IgG4-related disease of the ureter: report of two cases and review of the literature

Renal Manifestations of IgG4-Related Disease: A Concise Review

IgG4-related disease (IgG4-RD) is an immune-mediated disorder marked by fibro-inflammatory masses that can infiltrate multiple organ systems. Due to its relatively recent discovery and limited understanding of its pathophysiology, IgG4-related disease may be difficult to recognize and is consequently potentially underdiagnosed. Renal involvement is becoming regarded as one of the key features of this disease. To date, the most well-recognized renal complication of IgG4-related disease is tubulointerstitial nephritis, but membranous glomerulonephritis, renal masses, and retroperitoneal fibrosis have also been reported. This concise review has two objectives. First, it will briefly encapsulate the history, epidemiology, and presentation of IgG4-related disease. Second, it will examine the reported renal manifestations of IgG4-related disease, exploring the relevant histology, imaging, clinical features, and treatment considerations. This synthesis will be highly relevant for nephrologists, rheumatologists, general internists, and renal pathologists to raise awareness and help improve early recognition of IgG4-related kidney disease (IgG4-RKD).

Erdheim‑Chester disease of multisystem involvement with delayed diagnosis: A case report and literature review

Erdheim-Chester disease (ECD) is a rare tumor of histiocytic origin, characterized by foamy or lipid-laden histiocytes mixed or surrounded by fibrosis that infiltrate multiple organs. Misdiagnosis is common due to the diversity of clinical presentations. The present study reported a case of ECD with the involvements of bone, cardiac, aorta and retroperitoneum. The patient had no obvious clinical symptoms and no noteworthy foamy histiocytes or Touton giant cells were found on pathological examination, delaying the diagnosis. The patient was a young male found to have pericardial effusion on physical examination, and computed tomography (CT) revealed soft tissue infiltrates in the retroperitoneum and around the aorta. A mediastinal biopsy revealed fibrous connective tissue with small-vessel hyperplasia and acute-chronic inflammatory cell infiltration. The initial diagnosis was retroperitoneal fibrosis (RPF), and hormonal and tamoxifen treatments were administered. The patient presented with oliguria, eyelid edema and fever four years later. A repeat CT revealed an increase in the extent of tissue infiltration and pericardial effusion compared with the previous CT. Subsequent cardiac magnetic resonance imaging revealed massive thickening in the form of fibrotic tissue infiltrating the heart and surrounding thoracic and abdominal aorta. Single photon emission CT revealed multiple areas of increased bone metabolism, particularly symmetrical involvement of the long bones of both lower extremities. A biopsy of the perirenal tissue revealed fibrous tissue and a small number of lymphocytes and macrophages [typical foamy histiocytes observed via x200 magnification and hematoxylin-eosin (HE) staining, no presence of xanthogranuloma or Touton giant cells]. After a comprehensive evaluation and ruling out other diseases, the diagnosis of ECD was determined. The prognosis of this disease is poor; early diagnosis is critical and requires accurate judgment by clinicians. Biopsies of all involved sites and refinement of genetic tests to guide treatment, if possible, are both necessary.

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.

A case of IgG4-related interstitial nephritis with ureteral obstruction: case report and literature review

BACKGROUND

IgG4-related disease (IgG4-RD) is a newly discovered systemic disease that can affect any organ or tissue in the body. IgG4-related kidney disease (IgG4-RKD) is relatively rare but essential to IgG4-RD. However, there are few reports of IgG4-RD mimicking malignant ureteral tumors leading to hydronephrosis. We report here a rare case of IgG4-RD involving the ureter.

CASE PRESENTATION

An 87-year-old man presented to our nephrology department with anorexia, nausea, and acute kidney injury in November 2020. Urinary computed tomography (CT) examination revealed a right lower ureter mass with right renal and ureter hydronephrosis. The serum level of IgG4 was 1890 mg/dL, and the concurrently renal biopsy revealed extensive infiltration of IgG4-positive plasma cells in renal interstitium, which was diagnosed as IgG4-associated tubule-interstitial nephritis(IgG4-TIN). The renal function improved significantly after double-J tube implantation of the right ureter and moderate-dose hormone therapy. The serum IgG4 decreased to the normal range, and the right lower ureter mass almost disappeared after one year of low-dose hormone maintenance therapy.

