Hematologic Malignancies Identified in Patients with Hypereosinophilia and Hypereosinophilic Syndromes

Managing Patients with Hypereosinophilic Syndrome: A Statement from the Italian Society of Allergy, Asthma, and Clinical Immunology (SIAAIC)

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.

Tissue Eosinophilia in B-cell Lymphoma: An Underrecognized Phenomenon

Tissue eosinophilia is seldom reported in B-cell lymphoma. It poses diagnostic challenges and frequently leads to the consideration of other diagnoses, particularly T-cell lymphomas. The scarce literature underscores the need for in-depth studies to enhance awareness and understanding of this phenomenon. We investigated 54 cases of B-cell lymphoma with notable tissue eosinophils, analyzing clinical information, hematoxylin and eosin staining, immunohistochemistry, and PCR-based clonality analysis. Nodal marginal zone lymphoma (NMZL) emerged as the most prevalent type (n=26), followed by B-cell lymphoma, not otherwise specified (n=13), diffuse large B-cell lymphoma (n=10), follicular lymphoma (n=2), chronic lymphocytic leukemia/small lymphocytic lymphoma (n=1), extranodal marginal zone lymphoma (n=1), and primary cutaneous marginal zone lymphoma (n=1). Shared features across different lymphoma types, best exemplified by NMZL, included plasmacytic differentiation (57.7%), increased vascularity (84.6%) with a tendency for perivascular distribution of neoplastic cells, and a tumor microenvironment abundant in T cells and histiocytes; some cases showed increased PD-1-positive cells. These features often raise consideration of angioimmunoblastic T-cell lymphoma. Along with clonality analysis, features supporting the diagnosis of B-cell lymphoma included cytological atypia in B cells rather than T cells, and the lack of follicular dendritic cell meshwork expansion. In addition, diffuse large B-cell lymphoma frequently exhibited interfollicular distribution and monocytoid appearance, indicating the possibility of transformed NMZL. Collectively, tissue eosinophilia can occur in diverse B-cell lymphomas but is most prevalent in tumors with a postgerminal stage of differentiation.

Biologic therapies for hypereosinophilic disorders: From tyrosine kinase inhibitors to monoclonal antibodies. Towards an increasingly customized management?

Hypereosinophilic syndromes (HES) encompass a wide range of disorders characterized by persistent peripheral blood hypereosinophilia (HE) (i.e., an eosinophil count ≥1.5 × 10⁹/L and ≥ 10% eosinophils preferably with a minimal duration of 6 months if documentation is available) associated with organ damage and/or dysfunction attributable to tissue eosinophilic infiltrate and release of granule contents. In most cases, HE is associated with atopic conditions/allergies, parasitic infections, medications, autoimmune disorders and/or solid tumors in most cases. More rarely, it can be one of the dominant manifestations of an underlying myeloid/lymphoid neoplasm. With regard to hematological forms, in recent decades the advances in understanding the pathogenic aspects of HES have led to a growing interest in these diseases, and in the 2016 WHO classification multiple subgroups were defined according to the molecular profile with the aim of better characterizing these syndromes and establishing which patients will benefit from specific pharmacological targeted therapies. This review article will provide a comprehensive overview of possible therapeutic approaches for HES in the light of each specific molecular alteration, considering both tyrosine kinase inhibitors and monoclonal antibodies, either implemented in clinical practice or currently still under development.

Clinical analysis of hypereosinophilic syndrome first presenting with asthma-like symptoms

INTRODUCTION

Clinical manifestations of hypereosinophilic syndrome (HES) are diverse. This study aimed to summarise these clinical characteristics with asthma-like onset as the first symptom, and compare these characteristics and treatment strategies between idiopathic and parasitic HES.

MATERIALS AND METHODS

We retrospectively analysed 36 HES patients with asthma-like symptoms as the first episode, between January 2013 and October 2019. Data of patients with HES of an unknown cause (idiopathic HES) and parasitic infection (parasite HES) were analysed.

