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Background: Hypereosinophilic syndromes (HES) are defined as hypereosinophilia with eosinophil-related clinical manifestations, some of which overlap in presentation with asthma, atopic dermatitis, eosinophilic esophagitis, and/or chronic rhinosinusitis with nasal polyps. Dupilumab is approved to treat these conditions but can induce a transient rise in the absolute eosinophil count and rare eosinophil-related complications., Objective: To determine whether eosinophil-related complications of dupilumab are increased in HES., Methods: Retrospective chart review of patients with HES treated with dupilumab enrolled on an institutional review board-approved research protocol at the National Institutes of Health (NCT00001406) or receiving care at Walter Reed National Military Medical Center. Clinical response and treatment-emergent adverse events were recorded. Serum mediators were assessed in a subset of patients before and after dupilumab using stored samples., Results: Among the 28 patients (15 male, 13 female; median age 41.5 y), the most common prescribing indication for dupilumab was chronic rhinosinusitis with nasal polyps (n = 11). Twenty-three patients (82%) showed significant clinical improvement on dupilumab. Hypereosinophilia (absolute eosinophil count > 1.5 × 10 9 /L) recurred or worsened in 9 of 20 patients on dupilumab monotherapy. Moreover, 4 of 20 (20%) patients developed an eosinophil-related complication with dupilumab discontinuation and/or addition of eosinophil-lowering therapy. None of the 8 patients who received dupilumab while in hematological remission on an eosinophil-lowering biologic developed hypereosinophilia or an eosinophil-related complication. Serum immunoglobulin E and eotaxin levels decreased on dupilumab therapy., Conclusions: These data suggest that dupilumab is effective in treating residual symptoms in HES patients but that the incidence of eosinophil-related complications is increased. Concomitant eosinophil-lowering therapy may reduce the risk of eosinophil-related complications during dupilumab therapy in patients with HES., (Published by Elsevier Inc.)

Summary: Eosinophil-associated diseases (EADs) refer to heterogeneous conditions in which eosinophils are believed to play critical pathological roles. They encompass common respiratory conditions, such as asthma, chronic rhinosinusitis with nasal polyps (CRSwNP), less common primary eosinophilic disorders of gastrointestinal tract, and rare conditions including eosinophilic granulomatosis with polyangiitis (EGPA) and hypereosinophilic syndrome (HES). A literature search was carried out in January 2024 in the MEDLINE and Scopus databases using the PubMed search engine (PubMed, National Library of Medicine, Bethesda, MD). We focused on blood eosinophilia and hypereosinophilia. A diagnostic workup is proposed. From allergist's point of view, we focused the review on 4 groups of eosinophilic disorders of specific interest. Our increased understanding of type 2 inflammation and biology has recently led to development of highly effective precision targeted therapies that are now approved for a growing number of eosinophilic disorders. Novel targeted biologics have a major impact on treatment strategies and have resulted in major advances in our understanding of the pathogenesis of these disorders. In the context of EADs, according to the heterogeneity of eosinophilic disorders a multidisciplinary approach should be adopted. Allergists and Clinical Immunologists play an important role as they have a clear understanding of the eosinophilic inflammation and the role of cytokines and are trained to recognize and characterize type 2 (T2) inflammation and its associated pathologies.

Eosinophil sombrero vesicles are large tubular carriers resident in the cytoplasm of human eosinophils, identifiable by transmission electron microscopy, and important for immune mediator transport. Increased formation of sombrero vesicles occurs in activated eosinophils in vitro and in vivo. In tissue sites of eosinophilic cytolytic inflammation, extracellular eosinophil sombrero vesicles are noted, but their frequency and significance in eosinophil-associated diseases remain unclear. Here, we performed comprehensive quantitative transmission electron microscopy analyses and electron tomography to investigate the numbers, density, integrity, and 3-dimensional structure of eosinophil sombrero vesicles in different biopsy tissues from 5 prototypic eosinophil-associated diseases (eosinophilic chronic rhinosinusitis/nasal sinuses, ulcerative colitis/intestines, hypereosinophilic syndrome/skin, dermatitis/skin, and schistosomiasis/rectum). The morphology of extracellular eosinophil sombrero vesicles was also compared with that of cytoplasmic eosinophil sombrero vesicles, isolated by subcellular fractionation from peripheral blood eosinophils. We demonstrated that (i) eosinophil cytolysis, releasing intact sombrero vesicles and membrane-bound granules, is a consistent event in all eosinophil-associated diseases; (ii) eosinophil sombrero vesicles persist intact even after complete disintegration of all cell organelles, except granules (late cytolysis); (iii) the eosinophil sombrero vesicle population, composed of elongated, curved, and typical sombreros, and the eosinophil sombrero vesicle 3-dimensional architecture, diameter, and density remain unchanged in the extracellular matrix; (iv) free eosinophil sombrero vesicles closely associate with extracellular granules; and (v) free eosinophil sombrero vesicles also associate with externalized chromatin during eosinophil ETosis. Remarkably, eosinophil sombrero vesicles appeared on the surface of other cells, such as plasma cells. Thus, eosinophil cytolysis/ETosis can secrete intact sombrero vesicles, alongside granules, in inflamed tissues of eosinophil-associated diseases, potentially serving as propagators of eosinophil immune responses after cell death., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Leukocyte Biology.)

Hypereosinophilic syndrome (HES) encompasses a heterogeneous and complex group of different subtypes within the wider group of hypereosinophilic disorders. Despite increasing research interest, several unmet needs in terms of disease identification, pathobiology, phenotyping, and personalized treatment remain to be addressed. Also, the prospective burden of non-malignant HES and, more in general, HE disorders is currently unknown. On a practical note, shortening the diagnostic delay and the time to an appropriate treatment approach probably represents the most urgent issue, even in light of the great impact of HES on the quality of life of affected patients. The present document represents the first action that the Italian Society of Allergy, Asthma, and Clinical Immunology (SIAAIC) has finalized within a wider project aiming to establish a collaborative national network on HES (InHES-Italian Network on HES) for patients and physicians. The first step of the project could not but focus on defining a common language as well as sharing with all of the medical community an update on the most recent advances in the field. In fact, the existing literature has been carefully reviewed in order to critically integrate the different views on the topic and derive practical recommendations on disease identification and treatment approaches.

