IgG4-Related Perineural Disease

MR Neurography of the Lumbosacral Plexus: Technique and Disease Patterns

The lumbosacral plexus (LSP) comprises a complex network of nerves supplying the pelvis and lower extremities and may be affected by a wide range of diseases. Lumbosacral plexopathy can be challenging to diagnose due to overlapping clinical presentations and difficulty performing electrodiagnostic testing of the deep pelvic structures. MRI-more specifically, MR neurography (MRN)-can readily depict most LSP segments. MRN techniques, preferably performed at 3.0 T, continue to evolve, with most protocols including two-dimensional and optionally three-dimensional, heavily T2-weighted fat-suppressed sequences. This article provides technical tips for optimizing LSP MRN, as well as an overview of various LSP-related pathologic conditions, with accompanying illustrative examples. ©RSNA, 2025 Supplemental material is available for this article. See the invited commentary by Chhabra in this issue.

Immunoglobulin G4-Related Disease Presenting With Peripheral Neuropathy, Membranous Nephropathy and Interstitial Lung Disease: A Case Report

Immunoglobulin G4-related disease (IgG4-RD) is a chronic, progressive inflammatory disease with fibrosis that affects multiple organs, while symptomatic peripheral nerve invasion is very rare. Here we present a Chinese male aged 77 years with peripheral neuropathy, membranous nephropathy, and interstitial lung disease diagnosed with IgG4-RD. The patient exhibited elevated levels of IgG4 and IgG4/IgG ratios in the blood. A chest computed tomography (CT) showed interstitial pneumonia in both lungs and multiple mediastinal lymphadenopathy. Additionally, electromyography shows neurogenic lesions in both lower extremities and axonal lesions involving motor nerves. Biopsies of the kidney showed membranous nephropathy with numerous IgG4-positive plasma cells. Patients treated with cyclophosphamide and high-dose methylprednisolone showed improvement in neuropathy, proteinuria, and interpulmonary severity. This case demonstrates the unusual presentation of IgG4-RD where peripheral neuropathy is the main feature with multisystem involvement but without mass lesions. It underscores the varied clinical manifestations of this disease.

Electrochemical skin conductance to assess peripheral neuropathy in rheumatic diseases with or without type 2 diabetes using sudoscan

Introduction

Peripheral neuropathy (PN) occurs in diabetes mellitus. However, the association between PN and rheumatic disease (RD) has not been fully investigated. The aim of this study was to assess the prevalence of PN in patients with RDs with or without Diabetes Mellitus.

Methods

A Cross-sectional cohort study, data extracted from patients medical records started in September 2023 to January 2024 in Abu Dhabi, UAE. A Sudoscan machine report was used to assess The electrochemical skin conductance (ESC), Sudomotor dysfunction is evaluated according to the ESC measured on the feet: >60 μS = no dysfunction; 60-40 μS = moderate dysfunction; and <40 μS = severe dysfunction.

Results

Eighty-one patients with RDs, mean age 58 ± 12. There were 55 females (67.9%), and 26 males (32.1%) attended an ambulatory healthcare clinic in Abu Dhabi, UAE. Thirty-three (40.7%) had diabetes, while 48 (59.3%) did not have diabetes. The mean glycated haemoglobin A1c (HBA1c) was 7.4% in diabetic patients and 5.8% in non-diabetic patients Additionally, all patients had a mean blood pressure of 134/72 and a mean Body Mass Index (BMI) of 31.40 kg/m2. Among the study patients, the most common RD was osteoarthritis, which affected 56.8% of the patients. The smallest percentage of patients with PN was found in those with IgG4, at 1.2%. The prevalence of Sudomotor dysfunction (ESC feet: <60 μS) was 72.8% in patients with RDs (all patients diabetic and non-diabetic), while the prevalence of sudomotor dysfunction (ESC feet: <60 μS) in RDs patients with diabetes was 75.8% and 70.8% in RDs patients without diabetes, there was no significant difference between in prevalence of sudomotor dysfunction in RD patients with diabetes compared to RD patients without Diabetes.

Conclusion

Sudomotor dysfunction appears to be common among patients with RD regardless they have diabetes or not. This study recommends screening all RD patients for Sudomotor Dysfunction.

Evaluation of the specificity of trigeminal nerve enlargement in the diagnosis of IgG4-related ophthalmic disease

PURPOSE

Enlargement of the trigeminal nerve is observed in 20-53% of patients with IgG4-related ophthalmic disease (IgG4-ROD) and is known to be a useful finding for the diagnosis of IgG4-ROD. On the other hand, enlargement of the trigeminal nerve has also been found at a certain frequency in orbital lymphoproliferative diseases other than IgG4-ROD. Therefore, we here re-evaluated the specificity of trigeminal nerve enlargement in the diagnosis of IgG4-ROD.

STUDY DESIGN

Retrospective, comparative study.

METHODS

A total of 149 consecutive cases of IgG4-ROD diagnosed at the Department of Ophthalmology, Tokyo Medical University Hospital were studied. As controls, 218 cases of orbital lymphoma, 13 cases of reactive lymphoid hyperplasia (RLH), and 117 cases of benign orbital tumors other than lymphoproliferative diseases were included. Enlargement of the trigeminal nerve (infraorbital or supraorbital nerve) in IgG4-ROD and all the control cases was evaluated on MRI or CT coronal images.

RESULTS

Enlargement of the trigeminal nerve was observed in 35 of the 149 cases (23.5%) of IgG4-ROD and in 7 of the 218 cases (3.2%) of lymphoma, with a significantly highly frequency in IgG4-ROD (P < .0001). No cases of trigeminal nerve enlargement were observed in the cases of RLH or benign orbital tumors. The sensitivity and the specificity of trigeminal nerve enlargement in the diagnosis of IgG4-ROD were 23.5% and 96.8%, respectively. Additionally, enlargement of the trigeminal nerve was significantly more common in men than in women (P < .028).

