticoids as long-term maintenance therapy, helping him keep out of dialysis. After a follow-up of 19 mo, the patient had recovered well. Previous literature on IgG4-RKD and RPF was retrieved from PubMed to characterize the clinical and pathological features and to identify the diagnosis and treatment of IgG4-RKD.

CONCLUSION

Our case report demonstrates the clinical characteristics of IgG4-RKD complicated with RPF. Serum IgG4 is a favorable indicator for screening. Performing renal biopsy actively plays a vital role in diagnosis and treatment, even if the patient has a long course and manifests with renal insufficiency. It is remarkable to treat IgG4-RKD with glucocorticoids. Hence, early diagnosis and targeted therapy are essential for reversing renal function and improving extrarenal manifestations in patients with IgG4-RKD.

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.

Successful therapy of retroperitoneal fibrosis due to IgG4-related disease with rituximab, cyclophosphamide and glucocorticoids followed by maintenance therapy wit ritutixmab

Idiopathic retroperitoneal fibrosis (IRF) is a rare condition characterized by the development of a peri-aortic and peri-iliac tissue showing chronic inflammatory infiltrates and pronounced fibrosis. Ureteral entrapment with consequent obstructive uropathy is one of the most common complications, which can lead to acute renal failure and, in the long term, to varying degrees of chronic kidney disease. Common symptoms at onset include lower back, abdominal or flank pain, and constitutional symptoms such as malaise, fever, and anorexia and weight loss. Pain is frequently referred to the hip, to the groin and to the lateral regions of the leg, with nocturnal exacerbations, and typically does not modify with position. We report a case of 56 year-old male with recurrent lower back pain and lower abdominal pain. Contrast-enhanced computed tomography and was suggestive of retroperitoneal fibrosis and unilateral ureteral occlusion. Histologic examination with immunohistochemical staining for IgG4 demonstrate IgG4-related retroperitoneal fibrosis. Therapy was started with prednison 1 mg/kg, but the tolerance of this dose was poor. Therefore the therapy was switched to combination of rituximab 375 mg/ m2 on day 1, cyclophosphamide 300 mg/m2 mg infusion and dexamethasone 20 mg total dose infusion on day 1 and 15 in 28 days cycle. FDG-PET/CT control in fourth month showed residual accumulation of FDG in retroperitoneal fibrotic mass, and therefore the therapy was prolonged to 8 month. The subjective symptoms of this diseases disappeared in the 8th month. Then the maintenance therapy, administration of rituximab in 6 month interval, was started. The activity of this disease be further evaluated by FDG-PET/CT imagination. Glucocorticoids are considered the cornerstone of therapy. The use of other immunosuppressive agents, including cyclophosphamide, azathioprine, methotrexate, mycophenolate mofetil and biological agents such as rituximab, tocilizumab and infliximab and sirolimus have been reported as a valuable option mostly in case reports, cases series and small studies. This agents allowed to reduce cumulative dose of glucocorticoids and its adverse effects. Therefore in our patients we preferred combination of rituximab cyclophosphamide s dexamethasone with lover dose of prednisonem. This combination is preferable for patients who cannot tolerate glucocorticoids or who are likely to suffer from significant glucocorticoids -related toxicity.

Advantages of an alternate-day glucocorticoid treatment strategy for the treatment of IgG4-related disease: A preliminary retrospective cohort study

