The great mimicker: IgG4-related disease

Laboratory characteristics of IgG4-related disease: A retrospective study from a single tertiary medical center

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition with unique histopathological features that can affect most organs, making diagnosis challenging. This study characterized detailed laboratory characteristics of IgG4-RD. Baseline clinical and laboratory features of 33 patients with IgG4-RD were reviewed, including serum IgG4 concentrations, serum free light chains (sFLCs), IgGĸ- and IgGλ-heavy/light chains (HLCs), capillary serum protein electrophoresis (SPE), and immunofixation electrophoresis (IFE) of IgG4 subclass. The cohort of 33 patients showed male predominance (94%), with 8 (24%) exhibiting multiple organ involvement. Most patients (88%) had an elevated IgG4 concentration, and 67% had elevated erythrocyte sedimentation rate and IgE levels. Median IgG4 concentration at baseline was significantly higher in patients with >2 organs involved than those with ≤2. Furthermore, erythrocyte sedimentation rate was significantly correlated with serum IgG4 concentrations at baseline. SPE results demonstrated polyclonal gammopathy in most patients. Half of the patients had an increased κ/λ sFLC ratio, 42% had an increased IgGκ/IgGλ HLC ratio. Most patients exhibited hypergammaglobulinemia in the anodal end of the ɤ region on SPE. This study describes detailed laboratory features of IgG4-RD. Although none of these tests are considered diagnostically sufficient by itself, the provided laboratory characteristics can increase awareness of this disorder and help distinguish it from other IgG4-RD mimics.

[IgG4-related disease: about 3 cases]

IgG4-Related disease (IgG4-RD), formerly known as IgG4-related autoimmune polyexocrinopathy, is a new condition including Plasminogen Activator Inhibitor-1 (PAI-1). It can affect different organs (central nervous system, salivary glands, thyroid, lungs, pancreas, bile ducts, liver, digestive tract, kidneys, prostate, etc.) with symptoms depending on the organ that is affected. It is more common in men older than 50 years of age. Its incidence and prevalence are poorly known because it is an uncommon disease. It is most common in Asia, accounting for only 20-30% of PAI in the Western world. Diagnosis is based on histological examination which shows dense lymphoplasmocytic infiltration in the organ affected associated with IgG4-positive plasma cells (immunohistochemistry), organ fibrosis and obliterating venulitis, all this in the context of increased serum IgG4 levels in more than 80% of cases. Patients are sensitive to corticosteroid therapy, with a high risk of relapse after discontinuation of corticosteroid therapy. This leads to the use of immunomodulators, mainly: thiopurines (azathioprine or 6-mercaptopurine), methotrexate and more recently rituximab, which can also be used as induction therapy. Given recent advances, accurate histological and clinical criteria are currently known to limit inappropriate management such as surgery. However, knowledge gaps remain concerning: pathophysiology, identification of specific biomarkers other than IgG4, natural history of the disease and long-term cancer risk assessment, performances of diagnostic tools such as endoscopic ultrasound-guided pancreatic biopsy. As well, consensual international management should be defined in the early stages of the disease and when patients develop recurrences. The purpose of this study was to report 3 cases of IgG4-Related disease on the basis of clinical and radiological criteria as well as therapeutic response.

Retrospective single-centre analysis of IgG4-related disease patient population and treatment outcomes between 2007 and 2017

Objective

The aim was to gain a better understanding of the prevalence, organ involvement, clinical characteristics and long-term outcomes of medical and surgical treatments of IgG4-related disease (IgG4-RD).

Methods

Query of the Cleveland Clinic pathology database for IgG4 plasma cell staining between 2007 and 2017 yielded 1481 results, of which 57 cases were identified as highly likely (n = 28; 49%) or probable (n = 29; 51%) IgG4-RD by histopathological criteria and IgG4 serum concentrations. Patient demographics, type of treatment and outcomes were retrieved from medical records. Patients were designated as being in remission if indicated in the chart and/or symptom- and objective finding-free for >6 months, relapsed if symptoms/findings recurred after remission, active if no remission was achieved during follow-up, and as unable to determine if the duration of follow-up was <60 days or they were lost to follow-up.

Results

Of all patients who met the IgG4 staining criteria (n = 119), half (n = 57) satisfied the IgG4-RD histopathological criteria; 63% were males, age 57.9 ± 14.8 years. The average follow-up was 2.7 ± 2.2 years. The pancreas was the most affected organ in our cohort (26.4%). Almost half of the patients (45.6%; n = 26) were managed surgically, 21.1% (n = 12) medically, and 24.6% (n = 14) received both types of treatment. Medical treatment included prednisone (45.6%), MTX (5.3%), AZA (7%) and rituximab (8.8%). Remission was achieved by 77% of patients receiving surgical, 67% receiving medical and 72% receiving both treatments.