Chronic eosinophilic leukemia-not otherwise specified (CEL-NOS) is a rare, aggressive, fatal disease characterized by blood eosinophilia and dysfunction of organs infiltrated with eosinophils. Clinically, the disease manifests with weight loss, cough, weakness, diarrhea, and multi-organ dysfunction that is unresponsive to therapy. We developed a one-time gene therapy for CEL-NOS using an adeno-associated virus (AAV) expressing an anti-eosinophil monoclonal antibody (AAVrh.10mAnti-Eos) to provide sustained suppression of eosinophil numbers in blood, thus reducing eosinophil tissue invasion and organ dysfunction. A novel CEL-NOS model was developed in NOD-scid IL2rγ null (NSG) mice by administration of AAV expressing the cytokine IL5 (AAVrh.10mIL5), resulting in marked peripheral and tissue eosinophilia of the heart, lung, liver, and spleen, and eventually death. Mice were administered AAVrh.10mAnti-Eos (10 11 genome copies) 4 wk after administration of AAVrh.10mIL5 and evaluated for anti-eosinophil antibody expression, blood eosinophil counts, organ eosinophil invasion, and survival. AAVrh.10mAnti-Eos expressed persistent levels of the anti-eosinophil antibody for >24 wk. Strikingly, CEL-NOS treated mice had markedly lower blood eosinophil levels and reduced mortality when compared with control treated mice. These results suggest that a single treatment with AAVrh.10mAnti-Eos has the potential to provide substantial therapeutic benefit to patients with CEL-NOS, a fatal malignant disorder., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Lymphocyte-variant hypereosinophilic syndrome (L-HES) is a rare disease driven by immunophenotypically aberrant T cells producing eosinophilopoetic cytokines such as interleukin-5 (IL-5). Treatment is challenging because L-HES is relatively steroid resistant and not amenable to tyrosine kinase inhibitors. We searched the literature for clinical trials and observational studies, including case reports, of patients treated for L-HES. In all, 25 studies were selected; two were randomised controlled trials of IL-5 blockade, which included some patients with L-HES, and the rest were observational studies. Corticosteroids are often used as first-line therapy, but patients with L-HES have lower response rates than other types of HES. Treatments that reduce symptoms and steroid dependence in some patients include interferon-alpha (IFN-α), anti-IL-5 monoclonal antibodies, cyclosporine and mycophenolate. These drugs target T-cell activation and proliferation, or IL-5 directly. Although effective, IFN-α and cyclosporine were commonly reported to cause side-effects resulting in discontinuation. Alemtuzumab can induce remissions, but these are generally short lived. The anti-IL-5 monoclonal antibodies mepolizumab and benralizumab are effective and well tolerated, but with a high rate of relapse once withdrawn. Hydroxyurea, methotrexate, imatinib were unsuccessful in most patients studied. More prospective clinical trials are needed for patients with L-HES., (© 2021 British Society for Haematology and John Wiley & Sons Ltd.)

Diffuse alveolar hemorrhage (DAH) is a severe and potentially life-threatening disease manifestation. In addition to autoimmune diseases such as antineutrophil cytoplasmic antibody-associated vasculitis and anti-glomerular basement membrane syndrome, pulmonary viral infections are known to be culprits of DAH. Health-care providers worldwide in the coronavirus disease 2019 pandemic have been confronted with an unprecedented number of viral lung infections, with great variance in symptoms and severity. Hemoptysis, the key symptom of DAH, is a rare complication. We present two cases of immunocompromised patients with rapidly developing hypoxemic respiratory failure and evidence of DAH in the context of severe acute respiratory syndrome coronavirus 2 infection., (Copyright © 2020. Published by Elsevier Inc.)

Background: Lymphocytic variant hypereosinophilic syndrome is characterized by marked over-production of eosinophilopoietic factor(s) by dysregulated T cells leading to eosinophil expansion. In most cases, these T cells are clonal and express a CD3 - CD4 + phenotype. As this is a rare disorder, presenting manifestations, disease course, treatment responses, and outcome are not well-characterized. Materials and Methods: In this retrospective single-center observational study, we reviewed medical files of all patients with persistent hypereosinophilia seen between 1994 and 2019 in whom CD3 - CD4 + T cells were detected. Data collection included clinical and biological findings at presentation, treatment responses, disease course, and serial CD3 - CD4 + T cell counts. Results: Our cohort comprises 26 patients, including 2 with hypereosinophilia of undetermined significance. All 24 symptomatic patients had cutaneous lesions and/or angioedema, and fasciitis was present in several cases. The aberrant T cell subset represented 2% or less total lymphocytes in 11 subjects. TCR gene rearrangement patterns on whole blood were polyclonal in these cases, while they all had serum CCL17/TARC levels above 1,500 pg/ml. Disease manifestations were mild and did not require maintenance therapy in roughly one third of the cohort, while two thirds required long-term oral corticosteroids and/or second-line agents. Among these, interferon-alpha was the most effective treatment option with a response observed in 8/8 patients, one of whom was cured of disease. Treatment had to be interrupted in most cases however due to poor tolerance and/or development of secondary resistance. Anti-interleukin-5 antibodies reduced blood eosinophilia in 5/5 patients, but clinical responses were disappointing. A sub-group of 5 patients had severe treatment-refractory disease, and experienced significant disease- and treatment-related morbidity and mortality, including progression to T cell lymphoma in three. Conclusions: This retrospective longitudinal analysis of the largest monocentric cohort of CD3 - CD4 + T cell associated lymphocytic variant hypereosinophilic syndrome published so far provides clinicians confronted with this rare disorder with relevant new data on patient presentation and outcome that should help tailor therapy and follow-up to different levels of disease severity. It highlights the need for novel therapeutic options, especially for the subset of patients with severe treatment-refractory disease. Future research efforts should be made toward understanding CD3 - CD4 + T cell biology in order to develop new treatments that target primary pathogenic mechanisms., (Copyright © 2020 Carpentier, Verbanck, Schandené, Heimann, Trépant, Cogan and Roufosse.)