Alternate-day glucocorticoid (GC) therapy is a treatment option that can reduce GC-associated adverse events. We investigated the safety and efficacy of alternate-day GC therapy in patients with immunoglobulin G4-related disease (IgG4-RD). Medical records of patients with IgG4-RD who were followed for at least one year at St. Luke's International Hospital, Tokyo, Japan, from 2004 to 2020 were reviewed. Patients who fulfilled comprehensive IgG4-RD diagnostic criteria were divided into alternate-day or daily GC treatment groups based on their treatment protocol. The effect of alternate-day GC therapy on glucocorticoid toxicity index (GTI) score was evaluated using multilinear analysis with adjustments for cumulative GC doses until each assessment point and propensity scores (PS) for alternate-day GC therapy. Kaplan-Meier curves and Cox proportional hazard models were used to assess the efficacy of alternate-day GC therapy for disease control. Among the 67 patients with IgG4-RD, patients with alternate-day (n = 13) and daily (n = 31) GC treatments were analyzed after excluding 23 ineligible patients. The median (interquartile range) age was 64 (60-70) years, 29 (65.9%) were male patients, 26 (59.1%) patients had positive biopsy results, and the median follow-up period was 1643 days. Significantly more patients with alternate-day GC treatment used concomitant immunosuppressants (11 [84.6%] vs 11 [35.5%]; P = .007). The alternate-day strategy significantly lowered the GTI score after adjusting for cumulative GC dose until the assessment and PS (adjusted coefficient: -29.5 [-54.3, -4.8], P = .021 at 12 months; -20.0 [-39.8, -0.1], P = .049 at 24 months). Serious infections were numerically less frequent in the alternate-day group (incidence ratio [95% confidence interval [CI]: 0.45 [0.05, 3.63], P = .45). Most patients (92.3%) in the alternate-day GC treatment group and all patients in the daily GC treatment group showed treatment responses in the remission induction therapy. The PS-adjusted hazard ratio of alternate-day GC treatment for disease flares was not significant (1.55 [0.53, 4.51]; P = .43). The alternate-day treatment strategy significantly reduced GC-related adverse events regardless of the cumulative GC dose. Alternate-day GC treatment is a feasible option for patients with IgG4-RD, without a significant increase in disease flares particularly when combined with immunosuppressants.

The contribution of the immune system to genitourinary fibrosis

Fibrotic diseases of the genitourinary tract are devastating and incompletely understood pathologies. These diseases include urethral and ureteral strictures, retroperitoneal fibrosis, and Peyronie's disease. They can contribute to obstructive uropathy and sexual dysfunction. Poor understanding of the pathophysiology of these diseases severely limits our ability to prevent and treat them. Genitourinary fibrotic diseases likely represent related pathologies that share common underlying mechanisms involving wound healing in response to injury. These diseases share the common feature of extracellular matrix abnormalities-such as collagen deposition, transforming growth factor-β accumulation, and dysregulation of collagen maturation-leading to abnormal tissue stiffness. Given the association of many of these diseases with autoimmunity, a systemic pro-inflammatory state likely contributes to their associated fibrogenesis. Herein, we explore the immunologic contribution to fibrogenesis in several fibrotic diseases of the genitourinary system. Better understanding how the immune system contributes to fibrosis in these diseases may improve prevention and therapeutic strategies and elucidate the functions of immunologic contributors to fibrosis in general.

Hematological Malignancies and the Kidney

The incidence of hematologic malignancies is on the rise worldwide. Kidney disease is ubiquitous in patients with hematologic malignancies, encompassing a wide spectrum of disorders involving each kidney compartment, including the vasculature, tubules, interstitium, and glomerulus, and there is significant overlap of kidney involvement with each hematologic malignancy. Vascular disorders include both microvascular and macrovascular damage, via thrombotic microangiopathy, hyperleukocytosis, hyperviscosity, and cryoglobulinemia. The tubulointerstitial compartment may be affected by prerenal azotemia and acute tubular injury, but malignant infiltration, tumor lysis syndrome, extramedullary hematopoiesis, cast nephropathy, granulomatous interstitial nephritis, and lysozymuria should be considered in certain populations. Obstructive uropathy may occur due to nephrolithiasis or retroperitoneal fibrosis. Glomerular disorders, including membranoproliferative, membranous, minimal change, and focal segmental glomerulosclerosis, can rarely occur. By understanding how each compartment may be affected, care can best be optimized for these patients. In this review, we summarize the widely varied etiologies of kidney diseases stratified by kidney compartment and hematologic malignancy, focusing on demographics, pathology, pathophysiology, mechanism, and outcomes. We conclude with common electrolyte abnormalities associated with hematologic malignancies.