RESULTS

The idiopathic and parasite HES groups included 16 and 20 patients, respectively, with more males in the parasite HES group (p < .05). Wheezing and dry rales was the most common symptom and signs, with no significant differences in symptoms and signs between the groups. The most often misdiagnosed disease was bronchial asthma. The peripheral blood eosinophil count was significantly increased compared with normal counts in both groups (p > .05). Abnormal pulmonary function is mainly manifested as obstructive ventilatory disorder and mixed ventilatory disorder. Chest computed tomography showed extensive ground-glass exudation, patches, consolidation, nodules, and pleural effusion. Histopathological examination showed eosinophilic infiltration without vasculitis or granuloma. Glucocorticoids had a significant therapeutic effect, and the parasite HES group required combined deworming drugs. The duration of corticosteroids therapy in the idiopathic HES group was significantly longer than that in the parasite HES group (p < .05). The overall prognosis was good, and 81.25% of the patients were clinically cured in the parasite HES group; however, relapse occurred easily in the idiopathic HES group.

CONCLUSIONS

Asthma-like symptoms, obstructive ventilatory disorder or positive bronchial dilation test, and poor response to inhaled corticosteroids are not necessarily indicative of refractory asthma; HES should be considered. The clinical characteristics of HES of different aetiologies are similar. Systemic corticosteroid therapy is preferred for idiopathic and parasitic infections. Idiopathic HES is treated with prolonged corticosteroids and relapses easily.Key MessagesAsthma-like symptoms, obstructive ventilatory disorder or positive bronchial dilation tests, and poor responses to inhaled corticosteroids are not necessarily indicative of refractory asthma, and hypereosinophilic syndrome should be considered.The clinical characteristics of hypereosinophilic syndrome of different aetiologies are similar, and systemic glucocorticoid therapy is preferred for both idiopathic and parasitic infections.Idiopathic hypereosinophilic syndrome is treated with prolonged corticosteroids and relapses easily.

Intra-abdominal Mass, Obstructive Jaundice, and Eosinophilia

Eosinophilic granulomatosis with polyangiitis(EGPA) is a systemic vasculitis syndrome associated with eosinophilia, which most commonly involves the lung, skin, cardiovascular, gastrointestinal, renal, and peripheral nervous systems (PNS). We report a case of a 48-year-old man presented as obstructive jaundice caused by intra-abdominal mass, and he also had elevated peripheral eosinophils. The pathological features of the mass included vasculitis and eosinophils infiltration. At first he was diagnosed as EGPA and treated by glucocorticoid and cyclophosphamide. The patient did not get complete response after six months and then the repeat biopsy proved that he had non-Hodgkin's lymphoma.

Clinical Characteristics and Outcomes of Eosinophilic Colitis in Patients With Cancer

BACKGROUND

Eosinophilic colitis (EoC) is a rare form of eosinophilic gastrointestinal disease characterized by diffuse eosinophilic infiltration in the deep lamina propria of colonic mucosa. The pathophysiology is unclear, but EoC has been associated with multiple known risk factors.

AIM

The aim of this study was to characterize the clinical characteristics and disease course of patients with EoC at a major cancer center.

MATERIAL AND METHODS

We retrospectively reviewed colonic samples obtained between January 2000 and December 2018 from our institutional database and included cases with significant colonic eosinophilia. Baseline clinical data and EoC-related clinical course and outcomes were documented.

RESULTS

Forty-one patients were included. One fourth had coexisting autoimmune conditions. Seventy-eight percent had a cancer diagnosis. Half the patients received chemotherapy, with a median duration of 180 days between chemotherapy and EoC onset. Symptoms were present in 76% of patients. Diarrhea was more prevalent in patients who received chemotherapy (85% vs. 42%). Median duration of EoC symptoms was 30 days in patients with cancer and 240 days in those without cancer (P=0.03). Most patients (88%) had normal colonoscopy findings. Fifteen percent of patients required hospitalization. All-cause mortality was 37%, mostly related to underlying malignancy and organ failure.

CONCLUSIONS

EoC in cancer patients appears to have more diarrhea-predominant symptoms, particularly in patients receiving chemotherapy, but a shorter disease duration compared with patients without cancer. Hospitalization can be required for serious cases. Treatment may be reserved for patients requiring symptom management, as most patients with EoC have good clinical outcomes regardless of treatment.

The role of eosinophils in immunotherapy

PURPOSE OF REVIEW

The purpose of this review is to provide a brief discussion on the differential diagnosis for peripheral eosinophilia. We will then focus on targeted immunotherapies for atopic disease, their effects on absolute peripheral eosinophil counts, and use of peripheral eosinophils as a predictor of treatment response.