Purpose of Review: Clinical conditions associated with hypereosinophilia represent a field of particular interest, taking into account the epidemiological impact of the different primary and secondary forms. In addition to a classical Th1 response, also Th2 cells can be involved in the pathogenesis of autoimmune diseases, among them eosinophilic forms such as eosinophilic granulomatosis with polyangiitis., Recent Findings: In patients with severe asthma, recent evidence highlights the role of pathogenic autoantibodies against autologous eosinophil proteins (e.g. eosinophil peroxidase) suggest the role of autoimmune mechanisms, particularly in patients in which asthma is included in eosinophilic vasculitis with antineutrophilic autoantibody positivity. Is now evident that in addition to Th2 cells, also type 2 innate lymphoid cells and Th1/Th17 cells play a central role in the pathogenesis of hypereosinophilic syndrome., Summary: The definition of cellular and molecular mechanisms and the critical role of specific cytokines involved in the pathogenesis of hypereosinophilic syndrome open the way to new therapeutic strategies by using biological agents targeting these specific factors.

A 53-year-old male presented with cough, skin rash and lymphadenopathies complicated with hypereosinophilia (HE) in the blood, and patchy shadows in both lungs on chest computed tomography. Reactive causes for HE were excluded, and no clinical or laboratory features of myeloproliferative disorders could be found. HE caused by aberrant T-cell subsets was suspected because of serum hyper-immunoglobulin E level, and organ involvement of skin and lungs, though we could show neither aberrant T-cell surface markers nor T-cell receptor gene rearrangement. In the course of steroid monotherapy, tolerable maintenance dose could not be attained and the steroid-sparing agents of hydroxycarbamide, cyclosporine and interferon-α were introduced. However, the therapeutic response was inadequate, and organ involvement of lungs and intestinal tract developed. HE caused by aberrant T-cell subsets has steroid resistance and a risk of malignant transition, and we considered this progressive steroid refractoriness to be a sign of such a transition. Cytotoxic chemotherapy or bone marrow transplantation will likely be the next treatment modality in this patient.

Eosinophils and their secretory mediators play an important role in the pathogenesis of infectious and inflammatory disorders. Although eosinophils are largely evolutionally conserved, their physiologic functions are not well understood. Given the availability of new eosinophil-targeted depletion therapies, there has been a renewed interest in understanding eosinophil biology as these strategies may result in secondary disorders when applied over long periods of time. Recent data suggest that eosinophils are not only involved in immunological effector functions but also carry out tissue protective and immunoregulatory functions that actively contribute to the maintenance of homeostasis. Prolonged eosinophil depletion may therefore result in the development of secondary disorders. Here, we review recent literature pointing to important roles for eosinophils in promoting immune defense, antibody production, activation of adipose tissue, and tissue remodeling and fibrosis. We also reflect on patient data from clinical trials that feature anti-eosinophil therapeutics., (© 2019 S. Karger AG, Basel.)

A 46-year-old woman consulted our hospital with diffuse alopecia and blood eosinophilia. Histological examination of the scalp revealed dense eosinophilic infiltration around the hair follicles and in the surrounding subcutis. Oral corticosteroid was effective to reduce hair loss and blood eosinophilia, but these conditions immediately relapsed after ending treatment. In addition to alopecia, she had diarrhea and colitis showing histological findings of dense eosinophilic infiltrations in the submucosa. We diagnosed hypereosinophilic syndrome based on hypereosinophilia of blood and tissue with clinical symptoms of alopecia and diarrhea. We suppose diffuse alopecia showing massive eosinophilic infiltration around the hair follicle is a rare symptom of hypereosinophilic syndrome., (© 2019 Japanese Dermatological Association.)

Introduction : Hypereosinophilic syndromes are a heterogeneous group of disorders that may be associated with life-threatening organ injury as a result of tissues infiltration by eosinophils. The main goal of therapy is to mitigate eosinophil-mediated organ damage. When possible, therapy should be directed at the underlying etiology. However, even in the absence of any known cause, when organ damage is present, hypereosinophilia must be treated promptly and aggressively to reduce potential morbidity and mortality. Areas covered : Conventional therapies, including corticosteroids, hydroxyurea (hydroxycarbamide) and interferon-alpha, have shown variable efficacy and a non-negligible toxicity emphasizing the need of new therapeutic strategies based on drugs with different mechanisms of action. Expert opinion : Tyrosine kinase inhibitors have a central role among targeted therapies of hypereosinophilic syndromes. Imatinib, initially empirically used based on its activity in chronic myeloid leukemia, achieved preliminary excellent results further confirmed in large series of patients. Third-generation tyrosine kinase inhibitors such as ponatinib, while active in vitro and in vivo in animals, still deserve confirmation in properly designed clinical trials. In addition, clinical investigation on monoclonal antibodies against interleukin-5, interleukin-5Rα, IgE, and CD52 represents a promising area of research.