Immunoglobulin G4-related Disease: A New Systemic Disease Emerging in Japan

Immunoglobulin G4-related disease (IgG4-RD) is a fibro-inflammatory disease characterized by organ enlargement and elevated serum IgG4 levels. In 2003, IgG4-RD was proposed as a distinct form of IgG4-related systemic disease based on a histopathological study involving patients with autoimmune pancreatitis. IgG4-RD occurs mainly in older men and can affect almost any organ simultaneously or metachronously. Pathophysiologically, IgG4-RD occurs when an autoantigen triggers an immune response characterized by Th2 predominance with increased production of cytokines, such as interleukin 4 (IL-4), IL-5, IL-10, IL-13, and tumor growth factor-β (TGF-β), in the affected organ. IL-10 and TGF-β produced by the increased number of regulatory T cells induce a switch from B cells to IgG4-producing plasma cells and fibrosis, respectively. The characteristic histological features consist of dense infiltration of lymphocytes and IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis. IgG4-RD is diagnosed based on a combination of clinical, serological, radiological, and histopathological findings. Differentiating IgG4-RD from malignant tumors or similar inflammatory diseases in the affected organs is important. The 2019 America College of Rheumatology/European League against Rheumatism classification criteria for IgG4-RD have high diagnostic sensitivity and specificity. IgG4-RD generally responds well to treatment with steroids, and a swift response is reassuring and provides further diagnostic confirmation. However, relapses are common during tapering or after cessation of steroids. In Japan, low-dose steroid maintenance therapy is usually given to prevent a relapse. B-cell depletion with rituximab is effective in patients resistant to or dependent on steroids. Most patients with IgG4-RD who receive steroid therapy show good short-term clinical, morphological, and functional outcomes. However, long-term outcomes, such as relapse, fibrosis development, and associated malignancies, have not been clearly defined. Therefore, novel treatment strategies, including rituximab, need to be tested in international randomized controlled clinical trials.

Update on classification, diagnosis, and management of immunoglobulin G4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a newly recognized chronic fibro-inflammatory autoimmune disease, and its recognition has been constantly increasing worldwide over the last few years. A correct and timely recognition, as well as appropriate intervention, is crucial for the treatment of IgG4-RD. For certain subtypes of IgG4-RD, organ-specific criteria are formulated to make the diagnosis more accurate. New biomarkers have emerged in the recent years to aid the disease diagnosis, its prognosis prediction, as well as therapy response monitoring. Although recurrence is very common in IgG4-RD, glucocorticoid is still the first-line treatment for the majority of patients. The factors that affect the likelihood of disease relapse are multifaceted. The selection strategy of various steroid-sparing agents is still being explored. Besides, when patients have special sites involvement leading to severe clinical conditions, surgical operation or interventional therapy should also be considered. An update on classification, diagnosis, and management of IgG4-RD is provided in the current study to fully elucidate the recommended clinical practice of this mysterious disease.

Therapy of immunoglonuline IgG4 related disease (IgG4-RD)

Immunoglobulin IgG4 related disease (IgG4-RD) is a heterogeneous disorder with multi-organ involvement recognised as a separate entity at the beginning of this century only. Evolving therapy is reviewed in this paper. Glucocorticoids are first choice drug but long administration of glucocorticoids is connected with many adverse effects. In case of combination glucocorticoids and immunosuppressive agents lower doses of glucocorticoids are needed, the response rate is higher and therapy is better tolerated. Rituximab is drug, that is possible use as monotherapy or in combination with glucocorticoids and immunosuppressive drugs. Only one study compared two immunosuporessive drugs, mycophenolate mofetil and cyclophosphamide. The response rated was similar but remissions were longer after glucocorticoids with cyclophosphamide then glucocorticoids with mycofenolat mofetil. No other comparative study of combination of various imunossupressive drugs with glucocorticoids was published. Rituximab has high number (90 %) of response rate in monotherapy, but can be used in combination with glucocorticoids and immunosuppressives. Rituximab is now preferred and recommended for maintenance therapy administered in 6-month interval. In case of advanced disease, we prefer therefore combination of rituximab, cyclofosphamide and dexamethasone for initial therapy followed by maintenance with rituximab in 6 months interval. There are two new drugs under investigation abatacept and dupilimab with promising results. Although we have very intensive therapies for good results of therapy early diagnosis before irreversible fibrotic changes in IgG4-RD involved organs is still needed.