CONCLUSIONS

The present study indicates that trigeminal nerve enlargement is a characteristic imaging finding and has diagnostic value for IgG4-ROD.

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.

Immunoglobulin G4-related disease manifesting as peripheral neuropathy: A rare clinical symptom due to rare autoimmune disease

Background

Nervous system involvement in immunoglobulin G4-related disease (IgG4-RD) has been rarely reported.

Case Description

We describe an unusual case of IgG4-RD manifested as paresthesia in the right lower extremity. A 51-year-old male presented with paresthesia in the right S1-S3 regions. A neurological examination revealed peripheral neuropathy. Blood examination results were normal, barring slightly elevated IgG levels. Initial magnetic resonance imaging of the swollen right S1 and S2 nerve roots revealed lymphoma, schwannoma, and sarcoidosis. However, following the biopsy, the pathological findings were not typical of these diseases. Abdominal computed tomography revealed perirenal lesions, and IgG4-RD was suspected. The patient had a serum IgG4 level of 724 mg/dL. Additional pathological evaluations of the swollen S1 nerve revealed findings that corresponded to the diagnostic criteria for IgG4-RD. Oral steroid therapy was initiated, which improved paresthesia, and the swollen S1 nerve root gradually shrank.

Conclusion

This report highlights a rare case of IgG4-RD involving nerve roots that neurosurgeons should consider.

Neurosurgical Intervention for Nerve and Muscle Biopsies

(1) Background: Neurologic and musculoskeletal diseases represent a considerable portion of the underlying etiologies responsible for the widely prevalent symptoms of pain, weakness, numbness, and paresthesia. Because of the subjective and often nonspecific nature of these symptoms, different diagnostic modalities have been explored and utilized. (2) Methods: Literature review. (3) Results: Nerve and muscle biopsy remains the gold standard for diagnosing many of the responsible neurological and musculoskeletal conditions. However, the need for invasive tissue sampling is diminishing as more investigations explore alternative diagnostic modalities. Because of this, it is important to explore the current role of neurosurgical intervention for nerve and muscle biopsies and its current relevance in the diagnostic landscape of neurological and musculoskeletal disorders. With consideration of the role of nerve and muscle biopsy, it is also important to explore innovations and emerging techniques for conducting these procedures. This review explores the indications and emerging techniques for neurological intervention for nerve and muscle biopsies. (4) Conclusions: The role of neurosurgical intervention for nerve and muscle biopsy remains relevant in diagnosing many neurological and musculoskeletal disorders. Biopsy is especially relevant as a supportive point of evidence for diagnosis in atypical cases. Additionally, emerging techniques have been explored to guide diagnostics and biopsy, conduct less invasive biopsies, and reduce risks of worsening neurologic function and other symptoms secondary to biopsy.

IgG4-related Orbital Disease Presenting as an Orbital Apex Lesion

IgG4-related disease is an uncommon multisystem inflammatory disease characterized by tissue infiltration by IgG4 plasma cells, extensive fibrosis, and sclerosing inflammation. Diffuse orbital involvement extending to the orbital apex and cavernous sinus has been reported, but a solitary well-circumscribed lesion at the apex has not been previously reported. Herein, we report a unique case of IgG4-related orbital disease presenting as a solitary well-circumscribed orbital apex lesion causing subacute visual decline in a 45-year-old male. MRI demonstrated bilateral lacrimal gland and infraorbital nerve enlargement and an 18 × 7 mm left orbital apex lesion demonstrating homogeneous contrast enhancement and isointense signal on T2. He was initially treated with tapering systemic corticosteroid therapy with improvement in his vision; however, he experienced visual deterioration 3 months later with recurrent inflammation. He subsequently commenced high-dose systemic corticosteroid therapy and rituximab infusions with improvement of left visual acuity to 6/7.5 + 2.

A case of atypical IgG4-related disease presenting hypereosinophilia, polyneuropathy, and liver dysfunction

Ig (immunoglobulin) G4-related disease (Ig4-RD) affects several organs, including salivary glands, lacrimal glands, pancreas, biliary ducts, and retroperitoneum. A 72-year-old woman was examined for hypereosinophilia, high levels of IgG4, polyneuropathy, liver dysfunction, enlargement of lymph nodes and lacrimal glands, and beaded dilation of the bile ducts. We diagnosed Ig4-RD based on biopsies of the lymph nodes, liver, and submandibular gland. The symptoms of the patient improved after glucocorticoid treatment. This was a novel and atypical case of Ig4-RD that was difficult to differentiate from other diseases, including eosinophilic granulomatosis with polyangiitis, idiopathic hypereosinophilic syndrome, and polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, skin changes syndrome. This case report highlights the importance of biopsies in differentiating Ig4-RD.

Case report: Clinical highlights and radiological classification of IgG4-related spinal pachymeningitis: A rare case series and updated review of the literature

PURPOSE

Hypertrophic pachymeningitis associated with immunoglobulin G4-related disease (IgG4-RD) has been rarely reported, and there is little information and no clear consensus on the management of IgG4-related spinal pachymeningitis (IgG4-RSP). The present study described its possible clinical features, including the symptoms, imaging, treatment and prognosis of patients with IgG4-RSP.

METHODS

We report three patients who presented with progressive neurological dysfunction due to spinal cord compression. Relevant articles were searched from the PubMed, Web of Science, and Embase databases, and the resulting literature was reviewed.

