The Incidence of IgG4-Related and Inflammatory Abdominal Aortic Aneurysm Is Rare in a 101 Patient Cohort

Abdominal aortic aneurysms (AAA) are the most frequent aortic dilation, with considerable morbidity and mortality. Inflammatory (infl) and IgG4-positive AAAs represent specific subtypes of unclear incidence and clinical significance. Here, histologic and serologic analyses with retrospective clinical data acquisition are investigated via detailed histology, including morphologic (HE, EvG: inflammatory subtype, angiogenesis, and fibrosis) and immunhistochemic analyses (IgG and IgG4). In addition, complement factors C3/C4 and immunoglobulins IgG, IgG2, IgG4 and IgE were measured in serum samples and clinical data uses patients' metrics, as well as through semi-automated morphometric analysis (diameter, volume, angulation and vessel tortuosity). A total of 101 eligible patients showed five (5%) IgG4 positive (all scored 1) and seven (7%) inflammatory AAAs. An increased degree of inflammation was seen in IgG4 positive and inflAAA, respectively. However, serologic analysis revealed no increased levels of IgG or IgG4. The operative procedure time was not different for those cases and the short-term clinical outcomes were equal for the entire AAA cohort. Overall, the incidence of inflammatory and IgG4-positive AAA samples seems very low based on histologic and serum analyses. Both entities must be considered distinct disease phenotypes. Short-term operative outcomes were not different for both sub-cohorts.

Vascular/perivascular inflammation in IgG4-related disease

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is characterized by the infiltration of IgG4-positive plasma cells and fibrosclerotic inflammation in multiple organs. Although vascular complications are present in some patients with IgG4-RD, vascular and/or perivascular inflammatory activity compared to control subjects remains unknown. This study sought to investigate vascular/perivascular inflammation in IgG4-RD patients compared to control subjects using 18F-fluorodeoxyglucose-positron emission tomography combined with computed tomography (FDG-PET/CT).

METHODS

We examined 37 consecutive patients diagnosed as IgG4-RD (29 males, mean age of 64.3 ± 8.3 years old), who underwent FDG-PET/CT. Thirty-seven age- and gender-matched subjects without IgG4-RD were employed as controls. Vascular/perivascular inflammation was quantified by blood-normalized standardized uptake value, known as a target-to-background ratio (TBR).

RESULTS

All IgG4-RD patients presented with multiple region involvements. Twelve (32.4%) of the IgG4-RD patients had vascular complications, all of which appeared in the abdominal aorta. IgG4-RD patients had significantly higher TBR values in the descending aorta, abdominal aorta, and common iliac artery than control subjects. Also, IgG4-RD patients with vascular complication exhibited higher TBR values in the infra-renal aorta and common iliac artery than those without vascular complication.

CONCLUSIONS

We found that vascular FDG activity is significantly elevated in IgG4-RD patients regardless of vascular complication than control subjects. FDG-PET/CT is a useful modality for assessing vascular/perivascular inflammation, which may contribute vascular complication in IgG4-RD patients.

Renal Involvement in Retroperitoneal Fibrosis: Prevalence, Impact and Management Challenges

Retroperitoneal fibrosis (RPF) is a rare disorder consisting of idiopathic and various secondary forms and characterized by chronic inflammatory infiltrates and marked fibrosis in the retroperitoneal space. In idiopathic RPF (IRPF), 35–60% of cases have been reported to be IgG4-related RPF, the retroperitoneal lesions of IgG4-related disease (IgG4-RD). IRPF can frequently lead to renal insufficiency mediated by urinary tract obstruction and hydronephrosis irrespective of being IgG4-related or not. Clinical pictures, laboratory and imaging findings, and location of the urinary tract obstruction are generally similar in IgG4-related and non-IgG4-related IRPF although multiple organ involvement and serum IgG4 elevation may be characteristic of the IgG4-related forms. Periaortic/periarterial lesions are the most frequent cause of renal insufficiency. Although the response to glucocorticoids is generally good, relapse does occur in a considerable proportion of patients, and may require an additional immunosuppressive agent and/or urological intervention in cases with multiple relapses or refractory obstructive uropathy. In general, the prognosis of patients with IRPF is good, but careful attention needs to be paid to chronic kidney disease as a major complication and rupture of the affected aorta/artery as a life-threatening one. Further studies are necessary to better understand the pathogenesis of the disease and to establish the optimal diagnostic and therapeutic strategies for it.