Background: Glucocorticoids (GC) are considered first-line therapy for most patients with hypereosinophilic syndrome (HES). Although response rates are generally high, many patients require moderate to high doses for control of eosinophilia and symptoms, and up to 15% of patients do not respond at all. Despite this, little is known about the mechanisms of GC resistance in patients with HES., Objective: To explore the aetiology of GC resistance in HES., Methods: Clinical data and samples from 26 patients with HES enrolled on a prospective study of GC responsiveness and 23 patients with HES enrolled on a natural history study of eosinophilia for whom response to GC was known were analysed retrospectively. Expression of GC receptor isoforms was assessed by quantitative RT-PCR in purified eosinophils. Serum cytokine levels were quantified by suspension array assay in multiplex., Results: Despite an impaired eosinophil response to GC after 7 days of treatment, the expected rise in absolute neutrophil count was seen in 7/7 GC-resistant patients, suggesting that GC resistance in HES is not a global phenomenon. Eosinophil mRNA expression of glucocorticoid receptor (GR) isoforms (α, β, and P) was similar between GC-sensitive (n = 20) and GC-resistant (n = 9) patients with HES. Whereas geometric mean serum levels were also comparable between GC-r (n = 11) and GC-s (n = 19) for all cytokines tested, serum IL-5 levels were >100 pg/mL only in GC-r patients., Conclusions and Clinical Relevance: These data suggest that the mechanism of GC resistance in HES is not due to a global phenomenon affecting all lineages, but may be due, at least in some patients, to impairment of eosinophil apoptosis by increased levels of IL-5., (Published 2019. This article is a U.S. Government work and is in the public domain in the USA.)

Hypereosinophilic syndromes. Hypereosinophilic syndromes (HES) is a protean condition defined by chronic blood eosinophilia ≥ 1.5 G/L (> 1 month) leading to eosinophilic-related organ damage. HES subtypes includes neoplastic (clonal) disorders (HESN, that comprises FIP1L1-PDGFRA- related chronic eosinophilic leukemia and myeloproliferative and myelodysplastic syndromes associated with eosinophilia) and reactive HES (HESR, that aggregates all conditions e.g. parasitic infections, adverse drug reactions, inflammatory or neoplastic diseases that lead to the production of Th2-related cytokines and thereby to non-clonal hypereosinophilia). HESR also includes the lymphoid variant of HES (HESL), a chronic clonal indolent T-cell lymphoproliferative disorder in which mature peripheral T cells secrete high amounts of IL-5, leading to the polyclonal expansion of eosinophils. Despite an extensive etiological workup, approximately 50% of HES remain of undetermined cause. HES-related clinical manifestations are highly diverse, but dermatological, respiratory and gastro-intestinal symptoms are the most frequent. The long-term prognosis is driven by cardiac involvement and, for patients with HESN and HESL, by the risk of acute transformation into high-grade hematological malignancies. Treatment of HESN relies on tyrosine kinase inhibitors (e.g. imatinib mesylate), while oral glucocorticoids are the usual the fist-line therapy for HESR (including SHEL). In this setting, second-line treatments include hydroxyurea and Peg-interferon alfa-2a. IL-5-targeted therapies are very promising (except for HESN). Yet, to date, their use is restricted to clinical trials and to a compassionate use program dedicated to severe and refractory patients., Competing Interests: M. Groh déclare des liens ponctuels avec GlaxoSmithKline et AstraZeneca (activité de conseil). G. Lefèvre déclare des liens ponctuels avec AstraZeneca et Sanofi-Genzyme (activités de conseil), GlaxoSmithKline (financement recherche, frais de congrès). F. Ackermann, et N. Étienne déclarent n’avoir aucun lien d’intérêts. J. -E. Kahn déclare des liens ponctuels avec GSK (activités de conseil, frais de congrès) et AstraZeneca (activités de conseil).

Hypereosinophilic syndrome is characterized by sustained and marked eosinophilia leading to tissue damage and organ dysfunction. Morbidity and mortality occur primarily due to cardiac and thromboembolic complications. Understanding the cause and mechanism of disease would aid in the development of targeted therapies with greater efficacy and fewer side effects. We discovered a spontaneous mouse mutant in our colony with a hypereosinophilic phenotype. Mice develop peripheral blood eosinophilia; infiltration of lungs, spleen, and heart by eosinophils; and extensive myocardial damage and remodeling. This ultimately leads to heart failure and premature death. Histopathological assessment of the hearts revealed a robust inflammatory infiltrate composed primarily of eosinophils and B-lymphocytes, associated with myocardial damage and replacement fibrosis, consistent with eosinophilic myocarditis. In many cases, hearts showed dilatation and thinning of the right ventricular wall, suggestive of an inflammatory dilated cardiomyopathy. Most mice showed atrial thrombi, which often filled the chamber. Protein expression analysis revealed overexpression of chemokines and cytokines involved in innate and adaptive immunity including IL-4, eotaxin, and RANTES. Disease could be transferred to wild-type mice by adoptive transfer of splenocytes from affected mice, suggesting a role for the immune system. In summary, the pathologies observed in the mutant lines are reminiscent of those seen in patients with hypereosinophilia, where cardiac-related morbidities, like congestive heart failure and thrombi, are the most common causes of death. As such, our model provides an opportunity to test mechanistic hypotheses and develop targeted therapies. NEW & NOTEWORTHY This article describes a new model of heart disease in hypereosinophilia. The model developed as a spontaneous mouse mutant in the colony and is characterized by peripheral blood eosinophilia and infiltration of lungs, spleen, and heart by eosinophils. In the heart, there is extensive myocardial damage, remodeling, fibrosis, and thrombosis, leading to heart failure and death. The immune microenvironment is one of increased innate and adaptive immunity, including Th1 and Th2 cytokines/chemokines. Finally, adoptive transfer of splenocytes transfers disease to recipient mice. In summary, this model provides an opportunity to test mechanistic hypotheses and develop targeted therapies for this rare but devastating disease.

Hypereosinophilic syndrome (HES) is often associated with cutaneous manifestations, mostly pruritic lesions, urticaria and angioedema. Mucosal lesions are rarely seen in HES but, when present, are usually the first manifestation of the disease. The clinical presentation may be heterogeneous, including erosions, aphthae or ulcers, and can be easily confused with other mucocutaneous disorders. Here, we present the case of a 64-year-old man with severe chronic erosive oral mucositis simulating pemphigus in which the finding of persistent eosinophilia and elevation of B 12 vitamin serum levels raised the suspicion of HES. The FIP1L1-PDGFRA fusion gene (4q12) was detected by fluorescence in situ hybridization and the patient was treated with imatinib mesylate with complete response of the disease., (© 2019 Japanese Dermatological Association.)

