Characterizing IgG4-related disease with ¹⁸F-FDG PET/CT: a prospective cohort study

Imaging findings in cardiovascular involvements of IgG4-related disease: a systematic review study

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition characterized by IgG4-positive plasma cell infiltration that can affect multiple organs, including the cardiovascular system. The diagnosis of IgG4-RD relies on a combination of clinical, serological, radiological and pathological findings. However, due to the varied and insidious clinical presentations, normal IgG4 levels in a significant percentage of patients and frequent multi-organ involvement, imaging plays a crucial role in the diagnosis of IgG4-RD. The aim of this study is to comprehensively examine the imaging findings in IgG4-related cardiovascular disease for accurate diagnosis and appropriate treatment.

METHODS

A systematic search was conducted across the electronic databases PubMed, Scopus, Embase and Web of Science, to 1 September 2023, following PRISMA guidelines, searching for studies reporting detailed cardiovascular imaging findings in IgG4-RD.

RESULTS

The search yielded 68 studies (60 case reports, 5 case series, 2 cross-sectional, 1 case-control) with 120 cases of cardiovascular IgG4-RD. Most of the cases were male, averaging 62.8 years. The common initial symptoms were dyspnoea and chest pain. The most common imaging finding was vasculopathy, including vessel wall thickening, periarteritits, periaortitis, aortitis, stenosis, ectasia, aneurysm formation, intramural haemorrhage, fistula formation and dissection, followed by pericardial involvement and mediastinal masses. Case series and cross-sectional studies also showed vasculopathy to be the most common finding on various imaging modalities, including angiography and PET/CT, highlighting the complex pathology of IgG4-RD.

CONCLUSION

This study evaluated current IgG4-RD articles, revealing a higher prevalence in men and vasculopathy as the most common cardiovascular complication.

A 69-year-old man with generalised lymphadenopathy, glandular swelling and pleural effusion

Patients with multisystemic presentation including respiratory symptoms and generalised lymphadenopathy should alert the clinician to this potential diagnosis https://bit.ly/4eJ0PHT.

IgG4-Related Lymphadenopathy Mimicking Mediastinal Lymph Node Metastasis of Lung Cancer on 18F-FDG PET/CT

We report a case of a 73-year-old man with minimally invasive lung adenocarcinoma, post-resection, evaluated with 18F-FDG PET/CT for suspected disease progression. Imaging showed increased FDG uptake in the right lower lung mass and systemic lymphadenopathy (mediastinal, supraclavicular, axillary, paraaortic, and iliac regions). The appearance of a stable lymph node and a clinical history of IgG4 lymphadenopathy suggested an inflammatory process, although malignancy in the lung mass and mediastinal nodes could not be excluded. Lobectomy confirmed the presence of lung adenocarcinoma, while radical lymph node dissection identified IgG4-related lymphadenopathy without metastasis. This case underscores the need for considering differential diagnosis of PET-positive lymphadenopathy, especially in patients with comorbid conditions that mimic or coexist with malignancy.

Comparative Analysis of Classification Criteria in IgG4-Related Disease and Evaluating Diagnostic Accuracy from a Retrospective Cohort in Clinical Practice

INTRODUCTION

We conducted a comprehensive comparative analysis of the Okazaki, Umehara, and American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria for diagnosing immunoglobulin G4-related disease (IgG4-RD).

MATERIALS AND METHODS

A retrospective study was conducted in a single tertiary hospital, using expert clinical judgment as the gold standard. We compared the diagnostic accuracy of the Okazaki, Umehara, and ACR/EULAR criteria in a cohort of 41 patients with suspected IgG4-RD. We assessed sensitivity, specificity, and positive and negative predictive values for each criterion, and conducted a separate analysis based on four IgG4-RD subtypes.

RESULTS

A total of 30 patients were confirmed to have IgG4-RD and 11 were identified as mimickers. The Umehara criteria demonstrated the highest sensitivity (83.33%), followed by the ACR/EULAR 2019 (66.67%) and Okazaki (60.0%) criteria. All three criteria exhibited 100% specificity, with overall diagnostic accuracy ranging from 70% to 88%. The areas under the curve (AUC) were 0.917 (Umehara), 0.800 (Okazaki), and 0.833 (ACR/EULAR 2019), indicating significant diagnostic effectiveness (p < 0.000). Subtype analysis revealed that the Umehara and ACR/EULAR 2019 criteria were more effective in diagnosing pancreato-hepato-biliary involvement (subtype 1), while the Okazaki and ACR/EULAR 2019 criteria were more effective in diagnosing retroperitoneal fibrosis and/or aortitis (subtype 2).

CONCLUSIONS

Our study provides valuable insights into the diagnostic performance of the Okazaki, Umehara, and ACR/EULAR criteria for a cohort of patients with suspected IgG4-RD. The Umehara criterion demonstrated the highest sensitivity, suggesting its potential utility for screening purposes, while all three criteria showed consistent specificity.

Imaging of the Major Salivary Glands in Rheumatic Disease

Salivary gland involvement is a common feature of rheumatologic disease. The authors review the anatomy of the major salivary glands and the uses of imaging modalities such as ultrasound, MRI, computed tomography, sialography, and scintigraphy in evaluating the major salivary glands in rheumatologic disease.

[Application of 18F-FDG PET/CT in rheumatic diseases]

OBJECTIVE

To explore the application of 18F-flurodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in rheumatic diseases, to compare these different imaging features, and to describe the current PET/CT imaging status in clinical practice.

METHODS

A total of 486 cases in our department from January 2012 to December 2018 were enrolled in this study, and 18F-FDG PET/CT examination was performed in all the patients. The clinical use of 18F-FDG PET/CT was retrospectively analyzed to discuss the clinical application and its imaging characteristics of rheumatic diseases. Categorical data were used to ascertain prevalence statistics, whereas continuous data were used to delineate means and standard deviations. Independent sample t test, Chi square test and Mann-Whitney U test were used for statistical analysis. A P-value of < 0.05 was considered significant.

RESULTS

(1) From 2012 to 2018, totally 486 patients in the Department of Rheumatology and Immunology underwent 18F-FDG PET/CT examination, accounting for 5.30% of the total number of PET/CT examinations in the whole hospital. In this study, 304 of the 486 patient were female (62.55%), 182 of them were male (37.45%), the average age of the patients was (53.21±18.81) years, and the proportion of the patients aged 45-65 (227/486, 46.71%) was the highest group. (2) Three leading purposes of the PET/CT examination in our department were to exclude cancers (55.56%), assist in diagnosis (24.60%) and evaluate the disease activity (19.84%). (3) Of the 486 patients who underwent 18F-FDG PET/CT, 327 cases might indicate a differential diagnosis of rheumatic disease, of which, 292 cases were highly suggestive of diagnosis, including 61 cases of myositis, 60 cases of vasculitis, 37 cases of adult still's disease, 32 cases of IgG4 related diseases, 30 cases of rheumatoid arthritis, 22 cases of Sjögren's syndrome, 22 cases of systemic lupus erythematosus, and 9 cases of rheumatic polymyalgia; the remaining 35 cases only prompted the possibility of autoimmune disease. Of the 486 patients, 74 cases suggested the diagnosis of cancers, 25 cases indicated the diagnosis of infectious diseases, while 60 cases could not show any diagnostic values. Ten patients with rheumatic disease were followed up with a post-treatment repeat PET/CT, and the findings in remission showed reduced 18F-FDG metabolic activity as well as a reduction in the extent of metabolic hypertrophic lesions.