Diagnostic Approaches for Large Vessel Vasculitides

The large vessel vasculitides comprise giant cell arteritis (GCA), Takayasu arteritis (TAK), and chronic periaortitis. The diagnostic approach to these conditions involves the correct use and interpretation of clinical criteria, imaging techniques, and, in case of GCA, temporal artery biopsy. Ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT) reveal a homogeneous, concentric, thickening of the arterial wall. MRI and CT may also reveal aneurysms and stenoses. 18F-Fluorodeoxyglucose (FDG)-PET shows increased FDG uptake of inflamed artery walls delineating increased metabolic activity. Ultrasound, FDG-PET, and MRI are the recommended imaging techniques in GCA and TAK. In patients with a high suspicion of GCA who present with visual disturbances, initiation of high-dose intravenous corticosteroids should not be delayed by imaging. Extracranial large vessel vasculitis may be confirmed by all three modalities, particularly by FDG-PET in case of atypical clinical pictures. In this article, we review the role of the GCA and TAK ACR classification criteria, temporal artery biopsy, conventional angiography, ultrasound, MRI, magnetic resonance angiography (MRA), CT angiography (CTA), and FDG-PET in the diagnostic approach of large vessel vasculitis.

Clinical characteristics of IgG4-related retroperitoneal fibrosis versus idiopathic retroperitoneal fibrosis

Retroperitoneal fibrosis (RPF) is an uncommon condition characterized by inflammation and fibrosis in the retroperitoneal space. More than two-thirds of RPF are idiopathic, with the remaining stemed from a variety of secondary causes. It was suggested that IgG4-related RPF is a secondary form of RPF. We undertook this study to compare detailed demographic, clinical and laboratory characteristics of IgG4-related RPF and IRPF in a large Chinese cohort. We retrospectively reviewed the medical records of 132 RPF patients diagnosed at Peking University People’s Hospital between March 2010 and March 2018. Among the 132 patients, the mean age at disease onset was 54.8 years. IgG4-related RPF group showed greater male predominance compared to IRPF group. IgG4-related RPF patients showed a longer interval between symptom onset and diagnosis, and allergic diseases were more common in this group. Sixty-four patients (48.4%) had lower back pain, which was more common in IRPF group than that in IgG4-related RPF patients. In terms of organ involvement, although 42 of 47 patients (89.3%) with IgG4-related RPF had other organ involvement, there were no patients in the IRPF group with other organ involvement. In addition, the serum IgG4 level, elevated eosinophils counts and IgE level were significantly higher in IgG4-related RPF patients. We described the demographic, clinical and laboratory differences between IgG4-related RPF and IRPF patients, indicating their potential differences in pathogenesis, which was of great importance to diagnose and manage the two phenotypes.

Into Clinical Practice: Diagnosis and Therapy of Retroperitoneal Fibrosis

PURPOSE OF THE REVIEW

We aim to review the most relevant diagnostic features and treatment options of retroperitoneal fibrosis, in order to provide a useful guide for clinical practice.

RECENT FINDINGS

The recent literature highlights the role of imaging studies such as computed tomography, magnetic resonance imaging and positron emission tomography as useful tools for the diagnosis of retroperitoneal fibrosis, with retroperitoneal biopsy being reserved to atypical cases. The treatment approach is mainly conservative and is based on the use of medical therapies plus urological interventions. Medical therapies essentially comprise glucocorticoids and immunosuppressants-either traditional or biological agents such as rituximab. Surgical ureterolysis is only left for refractory cases. Recent findings in retroperitoneal fibrosis highlight the possibility of a non-invasive diagnostic approach and a conservative treatment strategy.

