Mass spectrometry in IgG4-related disease diagnosis.

We compared liquid chromatography tandem mass spectrometry (LC-MS/MS) against Binding Site immunonephelometry (BSIN) with regards to these methods' abilities to diagnose IgG4-related disease (IgG4-RD). IgG subclasses were gathered from laboratory from December 2011 to December 2020. The IgG4-RD positive and negative patients were diagnosed according to the ACR/EULAR classification criteria by extensive chart review. Both methods' results were compared in terms of test characteristics. For BSIN, there were 43 IgG4-RD positive cases and 174 disease negative cases, while for LC-MS/MS, there were 102 IgG4-RD positive cases and 562 disease negative cases. The majority of IgG4-RD patients by BSIN and LC-MS/MS had an elevated IgG4 level, 81% and 86%, respectively. For BSIN, the ROC curve, cut-off value of 1.25 g/L, had a sensitivity of 81% and a specificity of 84%. For LC-MS/MS, the ROC curve, cut-off value of 1.25 g/L, had a sensitivity of 86% and a specificity of 84%. The responder index score to IgG4 level r-correlation value for BSIN and LC-MS/MS was 0.5 and 0.6, respectively. In our center, LC-MS/MS and BSIN are equivalent test methods in IgG4-RD diagnosis. IgG4 level does correlate with disease activity by the responder index. LC-MS/MS is a valid and equally reliable alternative to BSIN in the diagnosis of IgG4-related disease.

Hidden IgG4-Related Coronary Disease.

OBJECTIVES: We present a full autopsy with a focused radiology and pathologic review of the coronary arteries. We hope that the results described in this article will help create better diagnostic measures and prevent future coronary artery vasculitis misdiagnosis. METHODS: A full autopsy was performed on the body of Dr Myung Choong Yoon, with full consent from the family, within the department of pathology and laboratory medicine at Vancouver General Hospital. Tissue samples from the heart, brain, lungs, and spinal cord were submitted to specialist pathologists for histologic processing. RESULTS: Cardiac gated computed tomography coronary angiography suggested periarteritis. Coexistent calcified coronary atherosclerosis with linear calcifications was present along the luminal wall, along with coronary artery ectasia. Histologic assessment confirmed features of dense adventitial fibrosis around the coronary arteries, with an exuberant lymphoplasmacytic infiltrate and numerous plasma cells consistent with IgG4-related disease. The media of the coronary arteries was markedly attenuated or completely absent, which likely contributed to the coronary arterial ectasia noted microscopically. These findings confirmed IgG4-related coronary arteritis. CONCLUSIONS: Coronary periarteritis is an uncommon manifestation of IgG4-related disease established radiographically and later by autopsy.

IgG4 plasma cell myeloma without clinical evidence of IgG4-related disease: a report of two cases.

Background: Serum IgG4 is typically measured to investigate for Immunoglobulin G4-related Disease (IgG4-RD), a fibroinflammatory condition associated with polyclonal increase in serum IgG4. However, increased IgG4 can also be monoclonal, and little is known about IgG4 myeloma. Methods: We describe two cases of IgG4 myeloma without clinical, radiologic, or laboratory features of IgG4-related disease. Results: An 84 year old man presented with anemia and compression fractures and a 77 year old man presented with anemia, hypercalcemia and renal failure. Both had markedly elevated monoclonal serum IgG4, 34 g/L and 48 g/L in the beta region, and increased IgG positive bone marrow plasma cells, 50% and 80%, respectively. Neither had clinical or radiological manifestations of IgG4-related disease (IgG4-RD) such as salivary or lacrimal gland swelling, autoimmune pancreatitis , or retroperitoneal fibrosis. Both cases responded well to standard myeloma therapy. The IgG4 paraprotein caused spuriously elevated beta-2 microglobulin of 45.2 mg/L in case two due to interference with the assay. Conclusion: These cases illustrate the importance of performing serum protein electrophoresis in tandem with IgG subclasses to distinguish between polyclonal and monoclonal increases in serum IgG4. The lack of typical IgG4-RD features in these two patients suggests that monoclonal elevation in serum IgG4 alone is insufficient to cause the organ damage characteristic of IgG4-RD. Larger studies of IgG myeloma subtypes are warranted to explore whether IgG1, IgG2, IgG3 and IgG4 myeloma differ in natural history and whether the interference with beta-2 microglobulin is specific to IgG4 monoclonal proteins.