RESULTS

The literature review provided a summary of 45 available cases, which included three cases from our center. Progressive worsening of neurological impairment was observed in 22 patients (48.9%). The lesions involved the thoracic spine (n=28, 62.2%), cervical spine (n=26, 57.8%), lumbar spine (n=9, 20.0%), and sacral spine (n=1, 2.2%). Furthermore, the lesions were located in the dura mater (n=18, 40.0%), epidural space (n=17, 37.8%), intradural-extramedullary space (n=9, 20.0%), and intramedullary space (n=1, 2.2%). On magnetic resonance imaging (MRI), the lesions generally appeared as striated, fusiform, or less often lobulated oval changes, with homogeneous (n=17,44.7%) and dorsal (n=15,39.5%) patterns being the most common. Thirty-five patients had homogeneous T1 gadolinium enhancement. Early surgical decompression, corticosteroid treatment, and steroid-sparing agents offered significant therapeutic advantages. A good therapeutic response to disease recurrence was observed with the medication.

CONCLUSION

The number of reported cases of IgG4-RSP remains limited, and patients often have progressive worsening of their neurological symptoms. The features of masses identified on the MRI should be considered. The prognosis was better with decompression surgery combined with immunosuppressive therapy. Long-term corticosteroid treatment and steroid-sparing agent maintenance therapy should be ensured. A systemic examination is recommended to identify the presence of other pathologies.

Ultrasonography of IgG4-related dacryoadenitis and sialadenitis: Imaging features and clinical usefulness

OBJECTIVES

To clarify the ultrasonographic features of immunoglobulin G4 (IgG4)-related dacryoadenitis and sialadenitis (IgG4-DS) and their usefulness in clinical diagnostic sessions.

METHODS

By re-evaluating 96 consecutive patients with IgG4-related disease, we identified 54 patients (male:female = 37:17; median age, 69.5 years) who underwent lacrimal or submandibular gland (LG or SG, respectively) ultrasonography and computed tomography (CT). Their clinical and ultrasonographic features were retrospectively analysed. Radio-pathological correlations were also examined in LG (23 cases) and SG lesions (20 cases). Additionally, the diagnostic accuracy of CT for LG/SG lesions was evaluated.

RESULTS

Abnormal ultrasonographic findings were detected in 33 (LGs) and 38 (SGs) patients, and most of them were observed bilaterally. All lesions were well demarcated and demonstrated diffuse low-echoic areas (rocky pattern) or multiple low-echoic nodules surrounded by high-echoic linear shadows (cobblestone pattern) corresponding to intra-lobular inflammation and inter-lobular fibrosis. Moreover, 42% (LGs; 14/33) and 42% (SGs; 16/38) patients had glandular lesions without clinical symptoms associated with the affected glands. The diagnostic accuracy of CT was ∼80% for LG and 55% for SG.

CONCLUSIONS

Ultrasonographic findings in IgG4-DS included diffuse or nodular low-echoic areas with linear high-echoic structures corresponding to inflamed lobules and inter-lobular fibrosis. These findings can help detect IgG4-DS.

Nerve biopsy: Current indications and decision tools

After initial investigation of patients presenting with symptoms suggestive of neuropathy, a clinical decision is made for a minority of patients to undergo further assessment with nerve biopsy. Many nerve biopsies do not demonstrate a definitive pathological diagnosis and there is considerable cost and morbidity associated with the procedure. This highlights the need for appropriate selection of patients, nerves and neuropathology techniques. Additionally, concomitant muscle and skin biopsies may improve the diagnostic yield in some cases. Several advances have been made in diagnostics in recent years, particularly in genomics. The indications for nerve biopsy have consequently changed over time. This review explores the current indications for nerve biopsies and some of the issues surrounding its use. Also included are comments on alternative diagnostic modalities that may help to supplant or reduce the use of nerve biopsy as a diagnostic test. These primarily include extraneural biopsy and neuroimaging techniques such as magnetic resonance neurography and nerve ultrasound. Finally, we propose an algorithm to assist in deciding when to perform nerve biopsies.

Immunoglobulin G4-related Disease Accompanied by Peripheral Neuropathy: A Report of Two Cases

Due to its rarity and the limited literature, the clinicopathological characteristics of peripheral nerve involvement in immunoglobulin G4 (IgG4)-related disease are unknown. We present two cases of IgG4-related disease, accompanied by peripheral neuropathy, presenting as unilateral ptosis (case 1) and sclerosing cholangitis (case 2), respectively. In both cases, sural nerve biopsy indicated vasculitis as the underlying pathophysiology; the peripheral neuropathy was refractory to corticosteroid therapy. In contrast to the previously proposed pathomechanism of IgG4-related neuropathy (direct lymphoplasmacytic infiltration), the pathological findings in our cases suggest that vasculitis occurs secondary to systemic autoimmune conditions.

Involvement of Multiple Trigeminal Nerve Branches in IgG4-Related Orbital Disease

PURPOSE

To describe the occurrence of multiple trigeminal nerves (TGNs) enlargement in patients with orbital IgG4-related disease.

METHODS

Retrospective review of MRI findings and medical records of 6 patients (10 orbits) with orbital IgG4-related disease and enlargement of more than 1 TGN. Orbital biopsies were performed in all cases revealing the typical lymphoplasmacytic infiltrate with significant plasma cell positivity for IgG4 (IgG4+/IgG ratio ≥ 40%). Three experienced neuroradiologists reviewed the MRI sequences using a digital imaging viewer system (Horos, https://horosproject.org/).