The enigmatic immunoglobulin G4-related disease and its varied cardiovascular manifestations

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disease characterised by multiorgan lymphoplasmacytic infiltration, obliterative phlebitis and storiform fibrosis. It can be associated with cardiovascular pathology. The objective of this narrative review is to summarise the published literature on cardiovascular manifestations of IgG4-RD and to provide a basis for diagnosis and management of the condition by the practising cardiologist.We propose the following categorisations of cardiovascular IgG4-RD: aortitis, medium-vessel arteritis, pulmonary vascular disease, phlebitis, valvulopathy, pericarditis, myocardial disease and antineutrophilic cytoplasmic antibody-associated vasculitis. We also review herein developments in radiological diagnosis and reported medical and surgical therapies. Cardiovascular lesions frequently require procedural and/or surgical interventions, such as aortic aneurysm repair and valve replacement. IgG4-RD of the cardiovascular system results in serious complications that can be missed if not evaluated aggressively. These are likely underdiagnosed, as clinical presentations frequently mimic cardiovascular disease due to more common aetiologies (myocardial infarction, abdominal aortic aneurysm and so on). While systemic corticosteroids are the mainstay of IgG4-RD treatment, biological and disease-modifying agents are becoming more widely used. Cardiologists should be aware of cardiovascular IgG4-RD as a differential diagnosis, and understand the roles of corticosteroids, disease-modifying agents and biologicals, as well as their integration with surgical approaches. There are several knowledge gaps, including diagnosis, risk factors, pathogenesis and appropriate management in Ig4-RD of the cardiovascular system. Areas lacking well-conducted randomized trials include safety of steroids in the setting of vascular aneurysms and the role of disease-modifying drugs and biological agents in patients with established cardiovascular complications of this multifaceted enigmatic disease.

Overview of IgG4-related aortitis and periaortitis. A decade since their first description

Aortic involvement is relatively common in the context of IgG4-related disease (IgG4-RD). It includes IgG4-aortitis, and IgG4-(chronic) periaortitis (IgG4-CP). The latter overlaps with IgG4-retroperitoneal fibrosis (IgG4-RPF). Aortic wall thickening which characterizes these entities along with the presence of periaortic tissue in IgG4-CP, are often accompanied by aortic aneurysms, which belong to the group of the so-called inflammatory aneurysms. Both the thoracic and abdominal aorta can be affected. Aortitis appears to involve more often the former, while the opposite is the case for IgG4-CP. There is a lack of definitions and different classification criteria have been used to describe these entities. This report provides an overview on the current evidence of aortic involvement in IgG4-RD. It discusses the clinical, epidemiologic, serologic and histopathologic characteristics, as well as the imaging techniques used for their diagnosis and the therapeutic options and treatment outcomes. The differential diagnosis and underlying pathogenetic mechanisms are also discussed.

Standardized approach to idiopathic retroperitoneal fibrosis: a comprehensive review of the literature

BACKGROUND

Idiopathic retroperitoneal fibrosis (iRPF) is a rare fibro-inflammatory disease, characterized by inflammation of the abdominal aorta and its surrounding structures. The exact pathophysiology remains unclear. Diagnosis is often troublesome due to the non-specific and highly variable clinical presentation. Standardized treatment protocols are lacking.

OBJECTIVE

This article presents a review on iRPF, addressing clinical and diagnostic modalities as well as its pathophysiology and the possible inclusion within the IgG4-related disease (IgG4-RD) spectrum. Finally, a diagnostic-therapeutic algorithm for a standardized approach to iRPF is proposed.

METHODS

The PubMed Internet database was searched. Articles were selected based on the relevance of abstract, article type and impact of the journal.

RESULTS

iRPF and IgG4-RD share a common autoimmune aetiology. Diagnostics are multimodal and based on imaging. Ruling out malignancy should be of primary concern. Complications are mostly of renal or vascular origin due to compression of retroperitoneal structures. Corticosteroids remain the first-line treatment regimen and are mostly successful, but evidence supporting alternative immunosuppressive and anti-inflammatory treatments is growing. Long-term therapy, as well as follow-up, is paramount in this chronic and often relapsing disease.

IgG4-related aortitis/periaortitis and periarteritis: a distinct spectrum of IgG4-related disease

BACKGROUND

Large vessels could be involved in immunoglobulin (Ig)-G4-related disease (IgG4-RD). This study aimed to clarify the clinical features and evaluate the treatment efficacy for IgG4-RD with aortitis/periaortitis and periarteritis (PAO/PA).

METHODS

This study prospectively enrolled 587 patients with IgG4-RD with a follow-up time of more than 6 months. The distribution of IgG4-related PAO/PA was classified into four types: type 1, thoracic aorta; type 2a, abdominal aorta; type 2b, abdominal aorta and iliac artery; type 2c, iliac artery; type 3, thoracic and abdominal aorta; and type 4, other arteries. Patient's demographic data, clinical characteristics, laboratory parameters, and treatment efficacy were analyzed.