CONCLUSION

There are some typical sign of 18F-FDG PET/CT for diffuse connective tissue diseases, therefore 18F-FDG PET/CT has auxi-liary effect on the classification diagnosis of rheumatic diseases, especially for the exclusion of cancers.

Emerging multimodality imaging techniques for the pulmonary circulation

Pulmonary hypertension (PH) remains a challenging condition to diagnose, classify and treat. Current approaches to the assessment of PH include echocardiography, ventilation/perfusion scintigraphy, cross-sectional imaging using computed tomography and magnetic resonance imaging, and right heart catheterisation. However, these approaches only provide an indirect readout of the primary pathology of the disease: abnormal vascular remodelling in the pulmonary circulation. With the advent of newer imaging techniques, there is a shift toward increased utilisation of noninvasive high-resolution modalities that offer a more comprehensive cardiopulmonary assessment and improved visualisation of the different components of the pulmonary circulation. In this review, we explore advances in imaging of the pulmonary vasculature and their potential clinical translation. These include advances in diagnosis and assessing treatment response, as well as strategies that allow reduced radiation exposure and implementation of artificial intelligence technology. These emerging modalities hold the promise of developing a deeper understanding of pulmonary vascular disease and the impact of comorbidities. They also have the potential to improve patient outcomes by reducing time to diagnosis, refining classification, monitoring treatment response and improving our understanding of disease mechanisms.

Volume-Based Quantitative Measurement of [18F]AlF-NOTA-FAPI-04 PET/CT Uptake Reflects the Disease Activity of IgG4-Related Disease

BACKGROUND

To investigate the potential utility of quantitative parameters obtained by 18F-fibroblast activation protein inhibitor positron emission tomography/computed tomography ([18F]AlF-NOTA-FAPI-04 PET/CT) in the assessment of organ involvement and disease activity in IgG4-related disease (IgG4-RD).

METHODS

This study enrolled patients who underwent [18F]AlF-NOTA-FAPI-04 PET/CT scans at the Department of Rheumatology, The First Affiliated Hospital, Zhejiang University School of Medicine from August 2021 to August 2022. The PET/CT images of the included patients were re-evaluated by PET center technicians, and the maximal standardized uptake value (SUVmax), metabolic lesion volume (MLV), and total lesion FAPI (TL-FAPI) were used to evaluate the involved organs and tissues that abnormally accumulated [18F]AlF-NOTA-FAPI-04. The clinical and laboratory data of patients are also systematically collected and analyzed.

RESULTS

Among the patients included in this study, 12 patients met the IgG4-RD classification criteria established by the American College of Rheumatology in 2019. Among them, 8 were males and 4 were females, with an average age of 59.3 ± 11.5 years. 50% of IgG4-RD patients were found with more organ involvement on PET/CT than physical examination, ultrasonography, and computed tomography. IgG4 levels (Rho = 0.594, p = 0.042) and IgG4-RI (Rho = 0.647, p = 0.023) were significantly positively correlated with TL-FAPI. After linear regression analysis, only TL-FAPI showed a predictive value of RI (R2 = 0.356, B = 0.008, p = 0.041).

CONCLUSIONS

[18F]AlF-NOTA-FAPI-04 PET/CT is a useful tool for identifying asymptomatic organ involvement and assessing disease activity. The TL-FAPI as an indicator was positively correlated with IgG4-RD disease activity.

Advances in understanding and management of IgG4-related ophthalmic disease

Immunoglobulin G4-related ophthalmic disease (IgG4-ROD) is an emerging, immune-mediated fibroinflammatory orbital disease, characterized by tumefactive lesions with noticeable IgG4+ plasma cell infiltration and distinctive pathohistological features. This disease is often associated with elevated serum IgG4 concentrations. IgG4-ROD may affect any ophthalmic tissues, particularly the lacrimal gland, extraocular muscles, and trigeminal nerves. Although the exact pathogenic role of IgG4 antibodies remains unclear, B-cell depleting agents have been reported to be an effective treatment. The diverse clinical manifestations of IgG4-ROD complicate diagnosis, and without prompt treatment, visual-threatening complications such as optic neuropathy may arise. Recent advances in understanding and managing IgG4-ROD have revolutionized the diagnosis and treatment of this emerging disease. This review article aims to provide a comprehensive overview of the latest advancements in the field of IgG4-ROD.

18 F-FDG PET/CT in Pediatric Immunoglobulin G4-Related Disease

ABSTRACT

A 14-year-old boy presented with severe, nonintentional weight loss, fatigue, and cough. Investigations were notable for raised inflammatory markers and significantly elevated serum immunoglobulin G4 (IgG4). 18 F-FDG PET/CT was obtained for assessment of disease involvement and extent, to exclude differential diagnoses and to guide biopsy. The study demonstrated extensive FDG-avid nodal disease and multisystem organ involvement. Excisional biopsy of a right inguinal lymph node demonstrated reactive changes with numerous IgG4-positive plasma cells consistent with IgG4-related disease. He was commenced on immunosuppressive therapy with consequent weight restoration and symptom resolution.

PET/CT in Inflammatory and Auto-immune Disorders: Focus on Several Key Molecular Concepts, FDG, and Radiolabeled Probe Perspectives

Chronic immune diseases mainly include autoimmune and inflammatory diseases. Managing chronic inflammatory and autoimmune diseases has become a significant public health concern, and therapeutic advancements over the past 50 years have been substantial. As therapeutic tools continue to multiply, the challenge now lies in providing each patient with personalized care tailored to the specifics of their condition, ushering in the era of personalized medicine. Precise and holistic imaging is essential in this context to comprehensively map the inflammatory processes in each patient, identify prognostic factors, and monitor treatment responses and complications. Imaging of patients with inflammatory and autoimmune diseases must provide a comprehensive view of the body, enabling the whole-body mapping of systemic involvement. It should identify key cellular players in the pathology, involving both innate immunity (dendritic cells, macrophages), adaptive immunity (lymphocytes), and microenvironmental cells (stromal cells, tissue cells). As a highly sensitive imaging tool with vectorized molecular probe capabilities, PET/CT can be of high relevance in the management of numerous inflammatory and autoimmune diseases. Relying on key molecular concepts of immunity, the clinical usefulness of FDG-PET/CT in several relevant inflammatory and immune-inflammatory conditions, validated or emerging, will be discussed in this review, together with radiolabeled probe perspectives.