Causes of hypereosinophilia in 100 consecutive patients.

BACKGROUND: Hypereosinophilia (HE, persistent peripheral blood eosinophilia > 1.5 × 109 /L) and hypereosinophilic syndrome (HES, HE with end-organ damage) are classified as primary (due to a myeloid clone), secondary (due to a wide variety of reactive causes), or idiopathic. Diagnostic evaluation of eosinophilia is challenging, in part because secondary causes of HE/HES such as lymphocyte-variant HES (L-HES) and vasculitis are difficult to diagnose, and emerging causes such as immunoglobulin G4-related disease (IgG4-RD) have rarely been examined. OBJECTIVE AND METHODS: We reviewed 100 consecutive patients with HE/HES who underwent extensive evaluation for primary and secondary eosinophilia at a single tertiary care center to determine causes of HE/HES in a modern context. RESULTS: Six patients had primary HE/HES, 80 had a discrete secondary cause identified, and 14 had idiopathic HE/HES. The most common causes of secondary eosinophilia were L-HES/HES of unknown significance (L-HESus) (20), IgG4-RD (9), and eosinophilic granulomatosis with polyangiitis (EGPA) (8). CONCLUSIONS: In contrast to other large published series of HE/HES, most patients in this study were found to have a discrete secondary cause of eosinophilia and only 14 were deemed idiopathic. These findings highlight the importance of extensive evaluation for secondary causes of eosinophilia such as L-HES, IgG4-RD, and EGPA.

Clinical utility of serum IgG4 measurement.

This article will review the structure and function of IgG4, methods of measuring serum IgG4 concentrations, clinical conditions associated with increased and decreased serum IgG4, and the test characteristics of serum IgG4 in the diagnosis and management of Immunoglobulin G4-Related Disease (IgG4-RD). The four subclasses of IgG were discovered in 1964 through experiments on monoclonal IgG in patients with myeloma. Since 2001, interest in measuring serum IgG subclasses has increased dramatically due to the emergence of IgG4-RD, a multisystem fibroinflammatory condition wherein polyclonal serum IgG4 concentration is increased in approximately 70% of cases. Increased serum IgG4 typically manifests as a restriction in the anodal gamma region on serum protein electrophoresis, often with beta-gamma bridging, and can be mistaken as a monoclonal protein or polyclonal increase in IgA. Limitations of current clinical methods used in quantitation of serum IgG4 concentrations will be discussed, including the common immunonephelometric assays and LC-MS/MS based assays. Polyclonal IgG4 elevation is not specific for IgG4-RD, and may also occur in conditions such as eosinophilic granulomatosis with polyangiitis (EGPA), lymphoma, and multicentric Castleman disease (MCD). Race and gender differences also affect interpretation of serum IgG4 concentrations, for instance Asians have a higher serum IgG4 concentration than Whites and males have a higher concentration than females.

IgG4-related disease: what a hematologist needs to know.

IgG4-related disease is a fibro-inflammatory condition that can affect nearly any organ system. Common presentations include major salivary and lacrimal gland enlargement, orbital disease, autoimmune pancreatitis, retroperitoneal fibrosis and tubulointerstitial nephritis. This review focuses on the hematologic manifestations of IgG4-related disease, including lymphadenopathy, eosinophilia, and polyclonal hypergammaglobulinemia. The disease can easily be missed by unsuspecting hematologists, as patients may present with clinical problems that mimic disorders such as multicentric Castleman disease, lymphoma, plasma cell neoplasms and hypereosinophilic syndromes. When IgG4-related disease is suspected, serum protein electrophoresis and IgG subclasses are helpful as initial tests but a firm histological diagnosis is essential both to confirm the diagnosis and to rule out mimickers. The central histopathological features are a dense, polyclonal, lymphoplasmacytic infiltrate enriched with IgG4-positive plasma cells (with an IgG4/IgG ratio >40%), storiform fibrosis, and obliterative phlebitis. Importantly for hematologists, the latter two features are seen in all tissues except bone marrow and lymph nodes, making these two sites suboptimal for histological confirmation. Many patients follow an indolent course and respond well to treatment, but a significant proportion may have highly morbid or fatal complications such as periaortitis, severe retroperitoneal fibrosis or pachymeningitis. Corticosteroids are effective but cause new or worsening diabetes in about 40% of patients. Initial response rates to rituximab are high but durable remissions are rare. More intensive lymphoma chemotherapy regimens may be required in rare cases of severe, refractory disease, and targeted therapy against plasmablasts, IgE and other disease biomarkers warrant further exploration.