RESULTS

Of 587 IgG4-RD patients, 89 (15.2%) had PAO/PA. The average age was 58.3 ± 11.1 years, with male predominance (85.4%). Vessels affected were as follows: abdominal aorta (83.1%), iliac artery (70.8%), thoracic aorta (13.5%), and other vessels (13.5%). The most prevalent distribution type of IgG4-related PAO/PA was type 2b, with 74 (83.1%) patients, followed by type 2a, type 2c, type 3, and type 1. Fifty-five (61.8%) PAO/PA patients had hydronephrosis, with renal insufficiency occurring in 43 (48.3%), and 31 (34.8%) PAO/PA patients had D-J stent drainage due to severe ureteral obstruction. After treatment with a glucocorticoid and immunosuppressants, 82% patients achieved remission with shrinking of the perivascular mass by more than 30%.

CONCLUSIONS

IgG4-RD with PAO/PA was distinct from non-PAO/PA in demographic features, organ involvement distribution, inflammatory markers, and serum IgG4 and IgE. The most common affected vessel was the abdominal aorta, and most patients responded well with treatment.

Characteristics and prognosis of IgG4-related periaortitis/periarteritis: A systematic literature review

OBJECTIVE

Immunoglobulin G4 (IgG4)-related disease is a systemic chronic fibroinflammatory disease that can affect almost every organ of the body. IgG4-related periaortitis/periarteritis is a newly recognized subset of IgG4-related disease, and its characteristics and prognosis remain unclear. We investigated the clinical characteristics and prognosis of IgG4-related periaortitis/periarteritis.

METHODS

We performed a systematic literature review of IgG4-related periaortitis/periarteritis. Additionally, we have summarized the characteristics and prognosis of IgG4-related coronary arteritis.

RESULTS

We investigated 248 patients with IgG4-related periaortitis/periarteritis. All studies reported the condition in elderly patients, and male predominance was observed. The infra-renal abdominal aorta and iliac arteries were the most commonly affected sites. Most reports showed the serum C-reactive protein elevation in this disease entity, in contrast to non-vascular IgG4-related disease. Based on radiological findings observed in 27 patients with IgG4-related coronary arteritis, vasculitic lesions were classified into 3 types: stenotic (67% of patients), aneurysmal (42%), and diffuse wall thickening type (92%). Serum IgG4 level, but not C-reactive protein level, was associated with the number of affected organs in IgG4-related coronary arteritis. Corticosteroid treatment with or without cardiac surgery or percutaneous coronary intervention was effective in most patients with IgG4-related coronary arteritis; however, 33% of patients showed an unfavorable clinical course including disease progression, relapse, or death. Pre-treatment stenosis and/or aneurysms were associated with progression of stenosis or aneurysm after corticosteroid treatment.

CONCLUSION

Most clinical characteristics were similar between the IgG4-related periaortitis/periarteritis and the non-vascular IgG4-related disease groups; however, serum C-reactive protein level elevation was observed only in the former. Although corticosteroid treatment was effective, this disease can be life-threatening secondary to myocardial infarction, aortic dissection, and aneurysmal rupture. Pre-treatment evaluation of stenosis or aneurysms is important for predicting progression of stenosis or aneurysm after corticosteroid treatment.

Idiopathic Retroperitoneal Fibrosis: Long-term Risk and Predictors of Relapse

RATIONALE & OBJECTIVE

Idiopathic retroperitoneal fibrosis (IRF) is a rare disorder of unknown cause. Medical therapy can induce remission, but disease relapses are common. This study sought to characterize long-term outcomes of IRF and the factors associated with disease recurrences.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Retrospective analysis of 50 patients with IRF prospectively followed up for 8.9 (IQR, 4.7-12.7) years at a tertiary-care referral center.

EXPOSURES

Demographic, clinical, treatment, and laboratory parameters, including measures of autoimmunity.

OUTCOME

Disease relapse.

ANALYTICAL APPROACH

Proportional hazards analysis for the subdistribution of competing risks.

