Elevated serum tryptase levels identify a subset of patients with a myeloproliferative variant of idiopathic hypereosinophilic syndrome associated with tissue fibrosis, poor prognosis, and imatinib responsiveness

World Health Organization and International Consensus Classification of eosinophilic disorders: 2024 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

The eosinophilias encompass a broad range of non-hematologic (secondary or reactive) and hematologic (primary or clonal) disorders with the potential for end-organ damage.

DIAGNOSIS

Hypereosinophilia (HE) has generally been defined as a peripheral blood eosinophil count greater than 1.5 × 109/L, and may be associated with tissue damage. After the exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on a combination of various tests. They include morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ hybridization, molecular testing and flow immunophenotyping to detect histopathologic or clonal evidence for an acute or chronic hematolymphoid neoplasm.

RISK STRATIFICATION

Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2022 World Health Organization and International Consensus Classification endorse a semi-molecular classification scheme of disease subtypes. This includes the major category "myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions" (MLN-eo-TK), and the MPN subtype, "chronic eosinophilic leukemia" (CEL). Lymphocyte-variant HE is an aberrant T-cell clone-driven reactive eosinophila, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion.

RISK-ADAPTED THERAPY

The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (e.g., <1.5 × 109/L) without symptoms or signs of organ involvement, a watch and wait approach with close follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Pemigatinib was recently approved for patients with relapsed or refractory FGFR1-rearranged neoplasms. Corticosteroids are first-line therapy for patients with lymphocyte-variant HE and HES. Hydroxyurea and interferon-α have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES. Mepolizumab, an interleukin-5 (IL-5) antagonist monoclonal antibody, is approved by the U.S Food and Drug Administration for patients with idiopathic HES. Cytotoxic chemotherapy agents, and hematopoietic stem cell transplantation have been used for aggressive forms of HES and CEL, with outcomes reported for limited numbers of patients. Targeted therapies such as the IL-5 receptor antibody benralizumab, IL-5 monoclonal antibody depemokimab, and various tyrosine kinase inhibitors for MLN-eo-TK, are under active investigation.

The Clinical Features of Hereditary Alpha-Tryptasemia

BACKGROUND

Hereditary alpha-tryptasemia (HAT) is a genetic predisposition of autosomal dominant inheritance that leads to a high normal (≥ 8-11.4 μg/L) or pathologically elevated (>11.4 μg/L) basal serum tryptase (BST) concentration. Its prevalence in the United Kingdom and France is reportedly 5%-6%; its prevalence in Germany is unknown. Symptomatic persons with HAT suffer from a complex constellation of symptoms. As described in this review, HAT is an important differential diagnosis in interdisciplinary practice.

METHODS

This review is based on publications about HAT retrieved by a selective search in PubMed, on relevant presentations at scientific meetings, and on our clinical experience. We also collected our own data on the prevalence and clinical manifestations of HAT.

RESULTS

According to the literature, HAT is very common among patients in medical centers with BST values of 8 μg/L or above (64-74%). HAT is most commonly associated with neuropsychiatric symptoms such as exhaustion (85%), depressive episodes (59%), sleep disturbances (69%), and memory impairment (59%-68%), followed by gastrointestinal symptoms such as irritable bowel (30%-60%), nausea (51%), and reflux (49%-77%). Typical mast cell-mediated symptoms, such as flushing (47%), itch (69%), urticaria (37%), and anaphylaxis (14%-28%), are reported as well. Less commonly reported are cardio vascular manifestations, such as hypotonia, dizziness, and tachycardia (34%), and joint hyper - mobility (28%). HAT is more common among patients with systemic mastocytosis (SM; 12%-21%). It is often associated with severe anaphylaxis induced by insect toxins or unknown triggers. The therapeutic options include treatment with antihistamines, mastcell stabilizers, or IgE antibodies.

CONCLUSION

A diagnosis of hereditary alphatryptasemia can be strongly suspected on the basis of thorough history-taking and BST measurement and then confirmed by molecular genetic testing.

In-Depth Review of Loeffler Endocarditis: What Have We Learned?

Loeffler endocarditis, eosinophilic endocarditis or eosinophilic endomyocardial disease are conditions associated with hypereosinophilia and they affect the heart function. Loeffler endocarditis is a rare endomyocardial disorder thought to be caused by eosinophilic damage. The disorder is characterized by inflammatory infiltration, formation of thrombus within cardiovascular system, and ultimately fibrosis of the afflicted area. It can lead to multiple severe complications, including thromboembolic disease, thickening of fibrous tissue in the endocardium of ventricles, valve involvement, apical obliteration, and various heart disorders. Although early clinical intervention can lead to remission, the underlying mechanisms of the disorder remain unresolved. In the present article, we summarise the existing literature concerning Loeffler endocarditis based on PubMed, Web of Science, and other medical databases to conduct an in-depth review of the epidemiology, etiology, pathophysiological mechanisms, staging, diagnosis, treatment and prognosis of Loeffler endocarditis. Meanwhile, we provide novel patients data and clinical figures of Loeffler endocarditis to supplement the understanding of this cardiac disorder. The findings presented in this article provide a basis for further studies and can be used to improve management of the disorder.