A young woman with steroid-responsive, IgG4-positive plasma cell-enriched cystic lymphangioma and chylous ascites.

Lymphangiomas are benign tumors of the lymphatic vessels, which can be inflammatory and occasionally steroid-responsive. IgG4-related disease (IgG4-RD) is a recently defined fibro-inflammatory condition. We describe a novel association between reactive IgG4+ plasma cells and cystic lymphangioma in a young woman who had a dramatic clinical response to steroids.

Utility of Serum IgG4 Levels in a Multiethnic Population.

BACKGROUND: IgG4-related disease (IgG4-RD) is a recently recognized condition defined by characteristic histopathologic findings in affected organs. Serum IgG4 concentration is often but not always elevated. The sensitivity and specificity of serum IgG4 vary greatly across studies and has been anecdotally associated to ethnicity. Our study was conducted to investigate the difference in serum IgG4 levels between Asian and non-Asian patients with IgG4-RD. METHODS: This is a single-center retrospective study of 26 Asian and 10 non-Asian patients with histologically confirmed IgG4-RD. Serum IgG4 levels, clinical features and other laboratory findings were compared between the 2 groups, 31 Asian and 11 non-Asian patients with non-IgG4-RD rheumatic diseases were randomly identified to evaluate test characteristics of serum IgG4 measurement. RESULTS: Median serum IgG4 at time of diagnosis was significantly higher in Asian (median = 11.2g/L, interquartile range: 4.6-19.7) than non-Asian patients (median = 2.9g/L, interquartile range: 0.7-5.4, P = 0.0094), as well as the median serum IgG and total protein. Asian patients had more eosinophilia and polyclonal hypergammaglobulinemia than non-Asian patients (P = 0.016 and 0.001, respectively). Test sensitivity was higher in Asian (96%) than non-Asian patients (67%), whereas test specificity was higher in non-Asian patients (91% versus 71%). CONCLUSION: Asian patients with IgG4-RD have more exuberant serum IgG4, IgG and polyclonal hypergammaglobulinemia than non-Asian patients; the mechanism of this difference requires further study. These findings have significant clinical importance and must be accounted for in the diagnostic workup of patients in multiethnic settings.

IgG4-related disease and lymphocyte-variant hypereosinophilic syndrome: A comparative case series.

OBJECTIVE: To compare the clinical and laboratory features of IgG4-related disease (IgG4-RD) and lymphocyte-variant hypereosinophilic syndrome (L-HES), two rare diseases that often present with lymphadenopathy, gastrointestinal symptoms, eosinophilia, and elevated immunoglobulins/IgE. METHOD: Comparative case series of 31 patients with IgG4-RD and 13 patients with L-HES. RESULTS: Peripheral blood eosinophilia was present in eight of 31 patients with IgG4-RD compared to 13 of 13 patients with L-HES (median eosinophils 0.4 vs 7.0 giga/L, P=.001) and 12 of 20 patients with IgG4-RD had increased serum IgE compared to eight of 13 patients with L-HES, P=.930. Twenty-seven of 30 patients with IgG4-RD had elevated serum IgG4 compared to five of 12 patients with L-HES (median IgG4 9.6 g/L vs 0.80 g/L, P=.002). Flow cytometry demonstrated an aberrant T-cell phenotype in 7 of 23 patients with IgG4-RD and 13 of 13 patients with L-HES (P<.001). T-cell clonality by PCR was positive in 12 of 23 patients with IgG4-RD vs 10 of 13 patients with L-HES (P=.143). Patients in both groups received corticosteroids as first-line therapy. For refractory disease in IgG4-RD, rituximab was the most common steroid-sparing agent, whereas in L-HES, it was pegylated interferon-α-2a. CONCLUSION: The overlapping features of these two diseases with divergent treatment options demonstrate the importance of familiarity with both entities to optimize diagnosis and treatment.

Clonal expansion of CD4(+) cytotoxic T lymphocytes in patients with IgG4-related disease.