Current and future advances in practice: IgG4-related disease

IgG4-related disease (IgG4-RD) is an increasingly recognized cause of fibroinflammatory lesions in patients of diverse racial and ethnic backgrounds and is associated with an increased risk of death. The aetiology of IgG4-RD is incompletely understood, but evidence to date suggests that B and T cells are important players in pathogenesis, both of which are key targets of ongoing drug development programmes. The diagnosis of IgG4-RD requires clinicopathological correlation because there is no highly specific or sensitive test. Glucocorticoids are highly effective, but their use is limited by toxicity, highlighting the need for studies investigating the efficacy of glucocorticoid-sparing agents. B cell-targeted therapies, particularly rituximab, have demonstrated benefit, but no randomized clinical trials have evaluated their efficacy. If untreated or under-treated, IgG4-RD can cause irreversible organ damage, hence close monitoring and consideration for long-term immunosuppression is warranted in certain cases.

Appropriate timing to perform an interim 18F-FDG PET/CT in patients with nasal-type extranodal natural killer/T cell lymphoma

Interim 18F-FDG PET/CT (I-PET) has a role in response evaluation and treatment guidance in patients with nasal-type extranodal natural killer/T cell lymphoma (ENKTL). However, there was no agreement on the timing of I-PET performed, after chemotherapy or after chemoradiotherapy. We aimed to find the appropriate timing for I-PET by assessing the prognostic value of I-PET in response evaluation in ENKTL patients. Two hundred and twenty-seven ENKTL patients who had undergone I-PET were retrospectively included. All patients were grouped based on their therapeutic strategy received, chemotherapy or chemoradiotherapy. The Deauville 5-point score (DS) was used to interpret the I-PET images. The hazard ratio (HR) and C-index were used to measure the discriminatory and prognostic capacities of I-PET performed at different times. One hundred and six patients underwent the I-PET after chemotherapy (chemotherapy group), while I-PET was performed after chemoradiotherapy in 121 patients (chemoradiotherapy group). Eighty-seven patients were classified as metabolic remission (DS score of 1-3), while the other 140 were classified as non-metabolic remission (DS score of 4-5) according to the Deauville criteria. There were no significant survival differences between patients in metabolic remission and in non-metabolic remission in either progression-free survival (PFS, p = 0.406) or overall survival (OS, p = 0.350). In the chemotherapy group, patients in metabolic remission had significantly superior PFS than patients in non-metabolic remission (p = 0.012). For OS, a discriminative trend was also found on the survival curve between patients in metabolic remission and in non-metabolic remission (p = 0.082). In the chemoradiotherapy group, there was no significant difference in PFS (P = 0.185) or OS (P = 0.627) between patients in metabolic remission and in non-metabolic remission. I-PET after chemotherapy yields higher discriminative power and has the ability for prognostic prediction in nasal-type ENKTL patients. I-PET after radiochemotherapy has no prognostic value. Thus, the appropriate timing for I-PET is after chemotherapy but before radiotherapy for response evaluation in nasal-type ENKTL patients.

Mimickers of immunoglobulin G4-related hepatobiliary disease on biopsy

With the growing recognition of IgG4-related hepatobiliary disease, establishing a definitive diagnosis relies mainly on a combination of clinical findings, serological markers, and imaging modalities. However, the role of histopathological evaluation remains indispensable, particularly in cases necessitating differential diagnosis or malignancy exclusion. While diagnosing IgG4-related hepatobiliary disease through surgical resection specimens is often straightforward, pathologists encounter substantial challenges when evaluating biopsies. The increasing rarity of surgical interventions exacerbates this due to improved disease recognition and suspicion. Numerous confounding factors, including the absence of the characteristic histologic features, limited tissue sample size, biopsy artifacts, and the limited value of IgG4 counts, further complicate the diagnostic process. Additionally, many other disorders exhibit clinical and histological features that overlap with IgG4-related disease, intensifying the complexity of interpreting biopsy specimens. This article explores the clinical and histomorphologic features of IgG4-related hepatobiliary disease and its potential mimickers. It offers valuable insights for pathologists and clinicians when confronted with biopsy specimens from hepatobiliary organs.

Utility of 18F-FDG PET/CT for differential diagnosis between IgG4-related lymphadenopathy and angioimmunoblastic T-cell lymphoma

AIM

To explore the utility of the 2-[18F]-fluoro-2-deoxy-d-glucose (18F-FDG) positron-emission tomography (PET)/computed tomography (CT) in the differential diagnosis of IgG4-related lymphadenopathy (IgG4-RLAD) and angioimmunoblastic T-cell lymphoma (AITL).

MATERIALS AND METHODS

Retrospective analysis of 18F-FDG PET/CT imaging findings in clinically diagnosed IgG4-RLAD and AITL cases was undertaken to record the distribution, morphological characteristics, and imaging features of the affected lymph nodes, as well as FDG uptake of the spleen and bone marrow. Standardised uptake values normalised to lean body mass were evaluated for maximum (SULmax), average (SULavg), and peak values (SULpeak). Univariate and multivariate logistic regression was used to screen for statistically significant imaging findings to discriminate IgG4-RLAD from AITL.

RESULTS

Twenty-two cases of IgG4-RLAD (17 men, five women, median age 49.5 years) and 22 cases of AITL (16 men, six women, median age 55 years) were finally included in the analysis. There were no AITL patients with involvement of a single lymph node region. AITL patients had more involvement of the different nodal regions except cervical and pelvic nodal regions. A practical assessment method based on a combination of SULpeak-LN/SULavg-liver, SULpeak-spleen, and the number of involved nodal regions, improved the performance for differential diagnosis between both groups with an overall classification accuracy of 90.9%.

CONCLUSIONS

18F-FDG PET/CT is a useful tool for distinguishing AITL from IgG4-RLAD, and it can also help determine the optimal biopsy site for suspected cases of IgG4-RLAD or AITL, reduce the need for re-biopsy procedures, and enable physicians to develop timely treatment strategies.