CONCLUSION

IgG4-RD can present as a mass in the renal pelvis and (or) ureter, leading to hydronephrosis. Therefore, early recognition of this disease is significant. Most patients respond well to hormonal therapy to avoid surgical treatment due to misdiagnosis as malignant tumors, causing secondary harm to patients.

Histopathologic and clinical comparison of recurrent and non-recurrent urethral stricture disease treated by reconstructive surgery

Background

Urethral stricture is a relatively frequent problem often requiring multiple surgical interventions. The objective of this study was to compare the clinicopathologic features of urethral resections from patients who underwent open end-to-end anastomotic urethroplasty and later recurred compared to those who did not.

Methods

A retrospective review of the pathology files identified 36 consecutive patients who underwent urethroplasty. The histopathological analysis included evaluation of the inflammatory infiltrate based on the predominant (>50%) cell type: lymphocyte-rich, neutrophil-rich, plasma cell-rich, and mixed; length and thickness of the fibrous plaque; and the cellularity of the fibrous plaque: cellular (>40 stroma nuclei/HPF) or paucicellular (<40 stroma nuclei/high power field).

Results

Ten (28%) patients recurred, and 26 (72%) did not. There was no significant difference between recurrent and non-recurrent cases in age, race, comorbidities, location of the stricture, and etiology. All patients with recurrent strictures showed dense paucicellular fibrotic plaques (10/10; 100%), while this was seen in 14/26 (53.8%) non-recurrent cases (P=0.01). Only one patient with cellular fibrosis showed recurrence during follow-up. The log-rank test shows that time to recurrence is significantly shorter in patients with paucicellular fibrosis compared to those with cellular fibrosis (P=0.036). The inflammation consisted of a mixed population of CD3(+) T-lymphocytes, CD20(+) B-lymphocytes, and CD68(+) histiocytes, and there was no difference in the composition of the inflammation between groups. All cases with plasma cell-rich infiltrate showed normal IgG4:IgG.

Conclusions

Our study supports reporting cellularity of the fibrous plaque as a potential predictor of outcome in patients undergoing reconstructive urethroplasty. Patients with paucicellular fibrosis are at increased risk of recurrence.

Peri-ureteric mass an unusual case of immunoglobin G4-related disease (IgG4-RD)

Immunoglobulin G4-related disease (IgG4-RD) of the ureter is a rarely reported disease, often mimicking urothelial carcinoma. This paper describes a case of an otherwise healthy patient with a lesion involving the ureter revealed on Computed tomography (CT), avid on fludeoxyglucose positron emission tomography (FDG PET), that prior to surgery was suspicious for urothelial carcinoma, until intra-op frozen section revealed otherwise. Diagnosis of ureteral IgG4-RD should be considered as a differential diagnosis, with serum IgG4 levels obtained.

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.

IgG4-related focal retroperitoneal fibrosis in ureter suggestive of colon cancer recurrence and resected laparoscopically: a case report

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a novel disease concept of unknown cause that is characterized by abundant infiltration of IgG4-positive cells, mass-forming lesions, and elevated serum IgG4 levels. The infiltration of IgG4-positive plasma cells and lymphocytes causes swelling, inflammation, fibrosis, and obliterative phlebitis in multiple organs. On the other hand, IgG4-RD occurring in the ureters has rarely been reported. To our knowledge, this is the first report of laparoscopic partial ureteral resection for IgG4-related focal retroperitoneal fibrosis in a ureter with suspected colon cancer recurrence.

