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.

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.

Resolution of Spurious Immunonephelometric IgG Subclass Measurement Discrepancies by LC-MS/MS.

BACKGROUND: The Binding Site immunonephelometric (IN) IgG subclass reagents (IgG1, IgG2, IgG3, IgG, BSIN) are used for assessment of both immunodeficiency and IgG4-related disease (IgG4-RD). In our laboratory, suspected analytic errors were noted in patients with increases in IgG4: The sum of the individual IgG subclasses was substantially greater than the measured total IgG concentrations (unlike samples with normal IgG4), and the IgG4 concentration was always less than the IgG2 concentration. METHODS: We developed a tryptic digest LC-MS/MS method to quantify IgG1, IgG2, IgG3, and IgG4 in serum. Samples with IgG4 concentrations ranging from <0.03 g/L to 32 g/L were reanalyzed by LC-MS/MS, and a subset was also reanalyzed by Siemens IN (SIN) subclass measurements. RESULTS: Multivariate linear regression identified 3 subclass tests with multiple predictors of the measured subclass concentration. For these 3 subclasses, the predominant predictors were (in terms of LC-MS/MS IgG subclass measurement coefficients) BSIN IgG1 = 0.89·IgG1 + 0.4·IgG4; BSIN IgG2 = 0.94·IgG4 + 0.89·IgG2; and SIN IgG2 = 0.72·IgG2 + 0.24·IgG4. CONCLUSIONS: There is apparent IgG4 cross-reactivity with select IN subclass measurements affecting tests from both vendors tested. These findings can be explained either by direct cross-reactivity of the IN reagents with the IgG4 subclass or unique physicochemical properties of IgG4 that permit nonspecific binding of IgG4 heavy chain to other IgG immunoglobulin heavy chains. Irrespective of the mechanism, the observed intermethod discrepancies support the use of LC-MS/MS as the preferred method for measurement of IgG subclasses when testing patients with suspected IgG4-RD.

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.

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.

B-cell depletion attenuates serological biomarkers of fibrosis and myofibroblast activation in IgG4-related disease.

OBJECTIVES: Fibrosis is a predominant feature of IgG4-related disease (IgG4-RD). B-cell depletion induces a prompt clinical and immunological response in patients with IgG4-RD, but the effects of this intervention on fibrosis in IgG4-RD are unknown. We used the enhanced liver fibrosis (ELF) score to address the impact of rituximab on fibroblast activation. The ELF score is an algorithm based on serum concentrations of procollagen-III aminoterminal propeptide, tissue inhibitor of matrix metalloproteinase-1 and hyaluronic acid. METHODS: Ten patients with active, untreated IgG4-RD were enrolled. ELF scores were measured and correlated with the IgG4-RD Responder Index, serum IgG4, circulating plasmablasts and imaging studies. Through immunohistochemical stains for CD3, CD20, IgG4 and α-smooth muscle actin, we assessed the extent of the lymphoplasmacytic infiltration and the degree of fibroblast activation in one patient with tissue biopsies before and after rituximab. RESULTS: The ELF score was increased in patients with IgG4-RD compared with healthy controls (8.3±1.4 vs 6.2±0.9; p=0.002) and correlated with the number of organs involved (R(2)=0.41; p=0.04). Rituximab induced significant reductions in the ELF score, the number of circulating plasmablasts and the IgG4-RD Responder Index (p<0.05 for all three parameters). Rituximab reduced both the lymphoplasmacytic infiltrate and myofibroblast activation. IgG4-RD relapse coincided with recurrent increases in the ELF score, indicating reactivation of collagen deposition. CONCLUSIONS: The ELF score may be a clinically useful indicator of active fibrosis and the extent of disease in IgG4-RD. B-cell depletion has the potential to halt continued collagen deposition by attenuating the secretory phenotype of myofibroblasts in IgG4-RD lesions.

Plasmablasts as a biomarker for IgG4-related disease, independent of serum IgG4 concentrations.

OBJECTIVES: We examined the utility of circulating total and IgG4+ plasmablasts as biomarkers of diagnosis and disease activity in IgG4-related disease (IgG4-RD). MATERIALS METHODS: We evaluated patients with active, untreated, biopsy-proven IgG4-RD affecting various organs. Flow cytometry was used to measure total plasmablast and IgG4+ plasmablast counts by gating peripheral blood for CD19lowCD38+CD20-CD27+ cells and CD19lowCD38+CD20-CD27+IgG4+ cells. Serum IgG4 concentrations were measured by nephelometry. We compared 37 IgG4-RD patients to 35 controls, including healthy individuals (n=14) and patients with other inflammatory diseases before treatment (n=21). RESULTS: The IgG4-RD patients' mean age was 59, and 68% were male. Fourteen patients (38%) had three or more organs involved. The IgG4-RD patients had substantially elevated total plasmablast counts (median 4698/mL, range 610-79524/mL) compared to both untreated disease controls (median 592/mL, range 19-4294/mL; p < 0.001) and healthy controls (median 94/mL, range 1-653/mL; p < 0.001). Thirteen IgG4-RD patients (36%) had normal serum IgG4 concentrations (mean 60 mg/dL, range 5-123 mg/dL, normal <135 mg/dL). However, the median plasmablast count was not significantly lower in that subset with normal serum IgG4 concentrations (3784/mL) compared to those with elevated serum IgG4 (5155/mL) (p = 0.242). Among the 12 rituximab (RTX)-treated patients, the median plasmablast level during disease flare was 6356/mL (range 1123-41589/mL), declining to 1419/mL (range 386/mL-4150/mL) during remission (p < 0.01). CONCLUSIONS: Circulating plasmablasts are elevated in active IgG4-RD, even in patients with normal serum IgG4 concentrations. Plasmablast counts are a potentially useful biomarker for diagnosis, assessing response to treatment, and determining the appropriate time for re-treatment.