IgG4-related disease. Clinical manifestation differential diagnosis and recent International Diagnostic Criteria for IgG4-related disease

Immunoglobulin G4- related disease (IgG4-RD) is a rare systemic fibro-inflammatory disorder. Autoimmune pancreatitis is the most frequent manifestation of IgG4-RD. However, IgG4-RD can affect any organ such as salivary glands, orbits, retroperitoneum, prostate and many others. Recent research enabled a clear clinical and histopathological description of IgG4-RD and in 2019 four Clinical phenotypes of IgG4-related disease were described. Diagnosis is based on morphological examination with typical findings of lymphoplasmocellular inflammation, storiform fibrosis and obliterative phlebitis in IgG4-RD biopsies and the tissue invading plasma cells largely produce IgG4. Elevated serum IgG4 levels are found in many but not all patients. New diagnostic criteria for IgG4-RD have been published recently in 2019 and 2021. This review summarizes current knowledge on pathophysiology, clinical manifestations, diagnosis and differential diagnosis of IgG4-RD from the point of view 2022 and in next article brings overview of the IgG4-RD therapy.

IgG4-related tubulointerstitial nephritis

A 67-year-old man was referred to the renal team following an episode of acute kidney injury on a background of chronic kidney disease. He had a 9-year history of steroid-sensitive arthritis, epigastric pain and isolated submandibular gland enlargement. He was noted to have a raised eosinophil count, total serum protein and total immunoglobulin G4 (IgG4) level as well as a serum hypocomplementaemia. A renal biopsy showed a tubulointerstitial nephritis with lymphoplasmacytic infiltrates, fibrosis and IgG4-positive plasma cells on immunohistochemistry. A diagnosis of IgG4-related disease was made based on clinical presentation and pathology. Renal function improved with glucocorticoids and the patient was successfully transitioned to azathioprine as a steroid-sparing agent.

An Interesting Case of Immunoglobulin G4-Related Retroperitoneal Fibrosis Treated With Rituximab

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition. Its common manifestations include type I autoimmune pancreatitis and retroperitoneal fibrosis (RPF). We present a rare case involving a 43-year-old female who presented with left lower quadrant (LLQ) pain. Imaging of the abdomen and pelvis revealed left hydroureteronephrosis to the level of an inflammatory process in the left adnexal region, possibly reflecting a tubo-ovarian abscess (TOA). The gynecologic evaluation concluded that the mass was unlikely of gynecologic sources. Transgluteal biopsy of the mass was highly suggestive of IgG4-RD. The patient received prednisone and rituximab (RTX), resulting in complete resolution of the mass, which was confirmed on repeat imaging. This case report provides a valuable addition to the literature to highlight that the diagnosis of IgG4-RD is based on the combination of characteristic clinical, serologic, radiologic, and histopathologic findings. Also, it underlines that the management of the disease is through glucocorticoids (GCs) as the first-line agent for remission induction in all patients with active, untreated IgG4-RD. RTX therapy is an effective treatment for IgG4-RD that is refractory to GCs. Recent studies have suggested that RTX monotherapy can be used to induce and maintain remission in patients with IgG4-RD.

Immune Dysregulation in IgG4-Related Disease

Immunoglobin G₄-related disease (IgG₄-RD) is one of the newly discovered autoimmune diseases characterized by elevated serum IgG₄ concentrations and multi-organ fibrosis. Despite considerable research and recent advances in the identification of underlying immunological processes, the etiology of this disease is still not clear. Adaptive immune cells, including different types of T and B cells, and cytokines secreted by these cells play a vital role in the pathogenesis of IgG₄-RD. Antigen-presenting cells are stimulated by pathogens and, thus, contribute to the activation of naïve T cells and differentiation of different T cell subtypes, including helper T cells (Th1 and Th2), regulatory T cells, and T follicular helper cells. B cells are activated and transformed to plasma cells by T cell-secreted cytokines. Moreover, macrophages, and some important factors (TGF-β, etc.) promote target organ fibrosis. Understanding the role of these cells and cytokines implicated in the pathogenesis of IgG₄-RD will aid in developing strategies for future disease treatment and drug development. Here, we review the most recent insights on IgG₄-RD, focusing on immune dysregulation involved in the pathogenesis of this autoimmune condition.