CASE PRESENTATION

A 72-year-old man with a history of sigmoid colon cancer visited Shiga University of Medical Science Hospital for regular follow-up in December 2019. Enhanced abdominal computed tomography revealed a mass involving the left ureter. Furthermore, fluorine-18 fluorodeoxyglucose positron emission tomography showed significant accumulation of fluorodeoxyglucose uptake in the same region. Due to the possibility of colon cancer recurrence, a laparoscopic excisional biopsy with partial ureteral resection was performed. Histologically, IgG4-positive plasma cell infiltration exceeding 10 cells per high-power field and a high ratio of IgG4-positive/IgG-positive cells exceeding 40% were observed. The postoperative serum IgG4 level was 384 mg/dL. With the application of these findings to the diagnostic algorithm in the comprehensive diagnostic criteria for IgG4-RD, the mass-forming lesion was diagnosed as definitive IgG4-related focal retroperitoneal fibrosis.

CONCLUSIONS

IgG4-RD should be considered in the differential diagnosis of retroperitoneal lesions. Moreover, laparoscopic surgery may be useful for making the diagnosis in difficult-to-biopsy cases.

Urinary System Manifestation of IgG4-Related Disease: Clinical, Laboratory, Radiological, and Pathological Spectra of a Chinese Single-Centre Study

Background

IgG4-related disease is a new disease entity, but little attention was drawn to urinary system involvement besides nephritis or nephropathy. Here, we described clinical, radiological, and pathological manifestations of IgG4-related urinary disease (IgG4-RUD) and assess its treatment responses.

Methods

We conducted a retrospective study enrolling 65 IgG4-RUD patients from an IgG4-related disease (IgG4-RD) cohort of the Peking Union Medical College Hospital. Clinical, laboratory, radiological, pathological data were collected, and treatment response to immunosuppressants were analysed.

Results

IgG4-related interstitial nephritis (TIN, 32.3%), glomerular nephritis (GN, 7.7%), renal pelvis and ureter involvement (21.5%), abnormal radiology with quiescent clinical presentation (13.8%), and renal parenchymal lesion plus retroperitoneal fibrosis (RPF, 18.5%) were major lesion types of IgG4-RUD. All patients had elevated serum IgG4, 76.9% had hyperglobulinemia, and 92.3% had elevated serum IgE at diagnosis. IgG4-TIN patients presented with renal dysfunction, and 94.3% had low serum complement C3 and IgG4-GN presented with nephrotic syndrome, while renal pelvis and ureter involvement had normal renal function and urinalysis. IgG4-RPF with renal parenchymal involvement presented with acute renal dysfunction and required emergency medical intervention. Renal cortex low-density areas, parenchyma or pelvis nodular mass, bilateral enlargement of the kidney, and renal pelvis and ureter mass/wall thickening were specific image patterns of IgG4-RUD. Infiltration of plasma lymphocytes and storiform fibrosis were histopathological features of IgG4-RUD. Patients showed satisfactory responses to immunosuppressive treatment, but complete recovery of renal function was difficult to achieve in IgG4-TIN. Four patients (6.2%) experienced clinical relapses during the maintenance period.

Conclusion

IgG4-RUD had diverse lesion types and distinctive manifestations. Radiological examinations were helpful for diagnosis and treatment evaluation. Patients showed good initial response to immunosuppressive treatment but relapses could occur at the maintenance period.

CT Findings of Upper Urinary Tract Lesions in IgG4-Related Disease: Comparison With Urothelial Carcinoma