RESULTS

49 patients received medical treatment and 35 underwent interventional procedures. All patients experienced a clinical response (defined as regression of disease-related symptoms and hydronephrosis, and decrease in the maximal transverse diameter of the retroperitoneal mass on computed tomography of >50%), 44 of whom responded within 1 year. The remaining 6 responded over a median of 2.95 years after starting therapy. 40 patients were alive at last observation, 1 receiving maintenance dialysis and 15 with estimated glomerular filtration rate < 60mL/min/1.73m². Patient survival at 5, 10, and 15 years was 95%, 84%, and 68%, respectively. 19 (38%) patients had at least 1 relapse (occurring a median of 5.19 years after starting therapy), defined as an increase in serum creatinine level of at least 30% or recurrence/development of hydronephrosis and ≥20% increase in the maximal transverse diameter of the retroperitoneal mass on computed tomography. Cumulative incidences of relapse at 5, 10, and 15 years were 21%, 41%, and 48%, respectively. Baseline antinuclear antibody positivity and male sex were associated with relapse (subdistribution hazard ratios [sHRs] of 5.35 [95% CI, 2.15-13.27] and 4.94 [95% CI, 1.32-18.57], respectively), while higher corticosteroid therapy dosage at 1 year (sHR for relapse per 1-mg/d greater dosage, 0.91 [95% CI, 0.84-0.98]) and treatment with prednisone alone or with tamoxifen (sHR for relapse of 0.25 [95% CI, 0.07-0.85] vs other therapies) were associated with lower rate of relapse.

LIMITATIONS

Small sample size and variable approaches to therapy.

CONCLUSIONS

IRF relapses were common and were experienced more frequently by male patients. Corticosteroids alone or with tamoxifen were associated with a lower rate of relapse. The strong association of antinuclear antibody positivity with relapse supports the hypothesis of an autoimmune pathogenesis of IRF.

Clinical and Prognostic Significance of Serum IgG4 in Chronic Periaortitis. An Analysis of 113 Patients

Objective: Chronic periaortitis (CP) is a rare fibro-inflammatory disorder that incorporates idiopathic retroperitoneal fibrosis, inflammatory abdominal aortic aneurysms, and perianeurysmal retroperitoneal fibrosis. CP is included in the spectrum of IgG4-related disease. Since CP patients rarely undergo diagnostic biopsies, serum IgG4 levels are often used to classify CP as IgG4-related. However, the clinical and prognostic significance of serum IgG4 in CP is unknown.

Methods: We measured serum IgG4 in active CP patients and compared the clinical characteristics, response to therapy and outcome of patients with high and normal levels. We also tested the diagnostic significance of IgG4 by comparing its levels in CP patients, healthy and disease controls (malignancies, Erdheim-Chester disease, large-, and small-vessel vasculitis).

Results: We studied 113 consecutive patients with active CP. Twenty-four (21.2%) had high serum IgG4 (>135 mg/dL). The demographic, laboratory, and clinical characteristics of patients with high and normal IgG4 were similar, and so were the rates of ureteral obstruction and the disease characteristics on CT, MRI, and ¹⁸F-FDG-PET. Patients with high IgG4 only had a higher frequency of extra-retroperitoneal fibro-inflammatory lesions (p = 0.005). There were no significant differences in response to therapy and relapses between the two groups. Serum IgG4 levels did not discriminate CP from controls.

Conclusions: Serum IgG4 levels are high in a minority of CP patients and do not identify specific clinical or prognostic subgroups; only a higher frequency of extra-retroperitoneal lesions is found in high-IgG4 patients. Serum IgG4 levels do not help in the differential diagnosis between CP and its mimics.

Retroperitoneal fibrosis in the era of immunoglobulin G4-related disease

Background

Retroperitoneal fibrosis (RPF) is a rare disease characterized by fibroinflammatory tissue in the periaortic or periiliac retroperitoneum, where it frequently encases ureters. There is emerging evidence that a subset of this disease is part of a spectrum of multisystemic autoimmune diseases collectively referred to as “immunoglobulin G4 (IgG4)-related disease”.

Methods

We retrospectively analyzed 27 idiopathic RPF patients and identified a subset as IgG4-related RPF, which we categorized according to recently published comprehensive diagnostic criteria. We compared clinical and laboratory characteristics and response to treatment between the two groups.