RECENT FINDINGS

In atopic disease, lower absolute peripheral eosinophil counts are typically associated with improved outcomes. Much of the current evidence on eosinophils as a biomarker comes from post-hoc analyses in therapeutic immunotherapy. While changes in eosinophilia were not the primary outcome of interest in many studies, some patterns did emerge. Cytolytic mAbs AK002 and benralizumab completely reduce peripheral and tissue eosinophil numbers. Dupilumab may have paradoxical transient eosinophilia despite observed clinical efficacy.

SUMMARY

Atopic inflammation is complex largely due to the various cytokines which affect eosinophils activation, proliferation, differentiation, and survival. This demonstrates the challenges of using peripheral eosinophilia alone as a biomarker for atopic disease activity. More attention should spotlight how different immunotherapy modalities affect eosinophil-driven responses.

Eosinophils as Major Player in Type 2 Inflammation: Autoimmunity and Beyond

Eosinophils are a subset of differentiated granulocytes which circulate in peripheral blood and home in several body tissues. Along with their traditional relevance in helminth immunity and allergy, eosinophils have been progressively attributed important roles in a number of homeostatic and pathologic situations. This review aims at summarizing available evidence about eosinophils functions in homeostasis, infections, allergic and autoimmune disorders, and solid and hematological cancers.Their structural and biological features have been described, along with their physiological behavior. This includes their chemokines, cytokines, granular contents, and extracellular traps. Besides, pathogenic- and eosinophilic-mediated disorders have also been addressed, with the aim of highlighting their role in Th2-driven inflammation. In allergy, eosinophils are implicated in the pathogenesis of atopic dermatitis, allergic rhinitis, and asthma. They are also fundamentally involved in autoimmune disorders such as eosinophilic esophagitis, eosinophilic gastroenteritis, acute and chronic eosinophilic pneumonia, and eosinophilic granulomatosis with polyangiitis. In infections, eosinophils are involved in protection not only from parasites but also from fungi, viruses, and bacteria. In solid cancers, local eosinophilic infiltration is variably associated with an improved or worsened prognosis, depending on the histotype. In hematologic neoplasms, eosinophilia can be the consequence of a dysregulated cytokine production or the result of mutations affecting the myeloid lineage.Recent experimental evidence was thoroughly reviewed, with findings which elicit a complex role for eosinophils, in a tight balance between host defense and tissue damage. Eventually, emerging evidence about eosinophils in COVID-19 infection was also discussed.

Reactive Eosinophil Proliferations in Tissue and the Lymphocytic Variant of Hypereosinophilic Syndrome

OBJECTIVES

The 2019 Society for Hematopathology and European Association for Haematopathology Workshop reviewed the spectrum of neoplastic, nonneoplastic, and borderline entities associated with reactive eosinophilia in tissue.

METHODS

The workshop panel reviewed 46 cases covered in 2 workshop sessions.

RESULTS

The 46 cases were presented with their consensus diagnoses during the workshop. Reactive eosinophilia in lymph nodes and other tissues may be accompanied by or be distinct from peripheral blood eosinophilia. Reactive etiologies included inflammatory disorders such as Kimura disease and IgG4-related disease, which may show overlapping pathologic features and reactions to infectious agents and hypersensitivity (covered in a separate review). Hodgkin, T-cell, and B-cell lymphomas and histiocytic neoplasms can result in reactive eosinophilia. The spectrum of these diseases is discussed and illustrated through representative cases.

CONCLUSIONS

Reactive eosinophilia in lymph nodes and tissues may be related to both nonneoplastic and neoplastic lymphoid proliferations and histiocytic and nonhematolymphoid processes. Understanding the differential diagnosis of reactive eosinophilia and the potential for overlapping clinical and pathologic findings is critical in reaching the correct diagnosis so that patients can be treated appropriately.

Le N, Steele R. A 79-year-old man with persistent eosinophilia and elevated immunoglobulin E

The differential diagnoses for eosinophilia include allergic, infectious, autoimmune, and neoplastic diseases. We presented the case of a 79-year-old man with eosinophilia and elevated immunoglobulin E that persisted despite adequate treatment for possible environmental exposures. Further specialized testing based on his initial workup led to his diagnosis. This case highlights the importance of sequential and targeted testing to evaluate for rare causes of eosinophilia.