BACKGROUND: IgG4-related disease (IgG4-RD) is a systemic condition of unknown cause characterized by highly fibrotic lesions with dense lymphoplasmacytic infiltrates. CD4(+) T cells constitute the major inflammatory cell population in IgG4-RD lesions. OBJECTIVE: We used an unbiased approach to characterize CD4(+) T-cell subsets in patients with IgG4-RD based on their clonal expansion and ability to infiltrate affected tissue sites. METHODS: We used flow cytometry to identify CD4(+) effector/memory T cells in a cohort of 101 patients with IgG4-RD. These expanded cells were characterized by means of gene expression analysis and flow cytometry. Next-generation sequencing of the T-cell receptor ß chain gene was performed on CD4(+)SLAMF7(+) cytotoxic T lymphocytes (CTLs) and CD4(+)GATA3(+) TH2 cells in a subset of patients to identify their clonality. Tissue infiltration by specific T cells was examined by using quantitative multicolor imaging. RESULTS: CD4(+) effector/memory T cells with a cytolytic phenotype were expanded in patients with IgG4-RD. Next-generation sequencing revealed prominent clonal expansions of these CD4(+) CTLs but not CD4(+)GATA3(+) memory TH2 cells in patients with IgG4-RD. The dominant T cells infiltrating a range of inflamed IgG4-RD tissue sites were clonally expanded CD4(+) CTLs that expressed SLAMF7, granzyme A, IL-1ß, and TGF-ß1. Clinical remission induced by rituximab-mediated B-cell depletion was associated with a reduction in numbers of disease-associated CD4(+) CTLs. CONCLUSIONS: IgG4-RD is prominently linked to clonally expanded IL-1ß- and TGF-ß1-secreting CD4(+) CTLs in both peripheral blood and inflammatory tissue lesions. These active, terminally differentiated, cytokine-secreting effector CD4(+) T cells are now linked to a human disease characterized by chronic inflammation and fibrosis.

Rituximab for IgG4-related disease: a prospective, open-label trial.

OBJECTIVES: To evaluate the efficacy of rituximab (RTX) in IgG4-related disease (IgG4-RD) in an open-label pilot trial. METHODS: We treated 30 IgG4-RD patients with two doses of RTX (1000 mg each). The participants were either treated with RTX alone (n = 26; 87%) or required to discontinue baseline glucocorticoids (GC) within 2 months (n = 4; 13%). Disease activity was measured by the IgG4-RD Responder Index (IgG4-RD RI) and physician's global assessment (PGA). Disease response was defined as the improvement of the IgG4-RD RI by two points. The primary outcome, measured at 6 months, was defined as: (1) decline of the IgG4-RD RI ≥2 points compared with baseline; (2) no disease flares before month 6; and (3) no GC use between months 2 and 6. Complete remission was defined as an IgG4-RD RI score of 0 with no GC use. RESULTS: Disease responses occurred in 97% of participants. The baseline IgG4-RD RI and PGA values, 11±7 and 63±22 mm, respectively, declined to 1±2 and 11±16 mm at 6 months (both p<0.00001). The primary outcome was achieved by 23 participants (77%). Fourteen (47%) were in complete remission at 6 months, and 12 (40%) remained in complete remission at 12  months. Among the 19 with elevated baseline serum IgG4, IgG4 concentrations declined from a mean of 911 mg/dL (range 138-4780 mg/dL) to 422 mg/dL (range 56-2410 mg/dL) at month 6 (p<0.05). However, only 8 (42%) of the 19 achieved normal values. CONCLUSIONS: RTX appears to be an effective treatment for IgG4-RD, even without concomitant GC therapy. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier: NCT01584388.

The diagnostic utility of serum IgG4 concentrations in IgG4-related disease.

OBJECTIVES: We evaluated the sensitivity, specificity and positive and negative predictive values of elevated serum IgG4 concentrations for the diagnosis of IgG4-RD. METHODS: Between 2001 and 2011, 190 unique patients had elevated serum IgG4 measurements. We reviewed electronic medical records to determine the indication for IgG4 measurement and underlying clinical diagnosis. Additionally, we reviewed the records of 190 other randomly selected patients from a pool of 3360 with normal results, to evaluate test characteristics of the IgG4 measurement. RESULTS: Among 380 patients analysed, 72 had either probable or definite IgG4-RD. Sixty-five of the 72 IgG4-RD patients had elevated serum IgG4 concentrations (mean: 405 mg/dL; range 140-2000 mg/dL), for a sensitivity of 90%. Among the 308 subjects without IgG4-RD, 125 had elevated IgG4 (mean: 234 mg/dL; range 135-1180 mg/dL) and 183 had normal IgG4 concentrations, for a specificity of 60%. The negative predictive value of a serum IgG4 assay was 96%, but the positive predictive value only 34%. Analysis of the serum IgG4/total IgG ratio did not improve these test characteristics. Doubling the cutoff for IgG4 improved specificity (91%) but decreased sensitivity to 35%. DISCUSSION: Multiple non-IgG4-RD conditions are associated with elevated serum IgG4, leading to poor specificity and low positive predictive value for this test. A substantial subset of patients with biopsy-proven IgG4-RD do not have elevated serum IgG4. Neither doubling the cutoff for serum IgG4 nor examining the serum IgG4/IgG ratio improves the overall test characteristics for the diagnosis of IgG4-RD.