Conclusion

A histological diagnosis of IgG4-RD could be made in half of the patients who had IgG4⁺ plasma cells ≥10/high-power field or IgG4⁺/IgG⁺ ratio >40%. In our cohort, surgical treatment compared with medical treatment had a higher proportion of remission according to our outcome classification.

Clinical Characteristics of 76 Patients with IgG4-Related Hypophysitis: A Systematic Literature Review

BACKGROUND

IgG4-related hypophysitis (IgG4-RH) is a rare disease, and its prevalence remains unclear. In recent years, an increasing number of cases have been reported because of the increasing recognition of this disease. We aimed to summarize case reports of IgG4-RH and outline the clinical features and outcomes.

METHODS

We performed PubMed search of articles using the search terms "hypophysitis [AND] IgG4." Consequently, only 54 English articles (76 cases) met Leporati's diagnostic criteria.

RESULTS

Of the 76 cases, the ratio of men to women was 1.5 : 1, and the age at diagnosis was 54.1 ± 17.8 years. The median IgG4 concentration was 405.0 mg/dl. Anterior hypopituitarism, isolated central diabetes insipidus, and panhypopituitarism were observed in 14 (18.4%), 12 (15.8%), and 44 (57.9%) cases, respectively. The sequence of anterior hormone deficiency was as follows: gonadotropin (68.4%), ACTH (63.2%), TSH (59.2%), GH (48.7%), and prolactin (42.1%). The median number of involved organs was 1.5, and the lung (18.4%), retroperitoneum (17.1%), kidney (15.8%), submandibular glands (14.5%), and pancreas (13.2%) were the common involved organs. Elevated IgG4 concentration and normal IgG4 level were in 42 (76.4%) and 13 (23.6%) cases, respectively. Patients with elevated serum IgG4 concentration were older (60.9 ± 14.3 vs 45.6 ± 17.4, p=0.001) and male-prone (78.6% vs 40.4%, p=0.003) and had a susceptibility of multiple organ involvement (78.6% vs 35.0%, p=0.001) compared to those with normal serum IgG4 levels. Males were older at disease onset (61.5 ± 12.6 vs 42.9 ± 18.8, p < 0.001) and had a higher IgG4 concentration (425.0 vs 152.5, p=0.029) and a greater number of involved organs (2.0 vs 0.0, p=0.001), while isolated hypophysitis was more prominent in female (63.3% vs 26.1%, p=0.001).

CONCLUSION

In this review, we found that there were different characteristics between different genders. Patients with elevated serum IgG4 level in terms of some clinical features were also different from those with normal serum IgG4 level. However, the data in this review were limited by bias and confounding. Further clinical studies with larger sample sizes are warranted.

Immunoglobulin G4 (IgG4)-Related Hypophysitis

We report two different cases of IgG4-related hypophysitis. In the first case, a pituitary lesion was accompanied by lymphocytic meningitis possibly mimicking tuberculous meningitis. The second case was unassociated with involvement of other organs. No histologic differences were noted between the two cases indicating that the morphologic features of the hypophysial lesion do not depend on the presence of other lesions. The pathogenesis of IgG4 hypophysitis is not known, and further study is necessary to explore the cause, progression, and influencing factors of this disease.

Overlap of IgG4-related Disease and Multicentric Castleman's Disease in a Patient with Skin Lesions

A 59-year-old man presented with multiple dark red erythemas with induration, anemia, and polyclonal hypergammaglobulinemia. A skin biopsy revealed the infiltration of lymphocytes and plasma cells and he was initially diagnosed with multicentric Castleman's disease (MCD). Glucocorticoid treatment was only partially effective. Four years later, the patient's bilateral lacrimal glands gradually became enlarged and a biopsy revealed dense lymphocyte and plasma cell infiltration with an IgG4+/IgG+ plasma cell ratio of 70%. The patient was diagnosed with IgG4-related disease (RD). Rituximab only had a slight effect. This case demonstrates that overlapping features of IgG4-RD and MCD may present in a single patient, which suggests a shared pathogenesis.