Results

Of 27 total patients, 16 (59.3%) were diagnosed as having IgG4-related RPF, and these were predominantly male. They were also significantly older and more likely to have other organ involvement, hydronephrosis, and postrenal acute kidney injury (AKI) compared to those with idiopathic RPF. However, there was no difference in response rate to systemic steroid treatment.

Conclusion

IgG4-related RPF accounts for a substantial portion of RPF cases previously identified as “idiopathic RPF” in Korea. Clinical and laboratory characteristics of IgG4-related RPF are similar to those of idiopathic RPF except for a striking male predominance, older age, and higher incidence of postrenal AKI in IgG4-related RPF. More comprehensive, prospective studies are needed to clearly distinguish IgG4-related RPF from idiopathic RPF based on clinical manifestation and to further assess treatment response and long-term prognosis.

Enormous Aneurysm in Coronary Artery Fistula With Immunoglobulin G4-Related Disease

We report the first case of coronary artery fistula with aneurysmal change in a patient with immunoglobulin G4-related disease (IgG4-RD). This case revealed concomitant coronary artery dilation, pericardial inflammatory nodules, and coronary-pulmonary fistula aneurysm in addition to several IgG4-RD lesions. Each of these features was located in close proximity to the thickened pericardium. These lesions might result from inflammation of the pericardial space, which extended to the coronary-pulmonary artery vessels, leading to aneurysmal formation. This case will enhance our understanding of the pathological mechanisms of IgG4-RD inflammation.

Clinical features of IgG4-related periaortitis/periarteritis based on the analysis of 179 patients with IgG4-related disease: a case-control study

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a newly recognized systemic condition characterized by high serum immunoglobulin G4 (IgG4) concentration and IgG4-bearing plasma cell infiltration in affected organs. Although it has become evident that IgG4-RD also involves the systemic aortic/arterial system, the precise details of this condition remain unclear. The present study sought to clarify the clinical features of IgG4-related periaortitis/periarteritis.

METHODS

Among 223 patients with IgG4-RD, 179 (131 male, median onset age 67 years) were recruited for this study. Periaortitis/periarteritis was defined as vessel wall thickness with circumferential enhancement on contrast-enhanced computed tomography.

RESULTS

Periaortitis/periarteritis was identified in 65 (36.3%; 53 male) of 179 IgG-RD patients. The distribution of IgG4-related periaortitis/periarteritis could be broadly classified into five types, with the most prevalent Type 2 (44.6%) being localized at the infra-renal artery portion of the abdominal aorta and continuing to the iliac arteries. The infra-renal artery region of the abdominal aorta was most frequently involved (>80%) among IgG4-related periaortitis/periarteritis cases. Comparisons of clinical parameters between IgG4-RD patients with and without periaortitis/periarteritis revealed significantly higher propensities for older IgG4-RD onset age and highly active disease state featuring elevated serum IgG, IgG4, circulating immune complex, and soluble interleukin-2 receptor. All patients showed improvement of wall thickening after steroid therapy, although nine patients (20.9%) exhibited worsening of luminal dilatation. The main risk factor for this manifestation was prior luminal dilatation according to multivariate analysis.

CONCLUSION

IgG4-related periaortitis/periarteritis predominantly occurred at the infra-renal artery portion of the abdominal aorta, affected older IgG4-RD onset patients, and was prevalent in highly active disease states. As reported previously, the main risk factor for worsening luminal dilation after corticosteroid therapy was the existence of luminal dilation beforehand.

Immunoglobulin G4-related Coronary Periarteritis and Luminal Stenosis in a Patient with a History of Autoimmune Pancreatitis

Immunoglobulin G4 (IgG4)-related disease is a systemic inflammatory disorder that was first described in patients with autoimmune pancreatitis. Although IgG4-related disease is thought to involve the cardiovascular system, case reports describing coronary artery involvement are relatively rare. We describe a patient who was previously diagnosed with autoimmune pancreatitis and found to have coronary periarteritis and luminal narrowing. After the initiation of steroid treatment, the patient's coronary periarteritis and luminal stenosis were both ameliorated with an improvement in the serum IgG4 concentration. The present findings collectively suggest that IgG4-related immuno-inflammation may have a role in the development of coronary periarteritis and luminal atherosclerosis.

The value of 18F-FDG PET/CT in the distinction between retroperitoneal fibrosis and its malignant mimics

OBJECTIVE

To discuss the utility of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computerized tomography (PET/CT) in the diagnosis of idiopathic retroperitoneal fibrosis (iRPF).