18F-FDG PET/CT imaging of IgG4-producing MALT lymphoma with multiple site involvement

18F-FDG PET/CT is regarded as a modality utilized for the purpose of lesion localization, staging and assessment of treatment response in patients with lymphoma. However, it is difficult that we diagnose among multifocal lymphoma, IgG4-related disease (IgG4-RD), or a combination of both conditions when confronted with multiple sites of 18F-FDG uptake with heightened serum IgG4 levels. We present a case of a 72-year-old male who was suspected of Sjögren's syndrome based on symptoms of xerostomia accompanied by swelling of the bilateral upper eyelid and salivary glands. Following a diagnostic biopsy that revealed mucosa-associated lymphoid tissue (MALT) lymphoma as a possible finding, 18F-FDG PET/CT was conducted, which demonstrated multiple sites of 18F-FDG accumulation. While multifocal MALT lymphoma was initially suspected, the coexistence of IgG4-RD could not be definitively ruled out due to the elevated serum IgG4 levels. Subsequent histopathological and immunohistochemical examinations confirmed the diagnosis of IgG4-producing MALT lymphoma. After receiving systemic therapy with rituximab, the swelling of the bilateral upper eyelid and parotid glands resolved upon visual examination, and the serum IgG4 levels returned to within the normal range in a few months. No new lesions were detected during the subsequent follow-up examinations conducted over a period of 3 years.

IgG4-related cholangitis - a mimicker of fibrosing and malignant cholangiopathies

IgG4-related cholangitis (IRC) is the major hepatobiliary manifestation of IgG4-related disease (IgG4-RD), a systemic fibroinflammatory disorder. The pathogenesis of IgG4-RD and IRC is currently viewed as multifactorial, as there is evidence of a genetic predisposition while environmental factors, such as blue-collar work, are major risk factors. Various autoantigens have been described in IgG4-RD, including annexin A11 and laminin 511-E8, proteins which may exert a partially protective function in cholangiocytes by enhancing secretion and barrier function, respectively. For the other recently described autoantigens, galectin-3 and prohibitin 1, a distinct role in cholangiocytes appears less apparent. In relation to these autoantigens, oligoclonal expansions of IgG4+ plasmablasts are present in patients with IRC and disappear upon successful treatment. More recently, specific T-cell subtypes including regulatory T cells, follicular T helper 2 cells, peripheral T helper cells and cytotoxic CD8+ and CD4+ SLAMF7+ T cells have been implicated in the pathogenesis of IgG4-RD. The clinical presentation of IRC often mimics other biliary diseases such as primary sclerosing cholangitis or cholangiocarcinoma, which may lead to inappropriate medical and potentially invalidating surgical interventions. As specific biomarkers are lacking, diagnosis is made according to the HISORt criteria comprising histopathology, imaging, serology, other organ manifestations and response to therapy. Treatment of IRC aims to prevent or alleviate organ damage and to improve symptoms and consists of (i) remission induction, (ii) remission maintenance and (iii) long-term management. Glucocorticosteroids are highly effective for remission induction, after which immunomodulators can be introduced for maintenance of remission as glucocorticosteroid-sparing alternatives. Increased insight into the pathogenesis of IRC will lead to improved diagnosis and novel therapeutic strategies in the future.

Rheumatology experience with FDG PET / CT in inflammation of unknown origin: a single - centre report for determining factors associated with diagnostic precision

BACKGROUND / AIM: The use of PET / CT is becoming more common in the elucidation of inflammatory processes in which the underlying cause cannot be determined by conventional examinations. Although PET / CT is an effective method for detecting inflammatory foci, the precise diagnosis may not be obtained in all cases. In addition, considering factors such as radiation exposure and cost, it becomes important to identify patients who can get results with PET / CT. In this study, it was aimed to examine the factors that can predict the differential diagnostic value of PET / CT by retrospectively scanning patients who underwent PET / CT for inflammation of unknown origin (IUO) in rheumatology practice.

METHODS

Demographic, clinical and laboratory information of the patients followed up in our clinic and who underwent PET / CT for differential diagnosis were enrolled. Whether they were diagnosed after PET / CT and during the follow - up period, and their diagnoses were examined.

RESULTS

A total of 132 patients were included in the study. A previous diagnosis of rheumatic disease was present in 28.8 % of the patients, and a history of malignancy was present in 2.3 % . The patients were divided into three groups: group 1 patients with increased FDG uptake in PET / CT and diagnosis confirmed by PET / CT, group 2 patients with increased FDG uptake in PET / CT but diagnosis was not confirmed, and group 3 patients without increased FDG uptake in PET / CT. Increased FDG uptake in PET / CT was detected in 73 % of the patients. While PET / CT helped the diagnosis in 47 (35.6 %) patients (group 1), it did not help the diagnosis in 85 (64.4 %) (groups 2 and 3). Thirty - one (65.9 %) of the diagnosed patients were diagnosed with a rheumatologic disease. When the 3 groups were compared, male gender, advanced age, CRP levels, presence of constitutional symptoms, SUVmax values and number of different organs with increased FDG uptake were higher in Group 1. Sixty - six percent and 74 % of the patients in groups 2 and 3 were not diagnosed during the follow - up period. No patient in group 3 was diagnosed with malignancy during follow - up.

CONCLUSION

PET / CT has high diagnostic value when combined with clinical and laboratory data in the diagnosis of IUO. Our study revealed that various factors can affect the diagnostic value of PET / CT. Similar to the literature, the statistically significant difference in CRP levels shows that patients with high CRP levels are more likely to be diagnosed with an aetiology in PET / CT. Although detection of involvement in PET / CT is not always diagnostic, there was an important finding that no malignancy was detected in the follow - up in any patient without PET / CT involvement. Key points • PET / CT is an effective method for detecting inflammatory foci. • PET / CT has proven to be effective in the diagnosis of rheumatological diseases, the extent of disease and the evaluation of response to treatment. • Indications for the use of PET / CT in the field of rheumatology and the associated factors and clinical features supporting the diagnosis with PET / CT are still to be fully clarified. • In routine practice, with PET / CT, both delays in diagnosis and examinations performed during diagnosis and the cost can be reduced.

Pretherapy 18F-FDG PET/CT in Predicting Disease Relapse in Patients With Immunoglobulin G4-Related Disease: A Prospective Study

OBJECTIVE

To investigate whether the levels of inflammation detected by ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) can predict disease relapse in immunoglobulin G4-related disease (IgG4-RD) patients receiving standard induction steroid therapy.

MATERIALS AND METHODS

This prospective study analyzed pretherapy FDG PET/CT images from 48 patients (mean age, 63 ± 12.9 years; 45 males and 3 females) diagnosed with IgG4-RD between September 2008 and February 2018, who subsequently received standard induction steroid therapy as the first-line treatment. Multivariable Cox proportional hazards models were used to identify the potential prognostic factors associated with relapse-free survival (RFS).

RESULTS

The median follow-up time for the entire cohort was 1913 days (interquartile range [IQR], 803-2929 days). Relapse occurred in 81.3% (39/48) patients during the follow-up period. The median time to relapse was 210 days (IQR, 140-308 days) after completion of standardized induction steroid therapy. Among the 17 parameters analyzed, Cox proportional hazard analysis identified whole-body total lesion glycolysis (WTLG) > 600 on FDG-PET as an independent risk factor for disease relapse (median RFS, 175 vs. 308 days; adjusted hazard ratio, 2.196 [95% confidence interval: 1.080-4.374]; P = 0.030).