OBJECTIVE. IgG4-related disease is characterized by extensive infiltration of IgG4-positive plasma cells and fibrosis in various organs. The objective of this study is to investigate CT findings of IgG4-related lesions involving the upper urinary tract and compare them with those of urothelial carcinomas. MATERIALS AND METHODS. This study reviewed pretreatment CT images of 13 consecutive patients with IgG4-related disease with upper urinary tract lesions and 80 consecutive patients with urothelial carcinomas. The findings assessed were laterality, location, growth pattern, margins, internal structure, presence of calcification and lipid component, enhancement pattern, and extraurinary findings. RESULTS. Bilaterality (p < 0.0001), an extramural growth pattern (p < 0.0001), a greater number of affected segments (p = 0.04), and a gradual dynamic enhancement pattern (p < 0.001) were significantly more frequent in patients with IgG4-related disease. With regard to extraurinary findings, paraaortic fat stranding (p = 0.03), presacral fat stranding (p < 0.001), fat stranding of the pelvic walls (p < 0.001), and aortic involvement (p < 0.001) were seen more frequently in patients with IgG4-related disease; on the other hand, there was no statistically significant difference in terms of frequency of pancreatic involvement. Hydronephrosis and renal involvement were seen more frequently in patients with urothelial carcinoma, although the difference was not statistically significant. CONCLUSION. CT findings suggestive of IgG4-related upper urinary tract lesions in comparison with urothelial carcinoma are bilateral and have a longer urinary tract involvement and exhibit an extramural growth pattern, ill-defined margins, a gradual enhancement pattern, aortic involvement, and fat stranding in the paraaortic, presacral, or pelvic wall areas.

A Rare Case of Ureteral IgG4 Disease Masquerading as Urothelial Carcinoma

The present paper described a rare case of ureteral IgG4-related disease (IgG4-RD) that mimicked urothelial carcinoma. An otherwise healthy patient presented with computed tomography, ureteroscopic, and biopsy findings that were suspicious of urothelial carcinoma. The patient received a right nephroureterectomy. Histopathology showed ureteral IgG4-RD, without evidence of urothelial carcinoma. Accurate diagnosis of this rare entity should be based on clinical, biochemical, and histopathological findings.

Histiocytoses: emerging neoplasia behind inflammation

Histiocytoses are disorders characterised by inflammation and the accumulation of cells derived from the monocyte and macrophage lineages, which results in tissue damage. Although they are often considered rare disorders with protean clinical manifestations, considerable advances in the understanding of their genetics have led to increased clinical recognition of these conditions, and fuelled further insights into their pathogenesis. In this Review, we describe insights into the cells of origin, molecular pathology, clinical features, and treatment strategies for some of the most common histiocytic disorders, including Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease. With the discovery of recurrent mutations affecting the mitogen-activated protein kinase and mTOR-AKT pathways in some of these histiocytoses, our understanding of these diseases has now evolved from the concept of a primary inflammatory condition to that of a clonal neoplastic disease. This understanding has led to the development of effective mechanism-based therapeutic strategies for patients with histiocytic diseases.

A Comparative Study of Inflammatory Myofibroblastic Tumors and Tumefactive IgG4-related Inflammatory Lesions: the Relevance of IgG4 Plasma Cells

IgG4-related disease is a recently recognized systemic condition characterized by tumefactive lesions at various sites. Inflammatory pseudotumor (IPT), a tumefactive mass lesion with an unknown etiology, belongs to the spectrum of IgG4-related disease. Inflammatory myofibroblastic tumor (IMT), previously considered under the umbrella of IPT, is now classified as a clonal neoplasm. Previously, both the terms were used interchangeably, because of overlapping morphologic features. This study was carried out to compare the morphologic and the immunohistochemical features of these entities and to study the role of IgG4 in their pathogenesis. Thirty-nine cases comprising of IMT (n=18) and IPT (n=21) were retrieved, and their clinical, morphologic, and immunohistochemical features were studied. IMT was more common in children as compared with IPT. IMT cases showed the proliferation of myofibroblastic cells accompanied by a variable inflammatory infiltrate, whereas IPT cases showed predominantly stromal fibrosis and a lymphoplasmacytic infiltrate with a subset of cases showing a storiform fibrosis and obliterative phlebitis. Anaplastic lymphoma kinase-1 (ALK-1) was positive in 12 of the 18 (66.7%) IMT cases, whereas none of the IPT cases showed ALK-1 immunoreactivity. IPT cases showed significantly increased IgG4+ plasma cells (mean, 127.8/high-power fields vs. 17.8/high-power fields) and a higher IgG4/IgG ratio (mean, 48.2% vs. 10.7%) as compared with IMT. Fluorescence in situ hybridization analysis was positive for ALK rearrangement in 6 of the 9 IMT cases tested. In conclusion, most of the IPT cases can be considered as IgG4 related on the basis of their histopathologic features and immunohistochemistry criteria. However, IMT represents a myofibroblastic neoplasm with ALK-1 overexpression and is clearly not IgG4 related.