Myocardial ischemia as presenting manifestation of IgG4-related disease: a case-based review

Coronary involvement in IgG4-related disease (IgG4-RD) has been scarcely reported, and myocardial ischemia as its presenting feature is even rarer. Here, we describe an additional case with novel and relevant observations. The patient was a previously healthy, middle-aged woman who presented to the clinic with new-onset typical angina. One tumefactive lesion encasing the left anterior descending artery was found during her workup. The most common underlying malignancies with secondary cardiac involvement were rationally ruled out. Symptoms persisted despite medical treatment, and she was therefore referred to surgery. Tumor excision was successfully performed, and she received coronary bypass grafting. IgG4-related coronary arteritis with pseudotumor formation was subsequently diagnosed following the comprehensive diagnostic criteria. This condition was clinically classified as active and circulating plasmablasts were found to be increased (5480/mL), even when these were determined 38 days after surgery. A PET/CT revealed an additional hypermetabolic lymph node. She was therefore treated with rituximab as induction therapy (two 1000 mg doses, administered 15 days apart). Three months later, her disease remained clinically inactive. Circulating plasmablasts were repeated and these had dropped to 0/mL. We thereafter review the current and pertinent literature on the topic, emphasizing the previous cases with similar presenting features (n = 7). We lastly suggest that IgG4-RD should be part of the differential diagnosis of any patient with tumefactive lesions surrounding the coronary arteries, since it can initially presented as sudden cardiac death.

IgG4 deposits in pure and combined membranous lupus nephritis

The aim of this study is to determine the frequency and prognosis of IgG4 deposits in renal biopsy of patients with membranous lupus nephritis (MLN). This is a retrospective cohort study in which we included patients with class V alone or combined (III/V or IV/V) of lupus nephritis according to the 2004 ISN/RPS. All the patients included must have availability of renal tissue for immunohistochemistry analyses. We excluded other classes of lupus nephritis. The renal tissue was examined by a nephro-pathologist. We included 65 patients with MLN; of these, 24 (37 %) were class V, and the other had proliferative concomitant with membranous patterns. Seven renal specimens had IgG4 deposits (10 %). Patients with IgG4 deposits had higher levels of eosinophils in serum. All of the patients with IgG4 had renal involvement as first manifestations of systemic lupus erythematosus. The rate of renal failure was 42 and 43 % in IgG4 positive and negative, respectively, 28 % of IgG4 required renal replacement therapy. From a histological view, 42 % of IgG4 had evidence of arteriolar vasculitis in renal biopsies. Lupus patients with IgG4 deposits were more likely to have renal involvement as a first manifestation of systemic lupus erythematosus, and they course with a worse prognosis since they required more dialysis. Also, they have more probability of vascular inflammation on the renal biopsy.

Biopsy-proven IgG4-related lung disease

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory disorder that may involve single or multiple organs. Biopsy-proven lung involvement of this disease is occasionally reported, but not well understood.

METHODS

Patients with the diagnosis of biopsy-proven IgG4-related lung disease (IgG4-RLD) from Peking Union Medical College Hospital between January 2011 and July 2015 were retrospectively analyzed. Age, sex, clinical symptoms, laboratory findings, pulmonary function test results, chest CT tests, positron emission tomography (PET) examinations, treatments and prognoses were retrieved from medical records and analyzed.

RESULTS

Seventeen patients were included in this study (mean age: 44.8 ± 15.0 years). Ten patients were diagnosed via surgery, and 7 patients were diagnosed via percutaneous transthoracic core-needle lung biopsy. Extrapulmonary involvement was observed in only one patient. The clinical symptoms included cough, fever, dyspnea, chest pain and hemoptysis. The serum IgG4 concentration was elevated in 7/13 patients (mean: 1955 ± 1968 mg/L). The chest CT findings included mainly nodules and masses with spiculated borders, alveolar consolidations with air bronchograms, and ground glass opacities with or without reticular opacities. PET scans indicated increased standardized uptake values, and 7/8 patients were correctly diagnosed with benign inflammation. Corticosteroids and immunosuppressants were administered to 14/17 patients and effectively alleviated the disease.

CONCLUSIONS

In biopsy-proven IgG4-RLD, a normal serum IgG4 concentration is commonly seen, while extrapulmonary involvement is infrequent. Alveolar consolidation with air bronchograms is an important imaging finding of IgG4-RLD, which has not been emphasized before.