Ulcerative Colitis in Hematological Malignancies: Paraneoplastic Manifestation or Coincidental Bystander?

Evidence of coexistence of diverse hematological malignancies—lymphoma, leukemia, multiple myeloma, and myelodysplastic syndromes—and either ulcerative colitis or Crohn's disease can be found in the literature. However, a more “systemic” effort to reach further and examine the potential of either one as paraneoplastic manifestation has not been performed. Based on these, three cases of ulcerative colitis manifesting before, simultaneously, and after the onset of different hematological malignancies are presented and critically evaluated.

The Role of Eosinophils in Immunotherapy

PURPOSE OF REVIEW

The purpose of this review is to provide a brief discussion on the differential diagnosis for peripheral eosinophilia. We will then focus on targeted immunotherapies for atopic disease, their effects on absolute peripheral eosinophil counts, and use of peripheral eosinophils as a predictor of treatment response.

RECENT FINDINGS

In atopic disease, lower absolute peripheral eosinophil counts are typically associated with improved outcomes. Much of the current evidence on eosinophils as a biomarker comes from post hoc analyses in therapeutic immunotherapy. While changes in eosinophilia were not the primary outcome of interest in many studies, some patterns did emerge. Cytolytic monoclonal antibodies AK002 and benralizumab completely reduce peripheral and tissue eosinophil numbers. Dupilumab may have paradoxical transient eosinophilia despite observed clinical efficacy. Atopic inflammation is complex largely due to the various cytokines which affect eosinophil activation, proliferation, differentiation, and survival. This demonstrates the challenges of using peripheral eosinophilia alone as a biomarker for atopic disease activity. More attention should spotlight how different immunotherapy modalities affect eosinophil-driven responses.

Hypereosinophilic syndromes in the precision medicine era: clinical, molecular aspects and therapeutic approaches (targeted therapies)

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.

A multimodality work-up of patients with Hypereosinophilia

The work-up of patients with hypereosinophilia (HE) is complex. Following the recently revised World Health Organization criteria, we retrospectively reviewed 125 patients who were referred to us to exclude a neoplastic cause of HE (2003-2016). The clinical laboratory work-up confirmed secondary HE in 25 (20%) patients; myeloid/lymphoid neoplasms with rearrangements of PDGFRA (n = 9) or PDGFRB (n = 2) (9%); HE associated with a well-defined myeloid neoplasm in 8 (6%); and abnormal bone marrow and/or molecular genetic abnormalities consistent with chronic eosinophilic leukemia (CEL), not otherwise specified (NOS) in 21 (17%) patients. For the remaining 60 (48%) patients, a specific diagnosis was not identified, and 56 patients had HE related findings consistent with idiopathic hypereosinophilic syndrome (HES), while 4 patients who were asymptomatic. With a median follow up of 35.3 months (range, <1-104), patients with CEL, not otherwise specified (NOS) had a median OS of 26.1 months, significantly inferior to patients with idiopathic HES (not reached, P < .01). Thus, our experience in a single tertiary cancer center shows that the work-up of HE following WHO recommendations requires a multimodality-based approach; and a correct diagnosis determines risk stratification and proper patient management. However, the causes of HE remain unknown in approximately half of referred patients, indicating the need for further studies.

Consultation for Elevated Blood Eosinophils: Clinical Presentations, High Value Diagnostic Tests, and Treatment Options

The workup of a patient found to have eosinophilia should follow a thorough path with a detailed history and physical examination aimed at eliciting eosinophilic organ involvement, followed by histological confirmation whenever possible. The differential diagnosis of hypereosinophilia is extensive, but a rational approach beyond the history and physical examination including serologic, blood, and bone marrow cell analyses, genetic testing, and radiologic imaging can distinguish many of the causes. Often input from specialists (eg, hematology, dermatology, pulmonary, gastroenterology, and neurology) can help narrow down the possibilities and eventually result in a specific diagnosis. An accurate diagnosis is key to choosing the optimal treatment for a particular condition, and this is certainly true for eosinophilic disorders. Myeloid neoplasms that present with eosinophilia, for example, may respond to medicines that the allergist may be less accustomed to using, such as immunosuppressive agents and kinase inhibitors. Similarly, newly approved biologics that target IL-5 and eosinophils may provide new options for management. What follows is a case-based approach that helps to underscore key features of diagnosis, management, and follow-up when faced with a patient with a potential eosinophil-related disorder.