IgG4-related inflammatory pseudotumor: A systematic review of histopathological features of reported cases

OBJECTIVES

There is marked inconsistency in reporting the key features of IgG4-related inflammatory pseudotumor (IPT) cases. We aimed to analyze the various aspects of IgG4-related IPTs and to test the performance of the consensus criteria for their diagnosis.

METHODS

PubMed database was searched for IgG4-related IPT cases. The data regarding patient demographics, clinical presentation, laboratory findings, histopathological features, and treatment response are extracted and are presented here in a descriptive manner.

RESULTS

The study included 40 papers describing the clinicopathological features of 83 IPTs in 80 patients. Seventeen cases were diagnosed on biopsies; while remaining were diagnosed on excision specimens. Among these, 50 cases were categorized as highly suggestive and 24 cases as probable for IgG4RD; while nine cases had insufficient histopathological evidence of IgG4RD. Two cases diagnosed on biopsies having insufficient evidence of IgG4RD showed partial or no response to steroids; while 12/14 cases (85.71%) diagnosed on biopsies that were histologically suggestive or probable for IgG4RD showed prompt response to steroids.

CONCLUSION

Many reports have not specifically mentioned the full histopathological findings of IgG4-related IPTs that may hinder in refining the diagnostic criteria of IgG4RD. The IgG4-related IPTs diagnosed on biopsies with requisite features showed prompt response to steroids indicating specificity of histopathological findings in predicting treatment response.

IgG4-related kidney disease--an update

Purpose of review

IgG4-related disease (IgG4-RD) is a recently recognized systemic inflammatory disorder that can affect most organs/tissues such as sarcoidosis. The kidney is a frequently affected organ with tubulointerstitial nephritis (TIN), the representative lesion of IgG4-RD. This review focuses on the latest knowledge of IgG4-related kidney disease (IgG4-RKD).

Recent findings

A wide range of renal manifestations of IgG4-RD, that is TIN, membranous glomerulonephritis (MGN) and other glomerular lesions, and pyelitis, are collectively referred to as IgG4-RKD. Clinically, decreased renal function, or characteristic imaging findings such as multiple low-density lesions on contrast-enhanced computed tomography or diffuse thickening of the renal pelvic wall, are typical presenting features. Although a rapid response to corticosteroid therapy is a very important feature of IgG4-TIN, in cases in which renal function is moderately to severely decreased before therapy, only partial recovery of renal function is obtained.

Summary

TIN with characteristic imaging findings is a typical manifestation of IgG4-RKD in the interstitium, while MGN is a representative manifestation of the glomerular lesions. Although IgG4 is a central feature of IgG4-RD, the recent discovery of IgG4-negative IgG4-RD raises questions about the causative role of the IgG4 molecule in this context.

IgG4-related disease in Italy: clinical features and outcomes of a large cohort of patients

OBJECTIVES

To describe the clinical features, treatment response, and follow-up of a large cohort of Italian patients with immunoglobulin (Ig)G4-related disease (IgG4-RD) referred to a single tertiary care centre.

METHOD

Clinical, laboratory, histological, and imaging features were retrospectively reviewed. IgG4-RD was classified as 'definite' or 'possible' according to international consensus guidelines and comprehensive diagnostic criteria for IgG4-RD. Disease activity was assessed by means of the IgG4-RD Responder Index (IgG4-RD RI).