RESULTS

Bilateral involvement of at least 2 TGNs divisions was detected in all 6 patients. Enlargement of both V1 and V2 nerves was diagnosed in 5 patients, and in 3 cases, all TGN divisions were involved. V2 nerves were the most affected. In this division, all 12 infraorbital nerves were enlarged, followed by lesser palatines (10/83.3%), superior alveolar (10/83.3%), and zygomatic (6/50%). V1 and V3 nerves were less affected albeit 9 (75%) frontal branches (V1), and 50% of the inferior alveolar (V3) nerves were also enlarged.

CONCLUSIONS

Widespread involvement of the TGN is an important feature of IgG4-related disease.

The neurology of IGG4-related disease

PURPOSE OF REVIEW

IgG4-related disease (IgG4-RD) is emerging as a fibro-inflammatory entity affecting multiple organs, including manifold neurologic manifestations. This review discusses general characteristics of IgG4-RD neurologic disease including epidemiology, histology, clinical picture and treatment approaches.

RECENT FINDINGS

IgG4-RD is increasingly recognized as an important underlying pathophysiology in multiple disorders of neurologic interest, including orbital inflammation, infundibulo-hypophysitis, hypertrophic pachymeningitis, and even in rare cases CNS parenchymal disease and cranial vascular involvement. These were previously considered idiopathic and unrelated to any systemic disease but now known to share a common histopathology. New knowledge regarding the pathogenesis, clinical features and epidemiology of IgG4 is emerging, and new neurological manifestations continue to be described. Diagnostic progress includes CT-PET imaging, the use of flow cytometry for plasmablast quantification, and the use of reverse passive latex agglutination aiming to overcome the prozone phenomenon. Histopathologic confirmation of IgG4-RD remains the gold standard method of diagnosis but new diagnostic criteria for systemic and organ-specific disease are being proposed. Though glucorticoids remain the mainstay of therapy, relapses and incomplete recovery are frequent. Rituximab is a promising treatment in IgG4-RD that is severe, refractory or glucocorticoid dependent. Initiation of immunosuppression at an early stage of disease should be considered in order to avoid development of refractory fibrosis.

SUMMARY

The current review emphasizes the neurologic manifestations of IgG4-RD.

Immunoglobulin G4-related disease presenting with peripheral neuropathy: a case report

Background

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibro-inflammatory condition characterized by high serum IgG4 concentrations and tissue infiltration by IgG4-positive plasma cells. Reports have demonstrated that IgG4-RD affects various organs, including the pancreas, kidney, lung, thyroid, and lacrimal and salivary glands. In the nervous system, hypertrophic pachymeningitis and hypophysitis are mainly related to IgG4-RD; however, the peripheral neuropathy involvement is unusual.

Case presentation

We report on a 69-year-old woman with multiple mononeuropathy, weight loss and kidney mass in the setting of IgG4-RD. Biopsies of the kidney mass showed lymphoplasmacytic sclerosing inflammation with numerous IgG4-positive plasma cells. IgG4 and IgG4/IgG ratios in the blood were elevated. The patient was treated with high dose methylprednisolone with improvement in her neuropathy.

Conclusions

IgG4-RD is a relatively recently reported systemic fibrous inflammatory disease caused by the infiltration of IgG4-positive plasma cells in various organs. In the nervous system, symptomatic peripheral nerve invasion is very rare. However, as demonstrated in our case, IgG4-RD may present with primarily peripheral nerve disease.

Imaging of IgG4-related disease in the extracranial head and neck

PURPOSE

Immunoglobulin G4-related disease (IgG4-RD) is a newly defined fibro-inflammatory multisystemic condition defined by a triad of diagnostic criteria based on clinical presentation, biochemical and histopathological findings. Whereas some subsites of this disease have been well described in the literature so far (e.g. pancreas, kidneys, retroperitoneum, salivary glands), more recently identified anatomical sites of involvement in the head and neck are less well understood (e.g. nose, paranasal sinuses).

METHOD

This pictorial review details the imaging appearances of extracranial IgG4-RD in the Head & Neck. Multimodality imaging appearance and features are presented, with reference to the published literature to date.

RESULTS

Following a subsite-based approach, we present both the most common and the more rarely encountered imaging patterns of IgG4-RD in the extracranial head and neck, along with the relevant differential diagnoses to consider. Our institutional experience not only cements what is already known in the existing literature on this topic, but also reveals new imaging features of IgG4-RD, notably in the sinonasal tract.

CONCLUSIONS

This pictorial review of extracranial head & neck IgG4-RD will enable radiologists to recognise the features of this condition and propose it as a differential diagnosis to include alongside other probable entities. It establishes the place of the radiologist in the diagnosis and management of IgG4-RD.

Immunoglobulin G4-Related Orbital Disease with Bilateral Optic Perineuritis and Maxillary Nerves Involvement: A Case Report

Immunoglobulin G4-related optic neuropathy caused by optic perineuritis is a rare complication of immunoglobulin G4-related disease (IgG4-RD). Herein, we report a 38-year-old Asian man with history of sinusitis who presented with painless blurred vision and proptosis for over 6 months. Examination with the Hertel exophthalmometer revealed 21.5 mm on both eyes. Magnetic resonance imaging revealed a doughnut sign encircling the right optic nerve, bilateral tram-track signs on both optic nerves, enlarged bilateral maxillary nerves with perineural spreading to the infraorbital nerves, hypertrophy of extraocular muscles, and pansinusitis. Visual evoked potentials displayed bilateral delayed P100 latency, indicating bilateral optic neuropathy. Biopsy with functional endoscopic sinus surgery demonstrated diffuse dense lymphoplasmacytic infiltrate and fibrosis. IgG4-positive plasma cells exceeded 50 cells per high-power field while the overall IgG4/IgG ratio was above 40%. Serological studies unveiled extremely high serum concentrations of IgG4 (2650 mg/dL), and the calculated serum IgG4/IgG ratio was 100%. These comprehensive features supported the diagnosis of IgG4-RD with bilateral optic perineuritis, branches of trigeminal nerve involvement, and pansinusitis. The visual acuity improved slightly following the initiation of treatment with corticosteroids, but it became worse again during the tapering course. Following another course of corticosteroids followed by subsequent immunosuppressant treatment with azathioprine, vision in both eyes ultimately improved during the 2-year follow-up period.