METHODS

IRPF patients diagnosed between September 2011 and June 2016 were included. Retroperitoneal malignancy patients were included as control. The morphological features and FDG uptake of retroperitoneal lesions were measured along with lymph node (LN) mapping.

RESULTS

Seventy-one iRPF patients were included. Fifteen lymphoma patients and 6 retroperitoneal metastatic malignancy patients were included as control. Significant differences in morphological features were observed between iRPF and lymphoma but not retroperitoneal metastatic carcinoma. Compared with malignancy, iRPF displayed a lower frequency of high-FDG-uptake retroperitoneal lesions (P = 0.017) and a lower mean maximum standardized uptake value (SUV_max) (P < 0.001). LNs located at axillary, retroperitoneal, supraclavicular, inguinal or peritoneal sites were more frequently observed in retroperitoneal malignancy, therefore, were defined as specific LNs. The area under the curve (AUC) for SUV_max was 0.893 with a sensitivity of 85.7% and a specificity of 80.3%, when the cut-off value of the SUV_max was 6.23. The AUC for the logistic regression model combining the lesions above renal arteries, the SUV_max and the number of specific LNs was 0.987 with a sensitivity of 90.5% and a specificity of 98.6%. The risk stratification model analysis indicated that most of the retroperitoneal malignancy patients were at moderate or high level, while most of the iRPF patients were at low risk.

CONCLUSIONS

Retroperitoneal malignancy can mimic iRPF morphologically. ¹⁸F-FDG PET/CT can help to distinguish iRPF from retroperitoneal lymphoma and metastatic malignancy.

Idiopathic retroperitoneal fibrosis and its overlap with IgG4-related disease

Retroperitoneal fibrosis (RPF) is a rare disease characterised by fibrous tissue proliferation in the retroperitoneum, with encasement of the ureters and large vessels of the abdomen as the most destructive of potentially severe complications. It can either be idiopathic, or secondary to infections, malignancies, or the use of certain drugs. The idiopathic form accounts for approximately 75% of the cases, and is usually responsive to immunosuppressive therapy. In recent years, the emergence of a new clinical entity, IgG4-related disease (IgG4-RD), shed light on many fibro-inflammatory disorders once thought to be separate clinical entities, although frequently associated in the so-called multifocal fibrosclerosis. Among these, together with sclerosing pancreatitis and cholangitis, pseudotumour of the orbit, idiopathic mediastinal fibrosis and other conditions, is idiopathic retroperitoneal fibrosis (IRF). Both IRF and IgG4-RD can be associated with a wide variety of disorders, usually governed by immune-mediated (and particularly auto-immune) mechanisms. In our review, we discuss the clinical and therapeutic challenges IRF presents to the internist, as well as the meaning of its recent inclusion in the IgG4-RD spectrum from a clinical practice standpoint.

Elevated serum IgG4 levels in diagnosis and treatment response in patients with idiopathic retroperitoneal fibrosis

Idiopathic retroperitoneal fibrosis (iRPF) may be a manifestation of IgG4-related disease. Measuring serum IgG4 (sIgG4) may be of value in monitoring iRPF, but this has scarcely been evaluated. It is unknown if tamoxifen (TMX) affects sIgG4 levels. We performed a prospective inception cohort study of 59 patients with untreated (re)active iRPF stratified by elevated (>1.4 g/L) or normal sIgG4 level. Changes in sIgG4 levels following TMX initiation and, if treatment failed, during subsequent corticosteroid (CS) treatment were analyzed. The median sIgG4 level was 1.1 g/L (interquartile range (IQR) 0.4-2.2); 24 patients (40%) had elevated sIgG4 level. Patients with elevated sIgG4 tended to present with higher ESR (46 vs. 34 mm/h; P = 0.08) and more frequent locoregional lymphadenopathy adjacent to the mass (41.7 vs. 20.0%; P = 0.08). sIgG4 also correlated with ESR (ρ = 0.26; P = 0.05) and serum creatinine (SC) (ρ = 0.26; P = 0.04). Following TMX initiation, sIgG4 level decreased, particularly when achieving treatment success (P < 0.01). Odds ratio for TMX treatment success in patients with elevated sIgG4 level was 0.77 (95% CI 0.53-1.14; P = 0.19). After adjusting for age, sex, and SC, the odds ratio was 0.78 (95% CI 0.51-1.18; P = 0.24). ROC curve analyses of sIgG4 on a continuous scale and treatment success showed an AUC of 0.62. Treatment success and concurrent sIgG4 decrease (P < 0.01) were achieved in 78% of patients who converted to CS therapy. Patients with elevated sIgG4 level may be more inflammatory than patients with normal sIgG4 level, but this needs further study. TMX affects sIgG4 levels, but to a lesser extent than CSs. sIgG4 cannot be used as an outcome prediction tool, irrespective of which cutoff value was chosen.