IgG4-related Disease: a diagnostic challenge

Immunoglobulin IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition with a characteristic histopathological appearance that can affect almost any organ. The clinical features result from a focal or diffuse appearance of a tumor-like swelling of the affected organs, identified by physical and/or imaging examination. Herein, we report the case of a 38-year-old male complaining of a worsening chronic right lumbar pain associated with legs and scrotum edema. He also had itchy and erythematous cutaneous lesions on the abdominal wall over the last 8 months, and complained of a diffuse and mild to moderate abdominal discomfort. On examination, the liver was firmly enlarged and tender. His legs had 2+ symmetrical pitting edema extending from his feet to just above the knees. An abdominal computed tomography scan showed a large mass (10 x 8 x 4cm) involving the abdominal infrarenal aorta and the iliac arteries, and compressing the inferior vena cava, with dilated iliac veins, raising the possibility of lymphoproliferative disease. During the initial investigation, the laboratory workup revealed anemia, without other marked changes. A laparoscopic-guided biopsy of the peri-aortic mass was undertaken. The histological report associated with IgG4 immunoglobulin measurement rendered the diagnosis of IgG4-RD. The patient had a favorable outcome after the use of glucocorticoids with the abdominal mass remission.

The prevalence of extra-salivary gland complications in immunoglobulin G4-related sialadenitis

OBJECTIVES

To estimate the prevalence of extra-glandular lesions in patients with immunoglobulin G4-related sialadenitis (IgG4-RS).

METHODS

Six electronic databases (PubMed, EMBASE, Science Direct, Scopus, Web of Science, and China National Knowledge Infrastructure) were systematically searched from the date of inception of each database to March 2021. The Strengthening the Reporting of Observational Studies in Epidemiology statement was used to conduct methodological quality assessment, and a random-effect meta-analysis model was applied to estimate the prevalence. Publication bias was visually assessed using a funnel plot and calculated via Begg's and Egger's tests. The Stata 15 software was used to perform data analysis.

RESULTS

A total of 43 articles comprising 1,864 patients with IgG4-RS were considered to be eligible for this study. The pooled prevalence of extra-salivary gland lesions in IgG4-RS was 76.53% with a confidence interval (CI) of (69.39%, 83.04%). A higher prevalence was associated with studies published before or during 2015 (84.38%, CI [74.23%, 92.58%]) than those published after 2015 (68.55%, CI [58.44%, 77.88%]). Lacrimal gland involvement (54.68%, CI [45.61%, 63.60%]) and lymph node swelling (56.96%, CI [48.16%, 65.56%]) were the most frequent lesions.

CONCLUSIONS

Extra-glandular lesions were common in patients with IgG4-RS. More high-quality prospective studies with less heterogeneity are required to determine the accurate prevalence.

Disparities between IgG4-related kidney disease and extrarenal IgG4-related disease in a case-control study based on 450 patients

We aimed to compare the demographic, clinical and laboratory characteristics between IgG4-related kidney disease (IgG4-RKD+) and extrarenal IgG4-related disease (IgG4-RKD−) in a large Chinese cohort, as well as describing the radiological and pathological features of IgG4-RKD+. We retrospectively analyzed the medical records of 470 IgG4-related disease (IgG4-RD) patients at Peking University People’s Hospital from January 2004 to January 2020. The demographic, clinical, laboratory, radiological and pathological characteristics between IgG4-RKD+ and IgG4-RKD− were compared. Twenty IgG4-RD patients who had definite etiology of renal impairment including diabetes, hypertension and etc. were excluded. Among the remained 450 IgG4-RD patients, 53 were diagnosed with IgG4-RKD+ . IgG4-RKD+ patients had older age at onset and at diagnosis. Male to female ratio of IgG4-RKD+ patients is significantly higher. In the IgG4-RKD+ group, the most commonly involved organs were salivary gland, lymph nodes and pancreas. It was found that renal function was impaired in approximately 40% of IgG4-RKD+ patients. The most common imaging finding is multiple, often bilateral, hypodense lesions. Male sex, more than three organs involved, and low serum C3 level were risk factors for IgG4-RKD+ in IgG4-RD patients. These findings indicate potential differences in pathogenesis of these two phenotypes.