Autoimmune pancreatitis: an update

OBJECTIVE

Since the time of inception of autoimmune pancreatitis (AIP), our knowledge of autoimmune pancreatitis has expanded significantly. The aim of this review is to provide an update on clinical manifestations, diagnosis, imaging features, and treatment of AIP.

BACKGROUND AND CLINICAL SIGNIFICANCE

Type 1 AIP is the pancreatic manifestation of IgG4-related systemic disease, which can be diagnosed using a combination of clinical, histopathological, pancreatic imaging findings in conjunction with manifestation in other organs, as well of responsiveness to steroid treatment. It is vital to differentiate AIP from pancreatic cancer since both can mimic each other clinically and radiologically. Type 2 AIP is a rare but distinct subtype of AIP which occurs mostly in the younger patient.

CONCLUSION

AIP is steroid-responsive chronic pancreatitis with distinct manifestations on imaging.

Diagnostic imaging guide for autoimmune pancreatitis

The International Consensus Diagnosis Criteria for autoimmune pancreatitis (AIP) has been published internationally for the diagnosis of AIP. However, since the revisions in 2006 and 2011, the Clinical Diagnostic Criteria for Autoimmune Pancreatitis 2018 have been published. The criteria were revised based the Clinical Diagnostic Criteria 2011, and included descriptions of characteristic imaging findings such as (1) pancreatic enlargement and (2) distinctive narrowing of the main pancreatic duct. In addition, pancreatic duct images obtained by magnetic resonance cholangiopancreatography as well as conventional endoscopic retrograde pancreatography were newly adopted. The guideline explains some characteristic imaging findings, but does not contain descriptions of the imaging methods, such as detailed imaging parameters and optimal timings of dynamic contrast-enhanced computed tomography/magnetic resonance imaging. It is a matter of concern that imaging methods can vary from hospital to hospital. Although other characteristic findings have been reported, these findings were not described in the guideline. The present paper describes the imaging methods for obtaining optimal images and the characteristic imaging findings with the aim of standardizing image quality and improving diagnostic accuracy when radiologists diagnose AIP in actual clinical settings.

[Optic neuropathy from connected intra- and extraorbital lesions in IgG4-related disease]

We present the case of a 74-year-old woman complaining of blurred vision in the left eye who was found to have a unilateral, continuous lesion of the optic nerve and nerve sheath accompanied by an intracranial mass next to the cavernous sinus and meninges. Surgical decompression of the left optic nerve in the optic canal and partial resection of the mass followed by prednisolone administration were successful. Immunohistochemical analysis disclosed abundant infiltration of IgG4-positive plasma cells at >10 cells/high power field. These findings indicated a new pattern of compressive optic neuropathy with confirmed IgG4 histopathological findings. Such an extensive lesion may produce visual disturbance.

Orbital IgG4 Disease: Imaging Findings on 68Ga-DOTANOC PET/CT

Immunoglobulin G4 (IgG4)-related diseases are a spectrum of systemic inflammatory conditions of unknown etiology, which are characterized by infiltration of tissues by IgG4 plasma cells and sclerosing inflammation (Cheuk and Chan Adv Anat Pathol 17:303-32, 2010). Although this condition was initially described in relation to autoimmune pancreatitis, now it has been reported in almost every organ system of body (Zen and Nakanuma Am J Surg Pathol 34:1812-9, 2010, Masaki et al. Ann Rheuma Dis 68:1310-5, 2009). Orbital involvement by IgG4 disease can involve extraocular muscles (EOM), lacrimal glands, conjunctiva, eyelids, infraorbital nerve, orbital fat, and nasolacrimal system (McNab and McKelvie. Ophthal Plast Reconstr Surg 31:167-78, 2015, Katsura et al. Neuroradiology 54:873-82, 2012). The basis of using ⁶⁸Ga-DOTANOC PET/CT in IgG4 orbital disease is the known expression of somatostatin receptors in chronic inflammatory cells (Cuccurullo et al. Indian J Radiol Imaging 27:509-16, 2017) and also avidity shown previously in other IgG4-related diseases (Cheng et al. Clin Nucl Med 43:773-6, 2018).

IgG4-related disease of the central and peripheral nervous systems

IgG4-related disease can involve nearly any organ system, including the central and peripheral nervous systems. The pathology findings are consistent from organ to organ, but careful clinicopathological correlation is necessary to establish the diagnosis. Many non-neurological and neurological inflammatory conditions, previously regarded as idiopathic in nature, are now recognised to fall within the spectrum of IgG4-related disease. The condition is highly treatable, but probably remains substantially under-recognised. In this Review, we offer an important and timely update on the current and emerging aspects of this neurological disease. Following a short overview of IgG4-related disease, we describe the current understanding of neurological findings, pathophysiology, approaches to diagnosis, and treatment of IgG4-related disease affecting the central and peripheral nervous systems.