Retroperitoneal fibrosis - the state-of-the-art

Retroperitoneal fibrosis (RPF) is a rare disease, hallmarked by inflammation and deposition of fibrous tissue around the abdominal aorta. This process may spread contiguously and involve adjacent structures, leading to many complications, among which the most frequent and most severe is ureteral obstruction. The condition usually has idiopathic origin (idiopathic retroperitoneal fibrosis – IRF), but can also develop secondarily to a number of factors. The etiology of the disease remains unclear. Current research suggests that about half of the cases of IRF may be a symptom of a recently discovered, clinically heterogeneous immunoglobulin G4-related disease (IgG4-RD). Corticosteroids are the first-line treatment for IRF, but effective attempts to use immunosuppressants are also made. This paper presents the current state of knowledge on the etiopathogenesis, clinical presentation, diagnosis and therapeutic possibilities in different forms of RPF. Based on the latest research, an analysis of the relationship between IRF and IgG4-RD was performed.

Non-IgG4-related Multifocal Fibrosclerosis

Multifocal fibrosclerosis (MFS), which causes systemic and chronic connective tissue inflammation, has been associated with IgG4 and regarded as an identical entity with "IgG4-related disease (IgG4-RD)". Although a few cases of MFS mimicking IgG4-RD histopathologically, despite the absence of a serum IgG4 elevation and IgG4-positive plasma cell infiltration, have been reported, there is, so far, little information regarding such exceptional cases. We herein demonstrate a case of non-IgG4-related MFS presenting with periaortitis and parotiditis, whose histological findings were consistent with IgG4-RD despite the absence of elevated serum and tissue IgG4 levels.

An elevated IgG4 response in chronic infectious aortitis is associated with aortic atherosclerosis

Recently, it was shown that infectious bacterial aortitis can stimulate an elevated IgG4⁺ plasma cell response in the vessel wall, which could mimic IgG4 aortitis/periaortitis. However, the factors that are associated with an elevated IgG4⁺ plasma cell response in infectious aortitis are unclear. To ascertain these factors, 17 cases of infectious aortitis and 6 cases of non-infectious severe abdominal aortic atherosclerosis were assessed for the magnitude of IgG4⁺ plasma cell response. The degree of IgG4⁺ plasma cell infiltration was determined by immunohistochemistry. Infectious cases were subcharacterized as chronic (>3 weeks duration) or acute (<3 weeks duration) based on the duration of symptoms, and as involving either the ascending aorta or the distal aorta, ie, the descending thoracic and/or abdominal aorta. There was a 5-16-fold greater degree of IgG4⁺ plasma cell infiltration in the chronic distal infectious aortitis group compared with the other three infectious aortitis groups (P ≤ 0.0007), and compared with non-infectious severe abdominal aortic atherosclerosis (P<0.0008). This resulted in a greater IgG4/IgG ratio in the chronic distal infectious aortitis group compared with the acute ascending and acute distal infectious aortitis groups (P<0.03). The degree of IgG4⁺ plasma cell infiltration in chronic distal infectious aortitis overlaps with that seen in the aortitis and periaortitis of IgG4-related disease. In the chronic infectious aortitis cases, the degree of IgG4⁺ plasma cell infiltration was more intense in patients with moderate to severe aortic atherosclerosis compared with those patients with less aortic atherosclerosis (P=0.007). These findings indicate that an elevated IgG4⁺ plasma cell response occurs in the descending thoracic and abdominal aorta in the setting of chronic bacterial infectious aortitis and pre-existing atherosclerosis. This inflammatory response to chronic infection in atherosclerosis-laden aortas may have implications for the development of IgG4-rich inflammatory atherosclerotic aortic aneurysms.