Brief Report: spuriously low serum IgG4 concentrations caused by the prozone phenomenon in patients with IgG4-related disease.

OBJECTIVE: To determine the frequency of the prozone effect in patients with IgG4-related disease (IgG4-RD). METHODS: After identifying the prozone effect in an index patient with IgG4-RD, we examined additional samples to determine the frequency of this phenomenon. Thirty-eight serum samples obtained from patients with IgG4-RD whose results had been reported previously were retested. The serum IgG4 concentrations determined by this repeat analysis were compared with the originally reported values. RESULTS: In 10 (26%) of 38 patients, the originally reported IgG4 values were falsely low; the prozone effect was identified in each of these 10 samples. Correction of the prozone effect by sample dilution led to revision of the mean serum IgG4 concentration in the 10 samples, from 26 mg/dl to 2,008 mg/dl (normal range 2.4-121 mg/dl). All 10 patients whose samples were affected by the prozone effect had active IgG4-RD. Failure to detect the elevated serum IgG4 concentrations had a direct impact on the decision not to institute treatment in these patients. CONCLUSION: The prozone effect may lead to major underestimations of IgG4 concentrations in patients with IgG4-RD and offers a potential explanation for the poor correlation observed between disease activity and serum IgG4 levels in some patients. This phenomenon should be considered if the serum IgG4 measurement appears discordant with the clinicopathologic diagnosis and the clinical assessment of disease activity.

IgG4-related disease and hypertrophic pachymeningitis.

Hypertrophic pachymeningitis (HP) is an inflammatory condition in which the dura mater of the cranium or spine becomes thickened, leading to symptoms that result from mass effect, nerve compression, or vascular compromise. The differential diagnosis of HP includes immune-mediated conditions such as rheumatoid arthritis and vasculitis, malignancies, and infections. Many times, no diagnosis is reached; in such cases, the disease has been described as idiopathic HP. IgG4-related disease (IgG4-RD) is a recently described inflammatory condition known to cause tumefactive lesions at myriad anatomical locations. Both IgG4-RD and idiopathic HP share similar demographics, histopathology, and natural history. We hypothesized that IgG4-RD is a common cause of idiopathic HP.To investigate this hypothesis, we identified all pathology specimens diagnosed as noninfectious HP during 25 years at our institution. Fourteen cases had stained slides and paraffin blocks to permit review of the original hematoxylin and eosin stained slides as well as immunostaining of cell blocks. Recently published consensus guidelines describing characteristic histopathology and the necessary quantity of IgG4+ plasma cell infiltrate were used to diagnose IgG4-RD.Four cases (66.6%) that had been regarded previously as representing idiopathic HP were diagnosed as IgG4-RD; of all the reviewed cases, IgG4-RD represented 29% of cases. Of the remaining cases, 3 cases were associated with granulomatosis with polyangiitis (GPA), 2 with lymphoma, and 1 each with rheumatoid arthritis, giant cell arteritis, and sarcoidosis. Two of the cases could not be diagnosed more precisely and were classified as undifferentiated HP. Clinical history, serologic tests, cerebrospinal fluid studies, and radiology alone could not identify the cause of HP. Rather, biopsy with histopathology and immunostaining was necessary to reach an accurate diagnosis. Significant IgG4+ plasma cell infiltrates were observed in rheumatoid arthritis, granulomatosis with polyangiitis, and lymphoma, underscoring the importance of histopathology in making the diagnosis of IgG4-RD.This case series demonstrates that IgG4-RD may be the most common etiology of noninfectious HP and highlights the necessity of biopsy for accurate diagnosis.