Autoimmune Pancreatitis

Over the course of the last 2 decades our knowledge of autoimmune pancreatitis has increased exponentially. In this review, we summarize the clinical presentation, diagnosis and treatment of AIP, to better allow general gastroenterologists and primary care providers to consider AIP as a as a rare but important cause of painless obstructive jaundice and recurrent acute pancreatitis. While steroids remain the mainstay of first line therapy, a number of patients with type 1 AIP require immunomodulators or rituximab to maintain remission; recommendations on the management of relapses continue to evolve.

Imaging of IgG4-related disease of the head and neck

IgG4-related disease is a systemic, inflammatory disorder typically involving multiple organ systems. Several eponymous conditions described previously in the clinical and radiology literature are now recognised to be part of the IgG4-related disease spectrum. This includes multiple manifestations in the head and neck region, which are the subject of this review. Imaging can occasionally suggest the specific diagnosis of IgG4 disease. More commonly, it will be included in a limited differential diagnosis that requires clarification with the aid of image-guided biopsy. There are strict histopathological criteria for the diagnosis of IgG4-related disease.

Neurological Manifestations of IgG4-Related Disease

OPINION STATEMENT

IgG4-related disease (IgG4-RD) is a multisystem inflammatory disorder. Early recognition of IgG4-RD is important to avoid permanent organ dysfunction and disability. Neurological involvement by IgG4-RD is relatively uncommon, but well recognised-hypertrophic pachymeningitis and hypophysitis are the most frequent manifestations. Although the nervous system may be involved in isolation, this more frequently occurs in conjunction with involvement of other systems. Elevated circulating levels of IgG4 are suggestive of the condition, but these are not pathognomonic and exclusion of other inflammatory disorders including vasculitis is required. Wherever possible, a tissue diagnosis should be established. The characteristic histopathological changes include a lymphoplasmacytoid infiltrate, storiform fibrosis and obliterative phlebitis. IgG4-RD typically responds well to treatment with glucocorticoids, although relapse is relatively common and treatment with a steroid-sparing agent or rituximab may be required. Improved understanding of the pathogenesis of IgG4-RD is likely to lead to the development of more specific disease treatments in the future.

Is MuSK myasthenia gravis linked to IgG4-related disease?

Immunoglobulin (Ig) G4-related disease (IgG4-RD) is an immune-mediated inflammatory condition that affects a wide variety of sites, including the nervous system, where it can involve the meninges or the pituitary gland, and cause perineural mass lesions. A large subset of acetylcholine receptor antibody (Ab)-negative myasthenia gravis (MG) patients has muscle-specific tyrosine kinase (MuSK) Abs, generally of the IgG4 subclass. There has not been any association found between IgG4-RD and MuSK MG yet. We report the first case of MuSK MG associated with lymphadenopathy with histopathology consistent with IgG4-RD. A 54-year-old woman with MuSK MG developed eight compression fractures related to steroid therapy. Eighteen months after initial presentation she was found to have retroperitoneal lymphadenopathy with biopsy findings consistent with IgG4-RD. She was started on rituximab with clinical improvement and ability to taper immunomodulatory agents for the first time. Our case raises number of questions regarding a potential link between MuSK MG and IgG4-RD which may shed further light on the pathophysiology and management of these diseases.

Infraorbital nerve involvement on magnetic resonance imaging in European patients with IgG4-related ophthalmic disease: a specific sign

OBJECTIVES

To measure the frequency of infraorbital nerve enlargement (IONE) on magnetic resonance imaging (MRI) in European patients suffering from an IgG4-related ophthalmic disease (IgG4-ROD) as compared to patients suffering from non-IgG4-related ophthalmic disease (non-IgG4-ROD).

METHODS

From January 2006 through April 2015, 132 patients were admitted for non-lymphoma, non-thyroid-related orbital inflammation. Thirty-eight had both pre-therapeutic orbital MRI and histopathological IgG4 immunostaining. Fifteen patients were classified as cases of IgG4-ROD and 23 patients as cases of non-IgG4-ROD. Two readers performed blinded analyses of MRI images. The main criterion was the presence of an IONE, defined as the infraorbital nerve diameter being greater than the optic nerve diameter in the coronal section.

RESULTS

IONE was present in 53% (8/15) of IgG4-ROD cases whereas it was never present (0/23) in cases of non-IgG4-ROD (P < 0.0001). IONE was only present in cases where, on MRI, the inflammation of the inferior quadrant was present and in direct contact with the ION canal.

CONCLUSIONS

In European patients suffering from orbital inflammation, the presence of IONE on an MRI is a specific sign of IgG4-ROD. Recognition of this pattern may facilitate the accurate diagnosis for clinicians and allow for the adequate management and appropriate care of their patients.

KEY POINTS

• IONE on an MRI is a specific sign of IgG4-ROD. • IONE recognition allows for a quicker diagnosis and appropriate management. • IONE appears when inflammation is in direct contact with the ION canal.