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.

De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease.

BACKGROUND: IgG4-related disease (IgG4-RD) is a poorly understood, multiorgan, chronic inflammatory disease characterized by tumefactive lesions, storiform fibrosis, obliterative phlebitis, and accumulation of IgG4-expressing plasma cells at disease sites. OBJECTIVE: The role of B cells and IgG4 antibodies in IgG4-RD pathogenesis is not well defined. We evaluated patients with IgG4-RD for activated B cells in both disease lesions and peripheral blood and investigated their role in disease pathogenesis. METHODS: B-cell populations from the peripheral blood of 84 patients with active IgG4-RD were analyzed by using flow cytometry. The repertoire of B-cell populations was analyzed in a subset of patients by using next-generation sequencing. Fourteen of these patients were longitudinally followed for 9 to 15 months after rituximab therapy. RESULTS: Numbers of CD19(+)CD27(+)CD20(-)CD38(hi) plasmablasts, which are largely IgG4(+), are increased in patients with active IgG4-RD. These expanded plasmablasts are oligoclonal and exhibit extensive somatic hypermutation, and their numbers decrease after rituximab-mediated B-cell depletion therapy; this loss correlates with disease remission. A subset of patients relapse after rituximab therapy, and circulating plasmablasts that re-emerge in these subjects are clonally distinct and exhibit enhanced somatic hypermutation. Cloning and expression of immunoglobulin heavy and light chain genes from expanded plasmablasts at the peak of disease reveals that disease-associated IgG4 antibodies are self-reactive. CONCLUSIONS: Clonally expanded CD19(+)CD27(+)CD20(-)CD38(hi) plasmablasts are a hallmark of active IgG4-RD. Enhanced somatic mutation in activated B cells and plasmablasts and emergence of distinct plasmablast clones on relapse indicate that the disease pathogenesis is linked to de novo recruitment of naive B cells into T cell-dependent responses by CD4(+) T cells, likely driving a self-reactive disease process.

Prevalence of atopy, eosinophilia, and IgE elevation in IgG4-related disease.

IgG4-related disease (IgG4-RD) is a fibroinflammatory disorder that can affect virtually every organ system. T-helper type 2 responses have been presumed to be pathogenic in this disease, and a high proportion of patients with IgG4-RD are reported to have longstanding allergies, peripheral blood eosinophilia, and serum IgE elevation. It has therefore been proposed that allergic mechanisms drive IgG4-RD. However, no epidemiological assessment of atopy, peripheral blood eosinophilia, and serum IgE concentrations has ever been undertaken in patients with IgG4-RD. In this study, we evaluated these parameters in a large cohort of patients with IgG4-RD in whom a wide range of organs were affected by disease. Our results demonstrate that the majority of patients with IgG4-RD are nonatopic. Nevertheless, a subset of nonatopic subjects exhibit peripheral blood eosinophilia and elevated IgE, suggesting that processes inherent to IgG4-RD itself rather than atopy per se contribute to the eosinophilia and IgE elevation observed in the absence of atopy.

IgG4-related disease and other causes of inflammatory meningeal disease.

Immunoglobulin-4 (IgG4-) related disease is a newly described treatable condition that has recently expanded the differential diagnosis of inflammatory meningeal disorders. This review will discuss the main clinical and pathophysiological features of IgG4-related meningeal disease in the context of meningeal inflammatory disorders in general. Particular attention will be dedicated to the differential diagnosis and the different therapeutic approaches.

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.

The latest on IgG4-RD: a rapidly emerging disease.

PURPOSE OF REVIEW: Provide an update of the developments in IgG4 related disease within the last year in terms of nomenclature, diagnostic criteria and clinical features. RECENT FINDINGS: The number of diseases associated with IgG4 related disease continues to grow. The entities of idiopathic orbital inflammation, idiopathic cervical fibrosis, eosinophilic angiocentric fibrosis, reactive nodular fibrous pseudotumor, sclerosing mesenteritis, and membranous glomerulonephritis should all be added to the list of diseases associated with the IgG4 related disease spectrum. The issues of nomenclature and diagnostic criteria for IgG4 related disease have important recent developments as well. SUMMARY: The diagnosis of IgG4 related disease continues to be challenging. Increasing recognition of IgG4 related disease has led to a large body of literature on organ sites of involvement. Understanding how the disease manifests itself is critical to diagnosis and ultimately treatment.