IgG4-related disease with multiorgan involvement: a case-based review

IgG4-related disease (IgG4-RD) is an immune-mediated multi-organ inflammatory disorder caused by tissue infiltration of lymphocytes with IgG4-secreting plasma cells. Herein, we discuss a case of a patient with IgG4-RD who had involvement of multiple organs: the kidneys, lymph nodes, bone marrow (biopsy performed), lungs, liver, and small intestine (imaging abnormalities). Although several case reports and series of IgG4-RD involving different organ involvement are in the literature, our patient has extensive simultaneous multi-organ involvement. We utilized the four domains (serologic, pathologic, radiologic, and pathologic) as discussed in the new 2019 ACR/EULAR classification criteria to provide a useful framework in considering an alternative tool for IgG4-RD in multi-organ involvement, where biopsy is more invasive and not always accessible. We highlight the findings of each organ involved that increase the likelihood that the patient has IgG4-RD. In our patient, the IgG4-RD classification criteria was fulfilled with total points adding up to 48. Our case meets the classification criteria for IgG4-RD, since at least one organ is involved to meet entry criteria (biopsy proven), no exclusion criteria are present, and the total points are ≥ 20. When such extensive involvement of IgG4-RD occurs, early diagnosis and treatment are recommended to avoid irreversible organ damage and better outcomes.

Tertiary lymphoid tissue in early-stage IgG4-related tubulointerstitial nephritis incidentally detected with a tumor lesion of the ureteropelvic junction: a case report

Background

IgG4-related kidney disease causes renal impairment of unknown pathogenesis that may progress to kidney failure. Although ectopic germinal centers contribute to the pathogenesis of the head and neck lesions of IgG4-related disease, the presence of tertiary lymphoid tissue (TLT) containing germinal centers in IgG4-RKD has rarely been reported.

Case presentation

We report a 72-year-old Japanese man who had IgG4-related tubulointerstitial nephritis (TIN) with TLT formation incidentally detected in a resected kidney with mass lesion of IgG4-related ureteritis in the ureteropelvic junction. During follow-up for past surgical resection of a bladder tumor, renal dysfunction developed and a ureter mass was found in the right ureteropelvic junction, which was treated by nephroureterectomy after chemotherapy. Pathology revealed no malignancy but abundant IgG4-positive cell infiltration, obliterative phlebitis and storiform fibrosis, confirming the diagnosis of IgG4-related ureteritis. In the resected right kidney, lymphoplasmacytes infiltrated the interstitium with focal distribution in the renal subcapsule and around medium vessels without storiform fibrosis, suggesting the very early stage of IgG4-TIN. Lymphocyte aggregates were also detected at these sites and consisted of B, T, and follicular dendritic cells, indicating TLT formation. IgG4-positive cells infiltrated around TLTs.

Conclusions

Our case suggests that TLT formation is related with the development of IgG4-TIN and our analysis of distribution of TLT have possibility to elucidate IgG4-TIN pathophysiology.

Immunoglobulin G-4-Related Retroperitoneal Fibrosis

Retroperitoneal fibrosis is caused by the replacement of normal retroperitoneal tissue with fibrosis. The majority of the cases are idiopathic, but some secondary causes include malignancy, infection, drugs, and radiotherapy. Immunoglobulin G-4 (IgG-4) related disease is a relatively newer disease and one of the rarer causes of retroperitoneal fibrosis. It usually involves the pancreas, lungs, kidneys, aorta lacrimal and salivary glands, or extrapancreatic bile duct. Elevated serum IgG-4 is the biomarker of the disease and its levels correlate with disease activity. High-dose glucocorticoid is the treatment of choice.

Prognostic factors in IgG4-related disease: a long-term monocentric Chinese cohort study

OBJECTIVES

Patients with IgG4-related disease (IgG4-RD) suffer high relapse rates during long-term treatment, but factors that predict relapse outcomes are not well established. In the present study, we aimed to identify predictive factors for treatment resistance and disease relapse in a Chinese IgG4-RD cohort.