Hypereosinophilic syndromes (HESs) are a heterogeneous group of rare disorders characterized by peripheral eosinophilia and eosinophilic end organ complications. Conventional therapies, including glucocorticoids and cytotoxic and immunomodulatory agents, have variable efficacy and significant toxicity. Although the recent development of agents that target eosinophils, including tyrosine kinase inhibitors and monoclonal antibodies, provides the possibility of more effective, less toxic approaches to treatment of HES, there are little available data to guide their use in these conditions. In the following review, the controversies regarding the definition and classification of HES will be discussed, and a pragmatic approach to treatment based on clinically defined HES variants will be presented. An illustrative case will be used to highlight the complexities of treatment selection in HES patients., Competing Interests: Conflict-of-interest disclosure: The author declares no competing financial interest., (© 2018 by The American Society of Hematology. All rights reserved.)

Hypereosinophilia (HE) is currently defined by a peripheral blood absolute eosinophil count (AEC) of ≥1,500 cells/microL. Although mild blood eosinophilia (AEC 500-1,500 cells/microL) is observed relatively frequently within the pediatric population, persistent HE is uncommon and should prompt additional clinical evaluation. While the clinical manifestations and underlying etiologies of HE in adults have been well-characterized, there is a paucity of data on HE in children. Limited evidence suggests that many similarities between adult and pediatric HE likely exist, but some important differences remain between these populations. The evaluation of HE in children can be challenging given the broad differential diagnosis, which includes primary hematologic disorders and secondary eosinophilia in which the increased eosinophil levels are propagated by disease states that promote eosinophil production and survival. On the basis of the underlying etiology, clinical manifestations can range from benign, self-resolving elevations in the AEC to life-threatening disorders with the potential for significant end-organ damage. Given the broad differential diagnosis of HE, it remains essential to systematically approach the evaluation of unexplained HE in children. This review will discuss the differential diagnosis for pediatric HE, highlighting etiologies that are more prevalent within the pediatric population. Additionally, a summary of the epidemiology of pediatric HE will be presented, with focus on some of the differences that exist between pediatric and adult HE. Finally, a directed approach to the diagnostic evaluation of children with HE will be discussed.

Eosinophils are bone marrow-derived cells that infiltrate skin and mucous membrane in a broad spectrum of primary and reactive inflammatory diseases and malignancies. The eosinophil has potent proinflammatory activities, particularly, through the effects of its toxic granule proteins. In addition, eosinophils have prothrombotic and profibrotic activities. Eosinophil participation in the pathogenesis of certain diseases without identifiable intact eosinophil infiltration may not be recognized because eosinophil degranulation is poorly visualized on hematoxylin-and-eosin-stained histopathology sections. Eosinophil-related pathophysiology can involve virtually every component of skin. Commonly recognized dermatoses associated with eosinophils are arthropod bite and sting reactions and drug eruptions, "bugs and drugs." Skin involvement is common in eosinophil-related systemic diseases including the hypereosinophilic syndromes. Eosinophil-related pathophysiology may play a key role in numerous disorders that, therefore, may benefit from therapies targeted to reduce or eliminate eosinophils., (Copyright © 2018 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Gleich's syndrome (GS) is characterized by recurrent episodes of angioedema, increase in body weight, fever, hypereosinophilia, and elevated serum IgM. The exact etiology remains unclear. Currently, the only treatment strategy is the administration of high dose of steroids during the acute phases. We report the case of a 37-year-old man suffering from GS with recurrent episodes of angioedema, fever, hypereosinophilia [6,000/mm 3 (45%)], and high eosinophil cationic protein (ECP) (>200 μg/l), treated with oral steroids during the acute phase (prednisone 50-75 mg/day), the dose of maintenance being 25 mg/day. No monoclonal components were identified, and genetic tests exclude mutations including Bcr/Abl, JAK2 V617F, c-KIT D816V, and FIP1L1-PDGFRA. Using Luminex technology, we observed higher serum levels of interleukin (IL)-5, CCL2, and CCL11 during the acute exacerbations in comparison with the clinical remission phases though CCL11 did not achieve statistical significance. The flow-cytometric analysis identified a CD3+ CD8- lymphocyte population with high frequency of IL-4-, IL-5-, and IL-13-producing cells. No clinical benefit was observed after therapeutic strategies with imatinib, interferon-α, cyclosporine-A, and azathioprine. Due to high IL-5 serum levels, an intravenous treatment with anti-IL-5 monoclonal antibody mepolizumab (750 mg every 4 weeks) was started. A reduction in the rate of exacerbation phases/year (10 ± 3 vs 2 ± 1; p  < 0.005), in the eosinophils count both in percentage (28.8 ± 12.8 vs 9.8 ± 3.9; p  < 0.001) and absolute value (2,737 ± 1,946 vs 782 ± 333; p  < 0.001) were observed as well as the ECP serum levels (132.7 ± 62.7 vs 21 ± 14.2 μg/l; p  < 0.05). The daily dose of prednisone was significantly reduced (25 vs 7.5 mg). Any adverse effects were recorded. To the best of our knowledge, this case is the first report of the disease successfully treated with mepolizumab, and it could represent a novel therapeutic strategy in GS.

We, herein, report a 23-year-old male with a rare inherited immunodeficiency disease, hyperimmunoglobulin IgE syndrome (HIES), who developed progressive multifocal leukoencephalopathy (PML) and lymphoma simultaneously. Primary immunodeficiency of the patient has remained undiagnosed until adulthood. PML is a severe demyelinating disease of the central nervous system caused by John Cunningham virus. HIES is a rare, inherited immunodeficiency characterized by high serum levels of IgE, recurrent staphylococcal infection, eczema, and hypereosinophilia. PML may accompany primary immunodeficiency syndromes, but the association with HIES is exceedingly rare. We discuss the imaging findings, medical management, and a review of related literature on primary immunodeficiency cases complicating with PML.