Biologic Agents for the Treatment of Hypereosinophilic Syndromes

Hypereosinophilic syndromes (HES) are a heterogeneous group of rare disorders defined by the presence of marked peripheral or tissue eosinophilia resulting in end-organ damage. Although conventional therapies, including glucocorticoids, hydroxyurea, and IFN-α, are initially effective in reducing eosinophilia and symptoms in a majority of patients with platelet-derived growth factor mutation-negative HES, the development of resistance and treatment-related toxicity are common. In contrast, targeted therapy with the tyrosine kinase inhibitor, imatinib, is well tolerated but effective only in the subset of patients with HES with a primary myeloid disorder. Eosinophil-targeted biotherapeutics offer the potential of improved efficacy with few, if any, adverse effects. The aims of this review are to provide an overview of current approaches to the use of conventional HES therapies and a discussion of existing biotherapeutics that target eosinophils and their potential use in the treatment of HES. With the continuing expansion of eosinophil-targeted biotherapeutics, the future for patients with eosinophilic disorders is promising.

Diagnosis and Novel Approaches to the Treatment of Hypereosinophilic Syndromes

PURPOSE OF REVIEW

Hypereosinophilic syndrome (HES) is characterized by persistent hypereosinophilia associated with end-organ damage. As our understanding of the pathogenesis of various forms of HES broadens, so does our ability to tailor steroid-sparing therapies for each subtype. The purpose of this review is to summarize recent literature related to the etiology, diagnosis, and management of HES.

RECENT FINDINGS

Mutations involved in subsets of HES can guide the choice of tyrosine kinase inhibitors beyond just imatinib. Several biologics that target interleukin-5 or its receptor have shown beneficial and selective eosinophil-reducing effects in clinical trials for asthma and other disorders including HES. Early clinical data with emerging therapies such as dexpramipexole and anti-Siglec-8 antibody show promise, but need to be confirmed in randomized trials. Several new biologics and tyrosine kinase inhibitors have been shown to lower eosinophil numbers, but more randomized trials are needed to confirm efficacy in HES.

Hypereosinophilic syndrome preceding a diagnosis of B-cell lymphoma

INTRODUCTION

Hypereosinophilic syndrome (HES) is a rare condition characterized by eosinophilia and organ destruction secondary to eosinophilic infiltration. The coexistence of primary B-cell lymphoma and hypereosinophilic syndrome is extremely rare. We present a case of HES that preceded the diagnosis of diffuse large B-cell lymphoma.

CASE REPORT

A 70-year-old man presented with a 3-month history of diarrhea and 30-pound weight loss. Complete blood count showed a white blood cell count of 7452/µL with eosinophils of 42% (absolute eosinophil count 3130). Colonoscopy showed eosinophilic infiltrate in the lamina propria and muscularis mucosa. Bone marrow biopsy showed elevated myeloid: erythroid ratio (6:1), increased mature and immature eosinophilic infiltration (10% of nucleated cells). Molecular studies were negative for Fip1-like1-platelet-derived growth factor receptor alpha (FIP1L1-PDGFRA) translocation and PDGFRB and FGFR mutations, indicating nonclonal eosinophilia. Treatment was initiated with prednisone (1 mg/kg) and hydroxyurea 500 mg twice daily. He responded with complete resolution of symptoms. Five months later, the patient presented with right lower quadrant pain. Abdominal/pelvis computed tomography (CT) showed bulky right inguinal lymphadenopathy and biopsy revealed CD10+ diffuse large B-cell lymphoma (DLBCL). Further staging workup showed the stage to be IIB. He received 6 cycles of chemotherapy and involved field radiation therapy. He achieved complete remission.

CONCLUSION

Reviewing the literature indicates only one case of similar presentation with concomitant HES and DLBCL. Eosinophilia is routinely encountered in clinical practice and as such physicians must be aware of the rarer, more malevolent underlying associations of this condition so as to aid early diagnosis and prompt treatment.