METHODS

This study enrolled 102 patients newly diagnosed with IgG4-RD. Disease prognosis was determined by evaluating disease activity and dosage of glucocorticoids. Predictive factors for refractory and relapsed disease were identified by univariate analysis and Cox regression.

RESULTS

Among the 102 patients, 78 cases received medical treatment with regular follow-up (21 [6-111] months). During the follow-up period, 55 (70.5%) patients sustained clinical remission, and 23 (29.5%) patients suffered refractory or relapsed disease. The relapse rate of the patients with IgG4-RD was significantly higher among patients who stopped taking medicine than among those who continued treatment with glucocorticoids (GC) + immunosuppressor (IM). Serum TNF-α ≥ 13 pg/mL, sIL-2R ≥ 1010 U/mL, total cholesterol < 3.55 mmol/L, low-density lipoprotein < 2.0 mmol/L, IgG ≥ 20.2 g/L, and drug withdrawal were predictive factors for refractory and relapsed IgG4-RD. Multivariate Cox regression revealed that both sIL-2R and TNF-α were independent risk factors for refractory and relapsed disease. The combination of GC and IM treatment was an independent protective factor against refractory and relapsed IgG4-RD.

CONCLUSIONS

High serum levels of sIL-2R and TNF-α may be informative risk factors for refractory and relapsed IgG4-RD. Our data suggest that a combination treatment of GC along with IM may be protective against refractory and relapsed IgG4-RD. Key Points • High sIL-2R and TNF-α levels are informative risk factors for refractory and relapsed IgG4-related disease. • Combination treatment of GC with IM protects against refractory and relapsed IgG4-related disease.

Immunoglobulin G4-related Disease of the Genitourinary System: Spectrum of Imaging Findings and Clinical-Pathologic Features

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disease characterized by focal or diffuse organ infiltration of IgG4-bearing plasma cells. The diagnosis of IgG4-RD is based on a combination of clinical, serologic, radiologic, and histopathologic findings. IgG4-RD has been reported to affect almost all organ systems. The kidney is the most frequently involved of the genitourinary organs. The most common renal manifestation of IgG4-RD is IgG4-RD tubulointerstitial nephritis, followed by membranous glomerulonephropathy and, less frequently, obstructive nephropathy involving the renal pelvis, ureter, or retroperitoneum. Renal parenchymal lesions may appear as multiple nodular lesions, diffuse patchy infiltrative lesions, or a single nodular lesion. Multiple small nodular cortical lesions are the most common imaging findings of IgG4-RD involving the kidney. Renal pelvic, sinus, or perinephric lesions can also occur. IgG4-RD involvement of other genitourinary organs including the ureter, bladder, urethra, and male and female reproductive organs is rare compared with kidney involvement but may show variable imaging findings such as a localized mass within or surrounding the involved organ or diffuse enlargement of the involved organ. Imaging findings of IgG4-RD involving the genitourinary system are nonspecific but should be differentiated from inflammatory and neoplastic lesions that mimic IgG4-RD. The online slide presentation from the RSNA Annual Meeting is available for this article. ^©RSNA, 2020.

A challenging case report of IgG4-related systemic disease involving the heart and retroperitoneum with a literature review of similar heart lesions

The IgG4-related disease is a distinct, steroid-responsive fibro-inflammatory disorder of unknown etiology. This multiorgan disease is characterized by tumefactive lesions that contain rich infiltrations of IgG4-positive plasma cells, with the pancreas, and the salivary and lacrimal glands being the main involved. The more common cardiovascular involvements include inflammatory peri-aortitis, coronary arteritis, and pericarditis. Intra-cardiac tumefactive lesions are rarely reported. Herein, we describe a challenging case of IgG4-related disease with a long-time lag between initiation of symptoms to proper diagnosis with biopsy-proven cardiac and retroperitoneal and possible pituitary gland involvement. Concerning the rarity of the cardiac lesion in our case, we conducted a literature review of similar case reports.