CONCLUSION

WTLG on pretherapy FDG PET/CT was the only significant factor associated with RFS in IgG-RD patients receiving standard steroid induction therapy.

Renal Involvement of Immunoglobulin G4-Related Disease Presenting as a Solitary Hypermetabolic Mass Mimicking Renal Tumor on 18F-FDG PET/CT

ABSTRACT

A 62-year-old woman with a 5-year history of diabetes insipidus was found with a solitary renal mass in contrast-enhanced CT. 18F-FDG PET/CT showed a hypermetabolic mass in the right kidney. Besides, there was increased uptake in the pituitary stalk. The histopathological examination of renal biopsy confirmed the diagnosis of immunoglobulin G4-related disease. After treatment with prednisone and cyclophosphamide, there was obvious radiographic improvement of the renal lesion.

Patterns of Relapse and Complications of Immunoglobulin G4-Related Disease

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a multisystemic fibroinflammatory condition potentially resulting in organ dysfunction. We aimed to evaluate imaging characteristics of disease relapse and complications in this cohort of patients.

METHODS

This was a cohort study of IgG4-RD patients imaged between 2010 and 2020. Radiological manifestations of disease activity (remission/stability vs. relapse and complications) were correlated with clinical symptoms. Univariate analyses were performed with χ2, Fisher exact, and Mann-Whitney U tests. Times to relapse and organ atrophy were studied with Kaplan-Meier analyses.

RESULTS

A total of 69 patients had imaging surveillance over a median duration of 47 months. Radiological relapse occurred in 50.7% (35/69) with median time to relapse at 74 months (95% confidence interval, 45-122 months); 42.8% (15/35) of this cohort had different-site relapse with the following recognized primary-secondary patterns: pancreas-hepatobiliary (p = 0.005), hepatobiliary-pancreas (p = 0.013), and periaortitis-mesenteric (p = 0.006). Clinical symptoms were significantly associated with imaging characteristics (p < 0.001). Abdominal complications were detected in 52.2% (36/69) of patients, mostly solid organ atrophy (97.2% [35/36]). New-onset diabetes was more likely in pancreatic IgG4-RD (n = 51) when accompanied by gland atrophy (4/21 vs. 0/30 nonatrophy, p = 0.024).

CONCLUSION

Radiological relapse of IgG4-RD is common over prolonged imaging surveillance and is significantly associated with symptomatic relapse. A multisystem review to detect new/different sites of disease and abdominal complications may help predict future organ dysfunction.

Semi-quantitative indices of 2-[18F]FDG PET/CT in assessing cardiovascular and non-cardiovascular manifestations of IgG4-related disease and treatment response

BACKGROUND

IgG4-related disease (IgG4-RD) is a heterogeneous autoimmune disorder characterised by inflammatory lesions. Diagnostic imaging, such as 2-[¹⁸F]FDG PET/CT, is critical in evaluation of the disease, especially for potentially lethal cardiovascular manifestations. This retrospective study examines the usefulness of semi-quantitative parameters of 2-[¹⁸F]FDG PET/CT in monitoring IgG4-RD in patients with and without cardiovascular manifestations.

METHODS

Patients diagnosed with IgG4-RD who underwent a 2-[¹⁸F]FDG PET/CT scan were identified and classified based on presence or absence of cardiovascular disease. Clinical and laboratory data were extracted and compared to three 2-[¹⁸F]FDG PET/CT semi-quantitative parameters: maximum standardised uptake value (SUVmax), metabolic tumour volume (MTV), and total lesion glycolysis (TLG). Tissue-to-background blood (TBR) values were also evaluated for cardiovascular manifestations. These data were also compared in patients before and after receiving immunosuppressive therapy.

RESULTS

Forty-six patients identified were divided into an eight member subgroup of patients with cardiovascular manifestations, and a thirty-eight member subgroup of patients without. Patients with cardiovascular lesions were most frequently identified incidentally on imaging evaluation for other diseases (37.5%), with none presenting with chest pain or other cardiovascular symptoms. Ten patients with pre-treatment and post-treatment 2-[¹⁸F]FDG PET/CT scans demonstrated significant decreases in all semi-quantitative parameters, with no significant decrease in total IgG or ESR. The decrease in SUVmax, MTV, TLG following therapy was replicated in patients with and without cardiovascular manifestations.

CONCLUSION

2-[¹⁸F]FDG PET/CT is an important investigation to determine all sites of involvement in this multisystemic disease and to rule out life-threatening cardiovascular manifestations even in the absence of symptoms. Semi-quantitative parameters such as SUVmax, MTV, TLG, and TBR are useful in assessing treatment response in patients. There are no serological substitutes that can quantify the extent of disease involvement like 2-[¹⁸F]FDG PET/CT.

Development of an algorithm for IgG4-related disease management

OBJECTIVES

IgG4-related disease (IgG4-RD) is a rare fibro-inflammatory condition affecting multiple organs lacking standardized management. In this article, we review the evidence available to provide European expert-based statements on the management of IgG4-RD which were integrated in a final algorithm.

METHODS

A panel of nine European experts in IgG4-RD from different specialties was asked to elaborate a set of consensus statements through a Delphi exercise. Three rounds of survey were taken. Consensus was reached when ≥75% of the responders agreed with a statement.

RESULTS

Thirty-one statements on induction treatment, maintenance treatment, non-pharmacological treatment, and general considerations were assessed. Patients should be treated promptly in situations when there is an immediate organ threatened, or when organ damage is anticipated. Glucocorticoids (GC) are considered the first line of treatment and should be progressively tapered. Maintenance treatment is recommended for patients with high disease activity or with risk factors for relapse. Rituximab is effective for induction and maintenance of remission, but its use can be limited by economics. Low dose GC with or without GC-sparing agents can be used for maintenance therapy. Stenting or surgery should be ancillary to pharmacological treatment. Follow up should be based on physical examination, blood works, and imaging studies. Furthermore, it should be tailored on individual patient clinical history. 18-fluorodeoxyglucose positron emission tomography/computerized tomography may provide additional information over other imaging modalities.

CONCLUSIONS

These new statements and algorithm reached a high degree of agreement and may help guiding the clinical management of IgG4-RD.

Positron Emission Tomography Imaging in Vasculitis

Systemic vasculitides comprise a group of autoimmune diseases affecting blood vessels. [18F]-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (FDG-PET/CT) plays an important role in the diagnosis and therapeutic monitoring of vasculitides affecting large-sized and medium-sized vessels. FDG-PET/CT also provides complementary information to other vascular imaging tools. The resolution and sensitivity of newer generation scanners continues to increase, hereby improving the ability of FDG-PET/CT to accurately assess the full disease extent in patients with vasculitis. Novel tracers targeting specific immune cells will allow for more detailed detection of vascular infiltrates.