RESULTS

Forty-one patients (15 females, 26 males) were included in this study: 26 with 'definite' IgG4-RD and 15 with 'possible' IgG4-RD. The median age at diagnosis was 62 years. The median follow-up was 36 months (IQR 24-51). A history of atopy was present in 30% of patients. The pancreas, retroperitoneum, and major salivary glands were the most frequently involved organs. Serum IgG4 levels were elevated in 68% of cases. Thirty-six patients were initially treated with glucocorticoids (GCs) to induce remission. IgG4-RD RI decreased from a median of 7.8 at baseline to 2.9 after 1 month of therapy. Relapse occurred in 19/41 patients (46%) and required additional immunosuppressive drugs to maintain long-term remission. Multiple flares occurred in a minority of patients. A single case of orbital pseudotumour did not respond to medical therapy and underwent surgical debulking.

CONCLUSIONS

IgG4-RD is an elusive inflammatory disease to be considered in the differential diagnosis of isolated or multiple tumefactive lesions. Long-term disease control can be achieved with corticosteroids and immunosuppressive drugs in the majority of cases.

IgG4 related sclerosing mastitis: expanding the morphological spectrum of IgG4 related diseases

IgG4 related disease (IgG4RD) is a recently recognised condition characterised by mass forming lesions associated with storiform fibrosis, obliterative phlebitis, lymphoplasmacytic infiltrate rich in IgG4 positive plasma cells and elevated serum IgG4 levels. Although rare, mammary involvement has been reported as IgG4 related sclerosing mastitis, the morphological counterpart of a growing family of IgG4 related diseases. A total of 17 cases belonging to mass forming benign inflammatory breast lesions such as plasma cell mastitis, granulomatous lobular mastitis, non-specific mastitis and inflammatory pseudotumour were investigated as a possible member of IgG4 related sclerosing mastitis. Clinical, radiological, histopathological and immunohistochemistry findings were noted in all cases. Cases diagnosed as inflammatory pseudotumour showed all the histopathological features of IgG4RD along with increased number of IgG4 positive plasma cells and IgG4/IgG ratio >40%. However, only a few IgG4 positive cells were seen in plasma cell mastitis, granulomatous lobular mastitis and non-specific mastitis cases. These cases also did not fulfill the morphological criteria for the diagnosis of IgG4 related diseases. IgG4RD should be excluded in plasma cell rich lesions diagnosed on core biopsies by IgG4 immunostaining. This can avoid unnecessary surgery as IgG4 related diseases respond to simple and effective steroid treatment.

The changing faces of IgG4-related disease: Clinical manifestations and pathogenesis

Since the earliest reports in 2001, immunoglobulin G4 (IgG4)-related disease has been defined as an autoimmune systemic disease characterized by the lymphoplasmacytic infiltration of affected tissues leading to fibrosis and obliterative phlebitis along with elevated serum IgG4 levels. Prior to this unifying hypothesis, a plethora of clinical manifestations were considered as separate entities despite the similar laboratory profile. The pathology can be observed in virtually all organs and may thus be a challenging diagnosis, especially when the adequate clinical suspicion is not present or when obtaining a tissue biopsy is not feasible. Nonetheless, the most frequently involved organs are the pancreas and exocrine glands but these may be spared. Immunosuppressants lead to a prompt clinical response in virtually all cases and prevent histological sequelae and, as a consequence, an early differential diagnosis from other conditions, particularly infections and cancer, as well as an early treatment should be pursued. We describe herein two cases in which atypical disease manifestations were observed, i.e., one with recurrent neck lymph node enlargement and proptosis, and one with jaundice. Our understanding of the pathogenesis of IgG4-related disease is largely incomplete but data support a significant role for Th2 cytokines with the contribution of innate immunity factors such as Toll-like receptors, macrophages and basophils. Further, macrophages activated by IL4 overexpress B cell activating factors and contribute to chronic inflammation and the development of fibrosis. We cannot rule out the possibility that the largely variable disease phenotypes reflect different pathogenetic mechanisms and the tissue microenvironment may then contribute to the organ involvement.