The development and utilization of monoclonal antibodies (mAbs) have been of great interest in all fields of medicine. A substantial increase in the production and development of mAbs has occurred because these biologic agents are proving to be effective and less toxic given their targeted mechanism of action. However, data are limited on coadministration of two or more mAbs. With the increasing availability of mAbs and the comorbidities of some patients, assessment is needed of the ability to safely use multiple mAbs for an individual patient. Although the efficacy of coadministered mAbs may be inferred from their specific targets, we could find no literature reporting such a finding. Herein, we report our experience using two different classes of mAbs to treat hypereosinophilic syndrome and ulcerative colitis in a single patient.

Based on a case report an overview on the differential diagnostic considerations with respect to blood hypereosinophilia (HE) and hypereosinophilic syndromes (HES) in childhood is given. A 13-year-old boy was admitted for the clarification of an asthma. In the blood count an increased HE with 3 500/µl (30%) was found along with elevated total serum IgE and IL-5 level (2 000 IU/ml and 17 pg/ml). Lung function showed an obstruction (FEV1 38%). Radiologically the picture of bronchiectasis and mucus pluggine appeared. In the BAL a HE (76%) with raised IL-5 level was apparent. Histologically asthma was diagnosed with mucostasis, hypertrophy of the bronchial wall musculature and a lung HE. Differential-diagnostically an ABPA, a Churg-Strauss-Syndrome, a parasitosis, drug associated HE, allergies and malignant disease could be excluded. An aberrant T-cell clone in peripheral blood was detected by flow cytometry and T-cell receptor clonal rearrangements by PCR, leading to the diagnosis of a lymphoid variant of HES (L-HES). Failure to detect the FIP1L1-PDGFRA gene fusion and a normal bone marrow examination could exclude a neoplastic HES (HESN). After steroid initiation, prompt decrease of blood eosinophilia with resolution of symptoms was observed. Steroid discontinuation led to eosinophilia recurrence associated with disease symptoms. As steroid-sparing agent the immunosuppressive azathioprine was additionally given; steroid doses could be decreased and stopped in the course. This case demonstrated the range of HE evaluation in infancy. With asthma one should also consider the possibility of a L-HES., (© Georg Thieme Verlag KG Stuttgart · New York.)

Background: Certain hematologic malignancies are associated with hypereosinophilia or tissue eosinophilia. It is unclear if patients with hypereosinophilia are more likely to develop one of these malignancies., Objective: This study sought to quantify the specific hematologic malignancies that developed in patients with preexisting hypereosinophilia., Methods: Adult patients with eosinophilia associated with the development of hematologic malignancy were identified by a retrospective review of the Mayo Clinic patient database between 2000 and 2013., Results: Of 2642 patients identified with eosinophilia, hypereosinophilia, or hypereosinophilic syndrome, 25 (aged 28.8 to 86.1 years; 13 male; 12 female) had a diagnosis of either lymphoma or leukemia. The majority of these patients had non-Hodgkin lymphoma (17 of 25). T-cell-derived lymphomas were more common (12 of 17) than B-cell-derived lymphomas (4 of 17). In patients with leukemia (8 of 25), chronic lymphocytic leukemia (4 of 8) was most common, followed by chronic eosinophilic leukemia (3 of 8). Approximately 5.1% of patients with hypereosinophilia developed a hematologic malignancy. On average, the malignancy developed 30.0 ± 42.7 months after the onset of hypereosinophilia., Conclusions: The development of hematologic malignancies in this referral population with eosinophilia was rare (0.2%), but more common in those with hypereosinophilia (5.1%). Non-Hodgkin's lymphomas, particularly T-cell-derived malignancies, were most commonly diagnosed. Patients with preexisting hypereosinophilia were diagnosed with hematologic conditions that were rarer within the general population., (Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

We report a hitherto undescribed unusual CD30+ clonal T-cell proliferation in a 46-year-old man with the lymphocytic variant of hypereosinophilic syndrome with a 17-year history of pruritus, generalized persistent papulonodular skin lesions and peripheral blood hypereosinophilia. A skin biopsy showed an eosinophil-rich infiltrate with small to medium-sized CD30+ lymphocytes and Churg-Strauss granulomas. Peripheral blood flow cytometry revealed an aberrant T-cell clone which, molecular genetically, was identical to the T-cell clone detected in the skin. No genetic aberrations of platelet-derived growth factor receptor alpha (PDGFRA), FIP1L1-PDGFRA, PDGFRB or FGFR1 were found. The skin lesions showed transient response to systemic and topical corticosteroids. The skin lesions represent cutaneous involvement by clonal T-cells in hypereosinophilic syndrome and differ from known cutaneous CD30+ lymphoproliferative disorders., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

At the intersection of atopy and autoimmunity, we present a patient with seronegative rheumatoid arthritis (RA) who developed hypereosinophilia, without evidence of other etiologies, as she became rheumatoid factor (RF) positive. Although the magnitude of eosinophilia in patients with RA has been thought to reflect the severity or activity of the RA, in our patient, eosinophilia developed at a time when the patient's synovitis was well controlled. Although eosinophilia may reflect associated drug hypersensitivity, discontinuation of the medications utilized to control our patient's disease, adalimumab and methotrexate, did not promote clinical improvement. Probably the most curious aspect of our patient was the concomitant development of rheumatoid factor seropositivity in the setting of previously seronegative RA. The temporal relationship between the development of peripheral eosinophilia and seroconversion suggests a possible connection between these events. We speculate that the T cell cytokine production that can induce eosinophilia may simultaneously activate RF production.