Thoracic manifestations of IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year. The disease can affect virtually any organ and is characterized by unifying histopathological findings. Recently, four subgroups of patients have been characterized: hepatobiliary, head and neck, Mikulicz syndrome and retroperitoneal fibrosis, who illustrate the mainly abdominal and ENT tropism of the disease. Yet, thoracic involvement is not uncommon. It can be detected in up to 30% of patients with systemic IgG4-RD and is the exclusive manifestation of the disease in about 10% of cases. Clinical symptoms are nonspecific and may include dyspnoea, cough or chest pain. Chest CT findings are heterogeneous and primarily include peribronchovascular thickening, nodules, ground-glass opacities and lymphadenopathy. There is no specific diagnostic test for IgG4-RD thoracic involvement, which may mimic malignancy or vasculitis. Therefore, a cautious approach is needed to make an accurate diagnosis: a search for extra-thoracic manifestations, elevated serum IgG4 levels, circulating levels of plasmablasts and pathologic evidence of disease is warranted. Although very suggestive, neither the presence of a polyclonal IgG4 lymphoplasmacytic infiltrate, storiform fibrosis or obliterative phlebitis are sufficient to confirm the histological diagnosis. Steroids are recommended as first-line therapy. Rituximab or disease-modifying antirheumatic drugs may be used in relapsed or rare cases of steroid-refractory disease. In this review, we summarize current knowledge regarding the pathophysiology, epidemiology, diagnostic modalities (clinical-biological-imaging-histopathology) and treatment of IgG4-RD thoracic involvement.

Multidisciplinary diagnosis and management of inflammatory aortic aneurysms

BACKGROUND

Inflammatory abdominal aortic aneurysms (IAAAs) are a variant involving a distinct immunoinflammatory process, with nearly one half believed to be associated with IgG4-related disease (IgG4-RD).

METHODS

MEDLINE and Google Scholar searches were conducted for English-language publications relevant to inflammatory aortic aneurysms from January 1970 onward. The search terms included inflammatory aortic aneurysms, aortitis, periaortitis, IgG4-related disease, and retroperitoneal fibrosis. Relevant studies were selected for review based on their relevance.

RESULTS

Morphologically, IAAAs are characterized by a thickened aneurysm wall often displaying contrast enhancement and elevated metabolic activity on fluorine-18 fluorodeoxyglucose-positron emission tomography imaging. A strong association exists with perianeurysmal and retroperitoneal fibrosis. Although the rupture risk appears lower with IAAAs than with noninflammatory abdominal aortic aneurysms (AAAs), the currently recommended diameter threshold for operative management is the same. Open repair has been associated with increased morbidity compared with noninflammatory AAAs, and a retroperitoneal approach or minimal dissection transperitoneal approach has been recommended to avoid duodenal and retroperitoneal structural injuries. Endovascular aneurysm repair has been increasingly used, especially for patients unfit for open surgery. It is important to exclude an infectious etiology before the initiation of immunosuppressive therapy or operative repair. Multimodality imaging follow-up is critical to monitor disease activity and secondary involvement of retroperitoneal structures by the associated fibrotic process. Maintenance of immunosuppressive therapy will be needed postoperatively for most patients with active systemic disease, especially those with IgG4-RD and those with persistent symptoms. Additional interventions aimed at ureteral decompression could also be required, and lifelong follow-up is mandatory.

CONCLUSIONS

Preoperative multimodality imaging is a diagnostic cornerstone for assessment of the disease extent and activity. IgG4-RD is an increasingly recognized category of IAAAs, with implications for tailoring adjunctive medical therapy. Open surgical repair remains the procedure of choice, although endovascular aneurysm repair is increasingly being offered. Maintenance immunosuppressive therapy can be offered according to the disease activity as assessed by follow-up imaging studies.

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.

AuntMinnie Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Leads to Diagnosis of Immunoglobulin G4-Related Disease

A 61-year-old male underwent fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) for evaluation of fever and weight loss with clinical suspicion of occult malignancy or tuberculosis. The scan showed hypermetabolism in bilateral submandibular salivary glands, biliary radicles, pancreas, bilateral kidneys, prostate, and multiple lymph nodes. Based on the concomitant involvement of these sites, suspicion of immunoglobulin G4 (IgG4)-related disease was raised in PET-CT report. Further evaluation with serum IgG4 levels and histopathology of the submandibular salivary gland confirmed the diagnosis of IgG4-related disease. The ability of FDG PET-CT to evaluate the whole-body status of disease played a crucial role in this case.

Different Uptake of 68Ga-FAPI and 18F-FDG in Lymphadenopathy Caused by Angioimmunoblastic T-Cell Lymphoma in a Patient with Colon Cancer

An 82-year-old man with a history of colon cancer was found with multiple lymphadenopathies and a pulmonary mass. Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) detected generalized hypermetabolic lymph nodes and an FDG-avid pulmonary mass. PET/CT with ⁶⁸Ga-labeled fibroblast activation protein inhibitor (FAPI) revealed intense uptake in the lung mass, consistent with metastatic disease from colon cancer. However, the lymphadenopathies were not avid for ⁶⁸Ga-FAPI, suggesting a different etiology. The biopsy of a cervical node confirmed angioimmunoblastic T-cell lymphoma. The case showcased the potential of ⁶⁸Ga-FAPI in differentiation of solid tumor and hematological disease due to different histopathologic nature of stromal fibrosis.

From Suspicion to Diagnosis: Analysis on the Clinical Characteristics of 37 Cases of IgG4-Related Disease (IgG4-RD) in Northeast China

INTRODUCTION

IgG4-related disease (IgG4-RD) mimics a variety of disorders, the final diagnosis is heavily dependent on the doctor's familiarity with the disease, most patients are expected to get a good prognosis by early diagnosis and timely treatment.

METHODS

Retrospective analysis was carried out on 147 patients tested for serum IgG4 because of suspected IgG4-RD. These cases were grouped as the IgG4-RD group and non-IgG4-RD group according to the diagnostic criteria proposed by the Japanese IgG4-RD research group and the American College of Rheumatology and the European Union of Rheumatology. Characteristics of these patients were investigated and analyzed.

RESULTS

The onset age of IgG4-RD was 57.29 ± 14.03 years old, male to female ratio of IgG4-RD was 1.31:1. The most commonly affected organs were the pancreas (48.6%), lymph nodes (40.5%) and biliary tract (35.1%), the proportion of patients with simultaneous involvement of multiple organs is as high as 83.2%. A history of allergy is more common in IgG4-RD patients (32.4% vs 14.5%), the optimal critical value of serum IgG4/IgG ratio for diagnosis of IgG4-RD was 0.09 (sensitivity 94.7%, specificity 91.7%) and the optimal threshold for IgG diagnosis of IgG4-RD was 15.25g/L (sensitivity 73.7%, specificity 77.8%) in this study.