[IgG4-related disease]

IgG4-related disease is a recently described clinicopathological entity showing a wide spectrum of clinical manifestations that share a common pathology. Its most characteristic feature is the formation of inflammatory tumors in different organs, which makes differentiation mainly with neoplastic diseases fundamental. The inflammatory process is typically comprised of IgG4 lymphoplasmacytic cells. The pathophysiological role of the immunoglobulin is not clear. The treatment of choice is corticosteroids. This article aims to summarize the main features of the disease.

Current Concepts in Primary Biliary Cirrhosis and Primary Sclerosing Cholangitis

Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are chronic, cholestatic diseases of the liver with common clinical manifestations. Early diagnosis and treatment of PBC slows progression and decreases the need for transplant. However, one-third of patients will progress regardless of treatment. Bilirubin <1.0 and alkaline phosphatase <2.0 x the upper limit of normal at 1 year after treatment appear to predict 10-year survival. Ursodeoxycholic acid (UDCA) is the recommended treatment for PBC, and recent studies with obeticholic acid showed promising results for UDCA non-responders. Unlike PBC, no therapy has been shown to alter the natural history of PSC. The recommended initial diagnostic test for PSC is magnetic resonance cholangiopancreatography, typically showing bile duct wall thickening, focal bile duct dilatation, and saccular dilatation of the intra- and/or extrahepatic bile ducts. Immunoglobulin 4-associated cholangitis must be excluded when considering the diagnosis of PSC, to allow for proper treatment, and monitoring of disease progression. In addition to the lack of therapy, PSC is a pre-malignant condition and close surveillance is indicated.

[Immunoglobulin G4 (IgG4)-related disease. A review of head and neck manifestations]

Immunoglobulin G4 (IgG4)-related disease (also known as hyper-IgG4 disease) is a recently defined emerging condition with highly heterogeneous clinicopathological features and variable disease manifestations. This disorder is characterized by unifocal or multifocal (multiorgan) involvement by tumefactive plasma cell-rich inflammatory infiltrates associated with prominent fibrosclerosis. This not uncommonly interferes with organ function resulting in diverse clinical symptoms. The autoimmune pancreatitis represents the prototype of this disease; however, to date almost all organs have been reported to be involved in this disorder. In the head and neck area several presentations of this disease may be encountered in salivary glands, lacrimal glands, thyroid gland, lymph nodes, soft tissue of the neck, ear and sinonasal tract. However, IgG4 positive plasma cells are occasionally prominent in non-specific chronic inflammatory conditions of the head and neck and the oral cavity unrelated to autoimmune diseases or systemic disorders, thus representing diagnostic pitfalls. The diagnosis of IgG4-related disease should be based on a combination of typical histological, clinical and serological findings.

Structural determinants of unique properties of human IgG4-Fc

Human IgG4, normally the least abundant of the four subclasses of IgG in serum, displays a number of unique biological properties. It can undergo heavy-chain exchange, also known as Fab-arm exchange, leading to the formation of monovalent but bispecific antibodies, and it interacts poorly with FcγRII and FcγRIII, and complement. These properties render IgG4 relatively “non-inflammatory” and have made it a suitable format for therapeutic monoclonal antibody production. However, IgG4 is also known to undergo Fc-mediated aggregation and has been implicated in auto-immune disease pathology. We report here the high-resolution crystal structures, at 1.9 and 2.35 Å, respectively, of human recombinant and serum-derived IgG4-Fc. These structures reveal conformational variability at the C_H3–C_H3 interface that may promote Fab-arm exchange, and a unique conformation for the FG loop in the C_H2 domain that would explain the poor FcγRII, FcγRIII and C1q binding properties of IgG4 compared with IgG1 and -3. In contrast to other IgG subclasses, this unique conformation folds the FG loop away from the C_H2 domain, precluding any interaction with the lower hinge region, which may further facilitate Fab-arm exchange by destabilisation of the hinge. The crystals of IgG4-Fc also display Fc–Fc packing contacts with very extensive interaction surfaces, involving both a consensus binding site in IgG-Fc at the C_H2–C_H3 interface and known hydrophobic aggregation motifs. These Fc–Fc interactions are compatible with intact IgG4 molecules and may provide a model for the formation of aggregates of IgG4 that can cause disease pathology in the absence of antigen.

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The first high-resolution crystal structures of IgG4-Fc have been solved.

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Arg409 adopts two conformations, each with a different effect on the C_H3–C_H3 interface.

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Crystal packing analysis reveals a novel Fc–Fc interface.

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The C_H2 domain FG loop adopts a unique conformation, affecting FcγR and C1q binding.

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The IgG4-Fc crystal structures explain unique biological properties of IgG4.