Therapeutic approach to IgG4-related disease: A systematic review

To review the reported evidence on the therapeutic management of IgG4-related disease (IgG4-RD) in clinical practice.A systematic search of the literature was conducted. The primary outcome measured was the rate of efficacy of first-line therapeutic approaches. Secondary outcomes measured included the rate of disease relapse, the outcome of untreated patients, the rate of patients without drug therapy at the end of follow-up, the rate of side effects, and mortality. The MOOSE, AHRQ, STROBE, and GRACE recommendations/statements were followed.The results of the systematic search strategy yielded 62 studies that included a total of 3034 patients. Complete information about first-line therapeutic regimens was detailed in 1952 patients, including glucocorticoid-based regimens in 1437 (74%), drug-free regimens in 213 (11%), and other therapies in 38 (2%). No therapy (wait and see management) was reported in 264 (13%) patients. The efficacy of monotherapy with glucocorticoids was specified in 1220 patients, of whom 97% had a therapeutic response. Relapses, however, were reported in 464/1395 (33%) patients despite typically short follow-up periods. Therapeutic efficacy was reported in 219/231 (95%) of relapses treated with glucocorticoids, 56/69 (81%) of those treated with azathioprine, 16/22 (72%) of those treated with other immunosuppressive agents, and in the 9 cases treated with rituximab (100%). In 14 studies, the authors detailed the outcome of 159/246 patients with wait-and-see management; spontaneous improvement or resolution was reported in 68 (43%) cases. Wide heterogeneity was observed with respect to the first-line therapeutic approaches used for the different organ-specific disease subsets, including significant differences in the mean dose of glucocorticoids used.Nearly 70% of reported IgG4-RD patients are treated with oral glucocorticoids in monotherapy. However, the therapeutic management is heavily influenced by geographical, epidemiological, and clinical factors, especially with respect to the predominant organ affected. The frequency of glucocorticoid failure to induce sustained remissions both during and after treatment and the assessment of glucocorticoid toxicity in IgG4-RD require further study.

Immunoglobulin G4-related disease of the orbital cavity, cervical lymph nodes and greater auricular nerve: case report

IgG4-related disease (IgG4-RD) is a novel clinicopathological entity characterised by elevated tissue levels of IgG4-positive plasma cells. It can present in almost every organ systems. We present a case of a 48year-old man with recurrent intra-orbital and cervical lymph node swelling and found to have greater auricular nerve involvement intraoperatively during open surgical biopsy. Histopathological evaluation of biopsied specimens from these lesions yielded IgG4-positive plasma cell infiltration on immunohistochemistry. Key pathological features such as prominent lymphoplasmacytic population, storiform fibrosis and obliterative phlebitis were also seen. A diagnosis of IgG4-RD was made. Oral prednisone therapy ameliorated the symptoms and patient remained in remission at followup. Literature review indicated that IgG4-RD is a rare condition that seldom occurs concurrently in the orbital cavity, cervical lymph nodes and involving the greater auricular nerve. The condition may often masquerade as malignancy or infection due to formation of tumefactive lesions but tend to respond favourably to glucocorticoid or immunosuppressants. The differential diagnosis of unusual mass lesions in these locations should include IgG4-RD. The otolaryngologist, as well as other health professionals, should be familiar with this novel disease to ensure timely diagnosis and treatment.

A case of refractory IgG4-related peripheral neuropathy with severe axonal damage

A 78-year-old man presented complaining of tingling and pain. Neurological examination revealed dysesthesia and hypothermesthesia below both knees and areflexia in the lower extremities. Laboratory data revealed elevated serum levels of immunoglobulin IgG4 and para-aortic, and mesenteric lymphadenopathy was evident on plain computed tomography of the abdomen. Microscopic findings of a bone marrow biopsy specimen showed occlusion of blood vessels with IgG4-positive plasma cells. IgG4-related disease was diagnosed because the bone marrow biopsy exhibited > 10 IgG4-positive plasma cells per high-power field. Treatment was initiated with prednisolone starting at 30 mg/day, but no improvement in neurological symptoms was achieved. Sural nerve biopsy demonstrated obstructive thromboangiitis with severe loss of myelin and axons. Further investigations are needed to elucidate the relationship between obstructive thromboangiitis and steroid-resistant IgG4-related peripheral neuropathy.

IgG4-Related Neuromyopathy Associated With Recurrent Pleural Effusion

OBJECTIVE

Immunoglobulin G4-related disease (IgG4-RD) is an increasingly recognized idiopathic systemic disorder associated with elevated serum IgG4 level and tissue infiltration by IgG4-positive plasma cells. Multiple neurological manifestations, including peripheral neuropathy, have been described in IgG4-RD. Our objective is to discuss a case report and review of the literature, which would expand the spectrum of IgG4-RD.

METHODS

We describe the clinical features and biopsy findings in a patient with IgG4-RD who presented with features suggestive of neuromyopathy in the setting of recurrent pleural effusion and weight loss.

RESULTS

Electrodiagnostic findings were suggestive of an irritable myopathy and polyradiculoneuropathy with primary demyelination and secondary axonal degeneration. Pleural biopsy and laboratory studies confirmed the diagnosis. Improvement was sustained with steroid therapy.

CONCLUSIONS

We describe the first case, to our knowledge, of IgG4-related neuromyopathy associated with recurrent pleural effusion. Our case expands the clinical spectrum of IgG4-RD. Neurologists should be aware of this treatable disorder and in the appropriate clinical context consider it in the differential diagnosis of neuromyopathy.

IgG4-Related Sialoadenitis with a Skin Lesion and Multiple Mononeuropathies Suggesting Coexistent Cryoglobulinemic Vasculitis

A 68-year-old man was admitted because of weakness of the left leg, dysesthesiae of the extremities and bilateral lower extremity purpura. A neurological examination showed mononeuritis multiplex with laboratory evidence of hypocomplementemia, cryoglobulinemia and leukocytoclastic vasculitis in the biopsy of a skin specimen. The patient also exhibited bilateral submandibular gland swelling, elevated serum IgG4 levels and infiltration of a large number of IgG4-positive plasma cells in the submandibular glands. These findings were consistent with both cryoglobulinemic vasculitis and IgG4-related disease. The administration of oral prednisolone (1 mg/kg/day) resolved the neurological manifestations and the swelling of the submandibular glands and cryoglobulinemia.