CONCLUSION

IgG4-RD is often manifested as multiple organ involvement, and is most likely to involve the pancreas, biliary tract and lymph nodes. Most patients were diagnosed in other departments instead of rheumatology. Serum IgG4 level, especially IgG4/IgG ratio has a higher predictive value for IgG4-RD. Early diagnosis is the key point to improve the prognosis.

18F-fluorodeoxyglucose PET and PET/computed tomography for the evaluation of immunoglobulin G4-related disease: a systematic review

BACKGROUND

In the last years, 18F-fluorodeoxyglucose PET/computed tomography (18F-FDG PET/CT) has demonstrated its utility for the evaluation of immunoglobulin G4 (IgG4)-related disease (IgG4RD). The studies are, however, really heterogeneous and different. The aim of this review is, therefore, to analyze the diagnostic performance of 18F-FDG PET and PET/CT for the assessment of IgG4RD.

METHODS

A wide literature search of the PubMed/MEDLINE, Scopus, Embase and Cochrane library databases was made to find relevant published articles about the diagnostic performance of 18F-FDG PET or PET/CT for the evaluation of IgG4RD.

RESULTS

The comprehensive computer literature search revealed 779 articles. On reviewing the titles and abstracts, 756 articles were excluded because the reported data were not within the field of interest. Twenty-three studies were included in the review.

CONCLUSION

Despite some limitations that affect our review, 18F-FDG PET or PET/CT demonstrated the ability to assess IgG4RD both at initial evaluation and after therapy. In general, no correlation between PET/CT parameters and IgG4 serum levels has been reported. A possible role for 18F-FDG PET/CT to drive differential diagnosis with other disease is starting to emerge.

The role of imaging in immunoglobulin G4-related disease of the upper urinary tract

Background

Immunoglobulin G4-related disease remains a modern, relatively unknown field in the urological world. An increasing number of cases require urological input, often with invasive diagnostics and aggressive medical treatment first-line. Given this, we sought to evaluate modern radiological options of disease affecting the upper urinary tract, to provide clarity and reduce diagnostic burden and delay in this poorly understood yet potentially debilitating disease process.

Summary

We conducted a systematic literature search including PubMed and Medline, focusing on immunoglobulin G4-related disease affecting the upper urinary tract, before reviewing articles assessing different radiological modalities in diagnosis. Consistent computed tomography findings have been demonstrated in the literature and contributed to recent breakthroughs in classification criteria, however invasive biopsy remains a mainstay in work-up, given the difficulties in comparing against malignancy. Early work in positron-emission tomography and magnetic resonance imaging has shown promise in radiologically distinguishing from other differentials, especially diffusion-weighted imaging showing high sensitivity levels, but not yet enough to formulate protocols and cause histological investigation to be redundant.

Key messages

Our article has highlighted repeated findings in the literature of computed tomography appearances of IgG4-RD in the upper urinary tract, however invasive work-up remains a mainstay given the overlap with malignancy. Prospective, comparative studies into magnetic resonance imaging and positron-emission tomography are now required, given their early results, to improve consistency in reporting and reduce patient burden when investigating this benign, yet debilitating disease process.

Clinical value of 18F-FDG PET/CT in IgG4-related disease

OBJECTIVE

To investigate the clinical value of ¹⁸F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in IgG4-related disease (IgG4-RD).

METHODS

Seventy two patients diagnosed with IgG4-RD who underwent PET/CT were included. Correlations between clinical variables and PET/CT findings were analyzed by Spearman's correlation test. Conventional radiology was compared to PET/CT to evaluate detection discrepancies. The detection ability of insidious organ involvement by PET/CT at disease onset was investigated. The utility value of PET/CT for the 2019 ACR/EULAR classification criteria was analyzed with the multivariate logistic analysis and ROC curve.

RESULTS

SUV_max of main involved organ was positively correlated with IgG4-RD Responder Index (IgG4-RD RI), serum and tissue IgG4 levels and IgG4/IgG ratio, serum eosinophils counts and number of involved organs, while negatively correlated with serum IgM levels. PET/CT was superior in detecting organ/tissue involvements including prostate, gastrointestinal tract and lung compared with conventional imaging. For patients with pancreato-hepato-biliary or head-neck involvements at onset, PET/CT showed superiority in detecting insidious lesions. Multivariate analysis showed that disease duration, multiple-organ involvement, SUV_max of main involved organ and mean SUV_max of all involved organs were significantly associated with the fulfillment of the 2019 ACR/EULAR classification criteria. ROC curves indicated that the cut-off value for SUV_max of main involved organ and mean SUV_max of all involved organs for fulfillment of the 2019 ACR/EULAR classification criteria for IgG4-RD were 4.1 and 3.5, respectively.

CONCLUSION

¹⁸F-FDG PET/CT has potential capacity to monitor disease activity, evaluate organ involvements and assist in the classification criteria in IgG4-RD.

2-deoxy-2[18F]fluoro-D-glucose positron emission tomography-computed tomography in rheumatological diseases

2-deoxy-2[18F]fluoro-D-glucose (FDG) PET-CT has revolutionized oncological imaging. The cellular processes that make cancer cells visible on FDG PET-CT also occur in a number of inflammatory cells. Exploiting this phenomenon has led to a growth of evidence supporting the use of FDG PET-CT in a wide range of infective and inflammatory diseases. Rheumatological diseases can affect multiple sites within the musculoskeletal system alongside multi-organ extra-articular disease manifestations. Inflammation is central to these diseases, making FDG PET-CT a logical choice. In this review article we describe the various applications of FDG PET-CT in rheumatological diseases using illustrative examples to highlight the beneficial role of FDG PET-CT in each case.

IgG4-Related Disease: Mimickers and Diagnostic Pitfalls

BACKGROUND

The tendency of IgG4-related disease (IgG4-RD) to form pseudotumors, as well as its multisystemic nature, makes it the perfect mimicker of many conditions. Moreover, some clinical, serological, radiological, or histological features of the disease might be shared with some mimickers.Recently, 4 clinical phenotypes have been identified, and patients grouped in each phenotype have distinctive demographic, clinical, and serological features and outcomes, and, as expected, for each phenotype, a set of differential diagnoses should be considered.

SUMMARY OF THE LITERATURE

The main differential diagnoses for the pancreato-hepato-biliary phenotype are pancreatic adenocarcinoma and cholangiocarcinoma. Other differential diagnoses include type 2 autoimmune pancreatitis and primary sclerosing cholangitis. In patients with retroperitoneal/aortic phenotype, inflammatory conditions such as idiopathic retroperitoneal fibrosis and large vessel vasculitides should be ruled out, and most of the time, a biopsy will be needed to exclude malignancies. In head and neck limited phenotype, autoimmune conditions (eg, granulomatosis with polyangiitis, Graves orbitopathy, sarcoidosis), malignancies, and histiocytosis should be ruled out, whereas the main differential diagnoses of the Mikulicz/systemic phenotype are Sjögren syndrome, granulomatosis with polyangiitis, and multicentric Castleman disease.