Clinical phenotypes of IgG4-related disease reflect different prognostic outcomes

Introduction

Four clinical phenotypes of IgG4-related disease (IgG4-RD) have been recently identified by latent class analysis (LCA): pancreato-biliary (group 1); retroperitoneum/aortitis (group 2); head and neck limited (group 3); and Mikulicz/systemic (group 4). The reproducibility of this classification in clinical practice and its relevance for patient management, however, remain unknown.

Methods

The study included 179 patients. Four IgG4-RD experts were asked to classify a validation cohort of 40 patients according to published LCA-derived phenotypes based on clinical judgement. Agreement between LCA and clinical clustering was calculated. To assess differences among disease phenotypes, the following variables were recorded on an additional 139 patients: serum IgG4 and IgE; inflammatory markers; eosinophils; plasmablasts; IgG4-RD responder index (RI); history of atopy, diabetes, osteoporosis, relapses and malignancy; cumulative dose of glucocorticoids; and use of rituximab.

Results

Clinical judgement replicated LCA classification with strong agreement among IgG4-RD experts (κ = 0.841, P &lt; 0.0005). At disease onset, group 1 showed the highest levels of serum IgG4 and IgE. Groups 2 and 4 had the lowest and highest IgG4-RD RI, respectively. At 2 years’ follow-up, group 3 received the highest cumulative dose of glucocorticoids, but higher incidences of diabetes mellitus were observed in groups 1 and 4, consistent with the higher likelihood of pancreatic involvement in groups 1 and 4. No difference among the four groups was observed in terms of disease recurrence, time to relapse and frequency of rituximab infusion.

Conclusion

Clinical phenotypes of IgG4-RD reflect differences in epidemiological features and prognostic outcomes.

IgG4-related disease mimicking renal pelvis tumor with peritoneal carcinomatosis

IgG4-RD may rarely present as a retroperitoneal fibrosis, mimicking carcinomatosis. Clinicians should consider this disease when encountering an idiopathic peritoneal and retroperitoneal fibrosis with renal involvement and hydronephrosis.

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.

IgG4-related disease: a clinical perspective

IgG4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory disorder that can affect almost any organ. Common presentations include major salivary and lacrimal gland enlargement, orbital disease, autoimmune pancreatitis, retroperitoneal fibrosis and tubulointerstitial nephritis. The main histopathological features are a dense, polyclonal, lymphoplasmacytic infiltrate rich in IgG4+ plasma cells, storiform fibrosis and obliterative phlebitis. The precise pathogenic mechanisms of IgG4-RD are still unclear. CD4+ T and B cells, including IgG4-expressing plasmablasts, constitute the major inflammatory cell populations and are believed to cause organ damage and tissue fibrosis. The diagnosis of the disease may be challenging and should be based on specific histopathological findings, typical laboratory and radiological aspects and an appropriate clinical context. The first-line treatment of IgG4-RD is based on glucocorticoids, which are usually efficacious. However, B cell depletion induced by rituximab has also been found to induce remission in steroid-resistant disease or has been used as steroid-sparing agent for relapsing disease. This review provides an update on clinical and therapeutic aspects of IgG4-RD.

Case report: IgG4-related renal disease co-existing with retroperitoneal fibrosis

A 51-year-old woman visited our clinic for orthopnea, chest discomfort, and facial and leg edema. Acute kidney injury and pleural effusion were diagnosed and she received hemodialysis. This is a rare case of IgG4-related disease diagnosed by renal biopsy in the patient with retroperitoneal fibrosis and severe acute kidney injury, which progressed rapidly and required hemodialysis without markedly elevated serum IgG4 level and urinary tract obstruction. Immunostaining of a kidney biopsy revealed IgG4-related renal disease and magnetic resonance imaging showed retroperitoneal fibrosis in the paraspinal and presacral areas. After 3 days of glucocorticoid treatment, renal function and bilateral pleural effusion were restored. Another 2 months of glucocorticoid treatment decreased the extent of retroperitoneal fibrosis on follow-up abdominal computed tomography. IgG4-related disease is a recently recognized fibro-inflammatory condition with a dense lymphoplasmacytic infiltration of IgG4-positive plasma cells. The kidney and retroperitoneum are the frequently associated organs in IgG4-related disease. This case shows that IgG4-related disease can involve the kidney and/or other organs and be diagnosed by kidney biopsy.