The CD3-CD4+ aberrant T-cell phenotype is the most described in the lymphoid variant of hypereosinophilic syndrome (L-HES), a rare form of HES. Only a few cases have been reported, and data for these patients are scarce. To describe characteristics and outcome of CD3-CD4+ L-HES patients, we conducted a national multicentric retrospective study in the French Eosinophil Network. All patients who met the recent criteria of hypereosinophilia (HE) or HES and who had a persistent CD3-CD4+ T-cell subset on blood T-cell phenotyping were included. Clinical and laboratory data were retrospectively collected by chart review. CD3-CD4+ L-HES was diagnosed in 21 patients (13 females, median age 42 years [range, 5-75 yr]). Half (48%) had a history of atopic manifestations. Clinical manifestations were dermatologic (81%), superficial adenopathy (62%), rheumatologic (29%), gastrointestinal (24%), pulmonary (19%), neurologic (10%), and cardiovascular (5%). The median absolute CD3-CD4+ T-cell count was 0.35 G/L (range, 0.01-28.3), with a clonal TCRγδ rearrangement in 76% of patients. The mean follow-up duration after HES diagnosis was 6.9 ± 5.1 years. All patients treated with oral corticosteroids (CS) (n = 18) obtained remission, but 16 required CS-sparing treatments. One patient had a T-cell lymphoma 8 years after diagnosis, and 3 deaths occurred during follow-up.In conclusion, clinical manifestations related to CD3-CD4+ T cell-associated L-HES are not limited to skin, and can involve all tissue or organs affected in other types of HE. Contrary to FIP1L1-PDGFRA chronic eosinophilic leukemia patients, CS are always effective in these patients, but CS-sparing treatments are frequently needed. The occurrence of T-cell lymphoma, although rare in our cohort, remains a major concern during follow-up.

Background: The aim of the present study was to measure eotaxin-3 (CCL26) and eotaxin-2 (CCL24) in nasal lavage fluid of patients with different forms of chronic sinonasal eosinophilic inflammation to evaluate their role in the pathophysiology of nasal hypereosinophilia., Methods: The study was an analytic cross-section study, level of evidence 3b. Patients (n = 80) with nasal hypereosinophilia were randomly recruited and grouped in the following categories: persistent allergic rhinitis (AR) (n = 25), nonallergic rhinitis with eosinophilia syndrome (NARES) (n = 30), and chronic rhinosinusitis with polyps (CRSwNP) (n = 25). Non-rhinitic volunteers (n = 20) were recruited as controls. CCL24 and CCL26 concentrations were measured by enzyme-linked immunosorbent assay (ELISA) Quantikine Human Immunoassays (R&D Systems, Minneapolis, MN) in nasal lavage fluids. Differential cell counts were performed by microscopic cytological examination of nasal tissue scraped from the inferior turbinate., Results: Mean CCL26 levels were significantly higher (p < 0.05) in AR and in NARES (132.0 pg/mL and 187.63 pg/mL, respectively) than in the control group (13.5 pg/mL); in patients with CRSwNP, CCL26 values were increased compared to controls even though the difference was not statistically significant (58.9 pg/mL vs 16.5 pg/mL). Mean CCL24 levels measured in AR, NARES, and CRSwNP were significantly increased (p < 0.05) compared to controls (96.7 pg/mL, 135.4 pg/mL, and 107.0 pg/mL, respectively, vs 32.2 pg/mL). Moreover, we observed a significant correlation between CCL24 and CCL26 levels, evaluating them intraindividually by Spearman's rank correlation test. Finally, a significant correlation was found between CCL24 and CCL26 levels and the percentage of eosinophilic infiltration of nasal mucosa., Conclusion: Our data suggest that CCL26 and CCL24 are likely involved in the pathogenesis of chronic nasal hypereosinophilia, with a complex cooperation and different involvement of the various members of eotaxin family. Further studies are necessary to better understand the actual physiopathologic mechanism, possible clinical relevance, and therapeutic implications., (© 2014 ARS-AAOA, LLC.)

Objective: To review and highlight the unappreciated roles of eosinophils suggested by recent studies., Data Sources: The literature, unpublished observations, and insights by the authors., Study Selections: Basic studies of mouse models and patient-based clinical studies of disease., Results: Eosinophils are often thought of as destructive end-stage effector cells primarily linked to parasite host defense and dysregulated immune responses associated with allergic diseases, such as asthma. However, recent studies (ie, research focused on mechanisms of action and translational studies examining disease/inflammatory pathways) are suggesting far more complex roles for eosinophils. The goal of this review is 3-fold. (1) The authors examine the dynamic history of eosinophils and how physicians over time used this information to formulate defining hypotheses. Particular emphasis is placed on recent studies challenging the parochial view of host defense in favor of roles maintaining homeostasis through immune modulation and tissue remodeling/repair. (2) They discuss diagnostic approaches to assess eosinophils in clinical settings as a means of disease identification and subsequently as a measurement of disease severity. (3) They examine how contemporary views of eosinophils and their perceived roles in diseases have led to specific therapeutic strategies. The emphasis is to review the successes and failures of these strategies as the basis of formulating future clinical studies targeting eosinophils as potential therapies of disease., Conclusion: Despite the complexities of eosinophil-mediated activities and the less than overwhelming success of initial attempts targeting these cells, eosinophils remain a potentially important focal target of disease diagnosis and subsequent treatment strategies., (Copyright © 2014 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Chronic eosinophilic leukemia (CEL) was distinguished from hypereosinophilic syndrome (HES) in the 2001 World Health Organization (WHO) criteria. Subsequently, the FIP1L1-PDGFRα (F/P) fusion tyrosine kinase was identified in patients with HES and found to be the most common clonal defect in CEL and the second most frequent mutation in systemic mastocytosis (SM). Introduction of F/P into bone marrow hematopoietic stem cells and progenitors has been used to establish murine models of F/P-myeloproliferative neoplasm and F/P-CEL. IL-5 overexpression and introduction of F/P is required to develop murine CEL. This F/P-CEL model is thought to be an accurate model of the clinical disease. Here we describe the method of F/P-CEL/SM model development and assessment.