The many facets of dacryoadenitis

PURPOSE OF REVIEW

To review the spectrum of lacrimal gland inflammation, with particular reference to the old condition, idiopathic dacryoadenitis, and the new, immunoglobulin G4 (IgG4)-related dacryoadenitis.

RECENT FINDINGS

Idiopathic dacryoadenitis remains the most common inflammatory lesion of the lacrimal gland, for which surgical treatment is successful. There is mounting evidence that the presence of IgG4-positive plasma cells in a lacrimal gland specimen is nonspecific, for being found in other inflammatory lacrimal gland lesions, even lymphoproliferative ones. To identify IgG4-related dacryoadenitis, particularly when there is no documented disease elsewhere, the criteria have been strengthened toward abundant IgG4-positive plasma cell counting.

SUMMARY

The gold standard of diagnosis of noninfectious lacrimal gland inflammation is tissue biopsying, which is commonly therapeutic in the case of idiopathic dacryoadenitis. Although it was initially suggested that IgG4-related dacryoadenitis is a possible cause of idiopathic dacryoadenitis, it becomes obvious that it has more resemblance to the lymphoproliferative tumors.

[Clinicopathological features of neuropathy associated with IgG4-related disease]

The newly recognized entity IgG4-related disease (IgG4-RD) is characterized by an elevated IgG4 serum concentration, swelling of organ, and tissue infiltration by IgG4-positive plasma cells with fibrosis. IgG4-RD has been reported in various organs. In the field of neurology, hypophysitis and hypertrophic pachymeningitis have been known to be related to IgG4-RD, while reported patients with neuropathy manifesting features compatible to IgG4-RD. The features of IgG4-related neuropathy are characterized by sensory-motor neuropathy, mononeuritis multiplex pattern, and predominant involvement of distal portions of the lower extremities. In the sural nerve biopsy specimens, fibrosis and IgG4-positive plasma cell infiltration in the epineurium and decreased myelinated fiber density due to axonal degeneration were observed. IgG4-RD should be considered as the differential diagnosis of neuropathy.

IgG4-Related Ophthalmic Disease: Pooling of Published Cases and Literature Review

In recent years, IgG4-related ophthalmic disease (IgG4-ROD) has emerged as a common cause of orbital inflammation, accounting for a substantial proportion of idiopathic orbital inflammation and lymphoid hyperplasia. The last pooled analysis of published cases was conducted in 2012, but a large number of new cases have been added to the literature since then. In this review, we present the demographic, clinical, histological, and treatment data for 172 published cases of biopsy-confirmed IgG4-ROD. Results are accompanied by a review of the relevant literature.

Diagnostic Approach to the Complexity of IgG4-Related Disease

IgG4-related disease (IgG4-RD) is a systemic disease characterized by the infiltration of IgG4-bearing plasma cells and, more importantly, distinctive histopathological features: storiform fibrosis, obliterative phlebitis, a lymphoplasmacytic infiltrate, and mild-to-moderate tissue eosinophilia. The diagnostic approach is complex and relies on the coexistence of various clinical, laboratory, and histopathological findings, none of which is pathognomonic in and of itself. IgG4-related disease should be suspected in patients presenting with unexplained enlargement or swelling of 1 or more organs or tissue organs. Four laboratory abnormalities often provide initial clues to the diagnosis of IgG4-RD: peripheral eosinophilia, hypergammaglobulinemia, elevated serum IgE levels, and hypocomplementemia. Elevated serum IgG4 levels provided critical information in identifying the first cases of IgG4-RD, but recent studies have reported substantial limitations to the measurement of serum IgG4 concentrations, precluding reliance on serum IgG4 concentrations for diagnostic purposes. In contrast, new studies have suggested a promising role of flow cytometry studies in the diagnosis and longitudinal management of IgG4-RD. Demonstration of the classic histopathological features of IgG4-RD remains crucial to diagnosis in most cases, and biopsy proof is preferred strongly by most disease experts before the initiation of treatment. Of note, the multiorgan nature of IgG4-RD was first established in 2003. This review intends to provide most recent knowledge about the clinical, laboratory, radiological, and pathological characteristics of IgG4-RD that may guide the physician to establish an early diagnosis. We searched PubMed and MEDLINE for relevant articles published between January 1, 2000, and November 1, 2014, using the search terms IgG4 and IgG4-related.

Immunology of IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition that derives its name from the characteristic finding of abundant IgG4(+) plasma cells in affected tissues, as well as the presence of elevated serum IgG4 concentrations in many patients. In contrast to fibrotic disorders, such as systemic sclerosis or idiopathic pulmonary fibrosis in which the tissues fibrosis has remained largely intractable to treatment, many IgG4-RD patients appear to have a condition in which the collagen deposition is reversible. The mechanisms underlying this peculiar feature remain unknown, but the remarkable efficacy of B cell depletion in these patients supports an important pathogenic role of B cell/T cell collaboration. In particular, aberrant T helper type 2 (Th2)/regulatory T cells sustained by putative autoreactive B cells have been proposed to drive collagen deposition through the production of profibrotic cytokines, but definitive demonstrations of this hypothesis are lacking. Indeed, a number of unsolved questions need to be addressed in order to fully understand the pathogenesis of IgG4-RD. These include the identification of an antigenic trigger(s), the implications (if any) of IgG4 antibodies for pathophysiology and the precise immunological mechanisms leading to fibrosis. Recent investigations have also raised the possibility that innate immunity might precede adaptive immunity, thus further complicating the pathological scenario. Here, we aim to review the most recent insights on the immunology of IgG4-RD, focusing on the relative contribution of innate and adaptive immune responses to the full pathological phenotype of this fibrotic condition. Clinical, histological and therapeutic features are also addressed.