CONCLUSIONS

Approaching a patient with probable IgG4-RD through a clinical phenotype framework will ease the diagnostic algorithm and facilitate the prompt recognition of the disease. There are certain clinical, serological, radiological, and histological features in each clinical phenotype that, if present, increase the likelihood that a patient may have IgG4-RD instead of the mimicker condition. Those clues that point toward IgG4-RD diagnosis should be actively sought in the workup of patients.

Active IgG4-related disease with bone marrow involvement: a report of 2 cases and case-based review

IgG4-related disease (IgG4-RD) is a systemic fibro-inflammatory disease, histopathologically characterized by dense lymphoplasmacytic infiltration rich in IgG4-positive plasma cells in affected organs. Classic hematologic presentations including lymphadenopathy, eosinophilia and polyclonal hypergammaglobulinemia are common, whereas bone marrow involvement of IgG4-RD is rarely reported. Here we present two patients of multi-organ IgG4-RD with bone marrow involvement, one on bone marrow biopsy, and the other on PET/CT. Presentations of other organ involvement included biopsy-proven IgG4-related tubulointerstitial nephritis, lymphadenopathies, submaxillary glands, arteritis, asthma, dysosmia, and constitutional symptoms. Bone marrow involvement was initially suspected due to leukopenia, anemia and thrombocytopenia in case#1, and was finally confirmed by histological evidence of significant IgG4-positive plasma cells infiltration in bone marrow. In case#2, we incidentally observed high uptakes of multi-bone marrow on ¹⁸F-FDG-PET/CT, with the maximum SUV value similar to that of the kidneys, submaxillary glands and hilar, mediastinal lymph nodes by ¹⁸F-FDG-PET/CT. Symptoms and all the hematologic presentation improved rapidly in both patients after steroids initiation. These two cases illustrate the rare bone marrow involvement in active IgG4-RD accompanied by other hematologic syndromes. The significance of disease pathogenesis is worthy of further study.

Diagnostic Dilemma: Cardiorenal Syndrome As an Unusual Presentation of IgG4-Related Disease

IgG4-related kidney disease (IgG4 RKD) is a rare clinical entity characterized by lymphoplasmacytic infiltration rich in IgG4-positive plasma cells along with fibrosis affecting several organs. Tubulointerstitial nephritis is commonly the predominant finding on kidney biopsy. Our patient was admitted with a provisional diagnosis of cardiorenal syndrome of unknown etiology. The patient was dialysis dependent for around 45 days following which kidney biopsy revealed features of acute tubulointerstitial nephritis (ATIN) with IgG4-positive plasma cells and no glomerular involvement. Positron emission tomography-computed tomography was supportive of findings of sialadenitis along with myocarditis. Our patient responded to treatment with steroids with definitive improvement in both renal and cardiac functions. This case highlights the importance of IgG4 RKD as an important differential in patients with ATIN presenting as a clinical syndrome.

PET-Based Imaging with 18F-FDG and 18F-NaF to Assess Inflammation and Microcalcification in Atherosclerosis and Other Vascular and Thrombotic Disorders

Positron emission tomography (PET) imaging with ¹⁸F-fluorodeoxyglucose (FDG) represents a method of detecting and characterizing arterial wall inflammation, with potential applications in the early assessment of vascular disorders such as atherosclerosis. By portraying early-stage molecular changes, FDG-PET findings have previously been shown to correlate with atherosclerosis progression. In addition, recent studies have suggested that microcalcification revealed by ¹⁸F-sodium fluoride (NaF) may be more sensitive at detecting atherogenic changes compared to FDG-PET. In this review, we summarize the roles of FDG and NaF in the assessment of atherosclerosis and discuss the role of global assessment in quantification of the vascular disease burden. Furthermore, we will review the emerging applications of FDG-PET in various vascular disorders, including pulmonary embolism, as well as inflammatory and infectious vascular diseases.

Role of 18 F-FDG PET/CT in Erdheim-Chester Disease in the Era of Multimodality Imaging

Erdheim–Chester disease is a rare disease with systemic non-Langerhans cell histiocytosis, the diagnosis of which with conventional imaging modalities is challenging. We describe a case of a 73-year-old woman who was referred with a progressive history of bilateral proptosis. The magnetic resonance imaging (MRI) orbit demonstrated bilateral orbital masses with optic nerve encasement. A subsequent 18F-FDG PET/CT scan showed multi-organ disease with involvement of the orbits, pericardium, aorta, pararenal fascia, and appendicular bones. Metabolically active, easily accessible areas were selected for CT-guided biopsy. The biopsy showed sheets of foamy histiocytes with the expression of CD 68 and CD 163 consistent with a diagnosis of Erdheim–Chester disease. The FDG PET/CT played a pivotal role in establishing the diagnosis with the assessment of disease extent and further guided in the targeted biopsy.

Abnormal [18F]fluorodeoxyglucose accumulation to tori tubarius in IgG4-related disease

OBJECTIVES

Tubarial glands (TGs) are recently refocused gland tissues localized near the tori tubarius in the nasopharynx and their clinical relevance is not clear yet. IgG4-related disease (IgG4-RD) is a progressive fibrosing condition and salivary glands are well-affected lesions. The aim of the present study is to examine [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) accumulation to the tori tubarius in IgG4-related disease (IgG4-RD).

METHODS

48 patients with IgG4-RD who underwent positron emission tomography (PET) scanning with [¹⁸F]FDG were included and semi-quantitative analysis of [¹⁸F]FDG accumulation to tori tubarius was performed along with the clinical features and histopathological analysis.

RESULTS

Of the 48 patients, abnormal [¹⁸F]FDG accumulation (metabolic tumour volume ≥ 1) to tori tubarius was observed in 15 (31.3%), all of whom had lesions in other head and neck glands. IgG4-RD patients with abnormal [¹⁸F]FDG accumulation to tori tubarius showed swollen nasopharyngeal walls around tori tubarius and forceps biopsy of the lesion revealed acinar cells and IgG4-positive plasma cells histologically. Abnormal [¹⁸F]FDG accumulation (maximum standard uptake value, metabolic tumour volume and total lesion glycolysis) to tori tubarius correlated with higher IgG4 and lower IgA serum concentrations.

CONCLUSIONS

Abnormal [¹⁸F]FDG accumulation to tori tubarius can be observed in patients with IgG4-RD and the abnormal [¹⁸F]FDG accumulation to tori tubarius can be a clue of TG involvement in IgG4-RD.