Lymphocytic variant hypereosinophilic syndromes (L-HES) is thought to be caused by the over-production of interleukin (IL)-5 by type 2 helper cells, which leads to reactive eosinophil expansion and activation. Here we demonstrate the effect of cyclosporine in a patient with L-HES. In the present case, the surface markers of cells from resected lymph nodes or peripheral blood were analyzed by flow cytometry. Serum concentrations of IL-4, IL-5, and IL-8 were measured using an enzyme-linked immunosorbent assay. Methyl-prednisolone pulse therapy followed by the administration of 150 mg/day of cyclosporine combined with 15 mg/day of prednisolone ameliorated eosinophilia. However, abnormal CD3-CD4+ T cell clones remained even when the eosinophil count recovered to normal levels. An elevated IL-8 level was observed only when eosinophils increased. On the other hand, serum IL-4 and IL-5 levels were under detectable limits during the course. Cyclosporine was effective in decreasing the eosinophil count without the elimination of abnormal T cell clones in the present case. Cytotoxic agents may be necessary to cure this serious disease. Moreover, target therapy for IL-8 may be a new strategy for L-HES with high IL-8 and low IL-5 concentrations., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: Relapsing, refractory patients with idiopathic hypereosinophilic syndrome (I-HES) and chronic eosinophilic leukemia-not otherwise specified (CEL-NOS) do not have many effective, durable therapeutic options. Alemtuzumab, an anti-CD52 antibody, has been reported to be an effective therapy due to inherent expression of CD52 on eosinophils., Methods: A retrospective chart review of 12 patients treated with alemtuzumab at our center until 2012., Results: Ten (83%) of 12 patients achieved complete hematologic response (CHR) after a median of 1 week for a median duration of 66 weeks, with the elimination of disease-related symptoms; 2 patients achieved partial hematologic remission hematologic remission (PHR). Patients with CHR who received alemtuzumab maintenance (n = 5) had a significantly longer time to progression than those patients who were only observed (n = 5) (P = .01). Eleven patients relapsed (only one while on maintenance), and 6 were rechallenged with alemtuzumab. Five (83%) achieved second CHR after a median of 3.5 weeks, for a median duration of 123 weeks. Again, those given maintenance (n = 3) had a longer time to progression than those who were only observed (P = .04). Adverse effects were mostly related to infusion reactions and lymphopenia-related viral infections (despite antibiotic prophylaxis). One patient developed Epstein-Barr virus-related lymphoma., Conclusions: Alemtuzumab is an effective treatment for patients with relapsed, refractory idiopathic hypereosinophilic syndrome and chronic eosinophilic leukemia-not otherwise specified, in terms of both CHR achievement (even after repeated rechallenges) and duration (particularly if provided as a maintenance therapy). Common adverse effects are related to infusion reactions and immunosuppression., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background: The recent development of eosinophil-targeting agents has raised enthusiasm for management of patients with hypereosinophilic syndromes. Roughly half of anti-IL-5-treated patients with corticosteroid-responsive lymphocytic (L-HES) and idiopathic disease variants can be tapered off corticosteroids. Potential consequences of corticosteroid-withdrawal on clonal expansion of pre-malignant CD3⁻CD4⁺ T-cells associated with L-HES are a subject of concern. Indeed, corticosteroid treatment inhibits T-cell activation and may lower blood CD3⁻CD4⁺ cell counts. On the other hand, previous studies have shown that eosinophils support CD4 T-cell activation, suggesting that targeted eosinophil depletion may negatively regulate these cells., Objectives: Effects of eosinophils on CD4 T-cell activation in vitro were investigated as an indirect means of exploring whether treatment-induced eosinophil depletion may affect pathogenic T-cells driving L-HES., Methods: Helper (CD4) T-cells and CD3⁻CD4⁺ cells from healthy controls and L-HES patients, respectively, were cultured in vitro in presence of anti-CD3/CD28 or dendritic cells. Effects of eosinophils on T-cell proliferation and cytokine production were investigated., Results: Eosinophils enhanced CD3-driven proliferation of CD4 T-cells from healthy subjects in vitro, while inhibiting TCR-independent proliferation and IL-5 production by CD3⁻CD4⁺ T-cells., Conclusions: While this study confirms previous work showing that eosinophils support activation of normal helper T-cells, our in vitro findings with CD3⁻CD4⁺ T-cells suggest that eosinophil-depletion may favor activation and expansion of this pathogenic lymphocyte subset. With the ongoing development of eosinophil-targeted therapy for various eosinophilic conditions, the indirect consequences of treatment on the underlying immune mechanisms of disease should be investigated in detail in the setting of translational research programs.

Background: Hypereosinophilic syndromes (HESs) are chronic disorders that require long-term therapy to suppress eosinophilia and clinical manifestations. Corticosteroids are usually effective, yet many patients become corticosteroid refractory or develop corticosteroid toxicity. Mepolizumab, a humanized monoclonal anti-IL-5 antibody, showed corticosteroid-sparing effects in a double-blind, placebo-controlled study of FIP1L1/PDGFRA-negative, corticosteroid-responsive subjects with HESs., Objective: We evaluated long-term safety and efficacy of mepolizumab (750 mg) in HES., Methods: MHE100901 is an open-label extension study. The primary end point was the frequency of adverse events (AEs). Optimal dosing frequency, corticosteroid-sparing effect of mepolizumab, and development of antimepolizumab antibodies were also explored., Results: Seventy-eight subjects received 1 to 66 mepolizumab infusions each (including mepolizumab infusions received in the placebo-controlled trial). Mean exposure was 251 weeks (range, 4-302 weeks). The most common dosing interval was 9 to 12 weeks. The incidence of AEs was 932 events per 100 subject-years in the first year, declining to 461 events per 100 subject-years after 48 months. Serious AEs, including 1 death, were reported by the investigator as possibly due to mepolizumab in 3 subjects. The median daily prednisone dose decreased from 20.0 to 0 mg in the first 24 weeks. The median average daily dose for all subjects over the course of the study was 1.8 mg. Sixty-two percent of subjects were prednisone free without other HES medications for ≥ 12 consecutive weeks. No neutralizing antibodies were detected. Twenty-four subjects withdrew before study completion for death (n = 4), lack of efficacy (n = 6), or other reasons., Conclusion: Mepolizumab was well tolerated and effective as a long-term corticosteroid-sparing agent in PDGFRA-negative HES., (Published by Mosby, Inc.)