Safety of humanized monoclonal antibodies against IL-5 in asthma: focus on reslizumab

INTRODUCTION

Reslizumab, a humanized mAb against IL-5, reduces the number of eosinophils in the blood and lungs. Based on efficacy and safety data from pivotal RCTs, reslizumab had been approved for use as an add-on maintenance treatment of severe asthma with an eosinophilic phenotype in adults who have a history of exacerbations despite receiving their current asthma medicines. Areas covered: Current literature on reslizumab has been reviewed with a specific focus on its safety profile in the treatment of severe asthma. Expert opinion: Large pivotal and supportive trials reinforce the view that reslizumab is well tolerated, with an acceptable safety profile in patients exposed for longer than 2 years. However, no or few data concerning safety in special populations such as smokers, those with immune- and cellular senescence, patients with comorbidities and those receiving multi-drug treatments are available as yet. Furthermore, we need to fully elucidate some fundamental issues such as the risk of anaphylaxis and the long-term risk-benefit ratio of the impact of depletion of eosinophils and the potential risk of malignancies induced by a treatment with this anti-IL-5 agent.

Peripheral T-cell lymphoma mimicking classic Hodgkin's lymphoma in a patient presenting with fevers of unknown origin

A 52-year-old man presented to our hospital for further workup of fever of unknown origin after an extensive workup at an outside hospital had failed to reveal a diagnosis. At the outside hospital, he underwent excisional biopsy of the left supraclavicular lymph node, which showed non-necrotising granulomatous changes, and a bone marrow biopsy which showed a normocellular marrow. He was discharged without a diagnosis with recommendations to present to a tertiary hospital. During his admission, his hospital course was complicated by new direct hyperbilirubinaemia and eosinophilia, prompting liver and skin biopsies which showed CD30+ and CD3+ cells. He subsequently underwent left axillary lymph node biopsy, which was reported as 'classic Hodgkin's lymphoma'. With worsening lab values and T cells noted on liver and skin biopsies, excisional lymph node biopsy was sent to the National Institute of Health, where it was confirmed patient had peripheral T cell lymphoma.

Eosinophils and eosinophil-associated diseases: An update

The goal of this series is to offer a survey of the latest literature for clinicians and scientists alike, providing a list of important recent advances relevant to the broad field of allergy and immunology. This particular assignment was to cover the topic of eosinophils. In an attempt to highlight major ideas, themes, trends, and advances relevant to basic and clinical aspects of eosinophil biology, a search of articles published since 2015 in the Journal of Allergy and Clinical Immunology and other high-impact journals was performed. Articles were then reviewed and organized, and then key findings were summarized. Given space limitations, many outstanding articles could not be included, but the hope is that what follows provides a succinct overview of recently published work that has significantly added to our knowledge of eosinophils and eosinophil-associated diseases.

A diagnostic protocol designed for determining allergic causes in patients with blood eosinophilia

BACKGROUND

Blood eosinophilia is a common laboratory abnormality, and its characterization frequently represents a quandary for primary care physicians. Consequently, in France, specialists and particularly hematologists, often must investigate patients who present with blood eosinophilia that often, but not always, occurs because of allergic causes. Both the Departments of Hematology and Parasitology at Toulouse University Hospitals established a collaboration to rule out allergic causes of eosinophilia, particularly helminthiases, prior to initiating more sophisticated investigations.

METHODS

Since 2004, the authors employed the same protocol to investigate eosinophilic outpatients who attended the clinic of Parasitology at Toulouse University Hospitals, and they reported the performance of this diagnostic procedure that was designed to be rapid (no hospitalization required) and only moderately expensive.

RESULTS

A total of 406 patients who presented with blood eosinophilia greater than 0.5 (×109, giga cells per litter, G/L) had an allergic etiology in 350 (86.2%) cases. Among the remaining 56 subjects, 17 did not undergo a follow-up and 39 were referred to another specialized department, mostly Hematology. However, only 21 patients attended then were subsequently investigated. Non-allergic causes of eosinophilia, including 3 cases of the lymphoid variant of hypereosinophilic syndrome and 2 cases of myeloproliferative disorder, were identified in 14 patients, whereas 7 remained diagnosed as having idiopathic eosinophilia.

CONCLUSION

This study underlines the need to investigate patients presenting with even moderate blood eosinophilia. The work-up that was employed appears to be efficient and versatile and may be used by any medical specialist, such as in hematology, infectious disease, or internal medicine departments, who needs to investigate eosinophilic patients and should initially rule out any etiology of allergic eosinophilia.