The Normal Range of Baseline Tryptase Should Be 1 to 15 ng/mL and Covers Healthy Individuals With HαT

Physiological levels of basal serum tryptase vary among healthy individuals, depending on the numbers of mast cells, basal secretion rate, copy numbers of the TPSAB1 gene encoding alpha tryptase, and renal function. Recently, there has been a growing debate about the normal range of tryptase because individuals with the hereditary alpha tryptasemia (HαT) trait may or may not be symptomatic, and if symptomatic, uncertainty exists as to whether this trait directly causes clinical phenotypes or aggravates certain conditions. In fact, most HαT-positive cases are regarded as asymptomatic concerning mast cell activation. To address this point, experts of the European Competence Network on Mastocytosis (ECNM) and the American Initiative in Mast Cell Diseases met at the 2022 Annual ECNM meeting and discussed the physiological tryptase range. Based on this discussion, our faculty concluded that the normal serum tryptase range should be defined in asymptomatic controls, inclusive of individuals with HαT, and based on 2 SDs covering the 95% confidence interval. By applying this definition in a literature screen, the normal basal tryptase in asymptomatic controls (HαT-positive persons included) ranges between 1 and 15 ng/mL. This definition should avoid overinterpretation, unnecessary referrals, and unnecessary anxiety or anticipatory fear of illness in healthy individuals.

Idiopathic hypereosinophilic syndrome presenting as cardiac tamponade and multiorgan dysfunction

Idiopathic hypereosinophilic syndrome is characterised by the overproduction of eosinophils with tissue infiltration, leading to multiorgan dysfunction. Its heterogenous presentation makes the diagnosis challenging and easy to miss. A woman in her 70s was admitted with chest pain and shortness of breath. Diagnostic testing showed elevated cardiac enzymes, an ejection fraction of 45% and pericardial effusion. Pericardiocentesis helped her symptoms significantly. Cardiac catheterisation revealed patent coronary arteries. She was diagnosed with myopericarditis and discharged on non-steroidal anti-inflammatory drugs. She returned the following week with worsening chest pain, dyspnoea and diarrhoea. Chest imaging showed bilateral infiltrates. Diagnostic testing showed eosinophilic predominance in peripheral blood (59%), pericardial fluid (37%) and bronchoalveolar lavage (31%). After a negative infectious workup, she was started on glucocorticoids and responded favourably. She was discharged on steroids. Mepolizumab was initiated outpatient, and steroids were discontinued. Mepolizumab was discontinued after 2 years while monitoring her symptoms and eosinophil counts.

False-Negative Testing for FIP1L1::PDGFRA by Fluorescence in situ Hybridization Is a Frequent Cause of Diagnostic Delay

The imatinib-sensitive fusion gene FIP1L1::PDGFRA is the most frequent molecular abnormality identified in patients with eosinophilic myeloid neoplasms. Rapid recognition of this mutation is essential given the poor prognosis of PDGFRA-associated myeloid neoplasms prior to the availability of imatinib therapy. We report a case of a patient in whom delayed diagnosis resulted in cardiac transplantation for eosinophilic endomyocardial fibrosis. The delay in diagnosis was due, in part, to a false-negative result in fluorescence in situ hybridization (FISH) testing for FIP1L1::PDGFRA. To explore this further, we examined our cohort of patients presenting with confirmed or suspected eosinophilic myeloid neoplasms and found 8 additional patients with negative FISH results despite a positive reverse-transcriptase polymerase chain reaction test for FIP1L1::PDGFRA. More importantly, false-negative FISH results delayed the median time to imatinib treatment by 257 days. These data emphasize the importance of empiric imatinib therapy in patients with clinical features suggestive of PDGFRA-associated disease.

Secretory and Membrane-Associated Biomarkers of Mast Cell Activation and Proliferation

Mast cells (MCs) are immune cells distributed in many organs and tissues and involved in the pathogenesis of allergic and inflammatory diseases as a major source of pro-inflammatory and vasoactive mediators. MC-related disorders are heterogeneous conditions characterized by the proliferation of MC within tissues and/or MC hyper-reactivity that leads to the uncontrolled release of mediators. MC disorders include mastocytosis, a clonal disease characterized by tissue MC proliferation, and MC activation syndromes that can be primary (clonal), secondary (related to allergic disorders), or idiopathic. Diagnosis of MC disorders is difficult because symptoms are transient, unpredictable, and unspecific, and because these conditions mimic many other diseases. Validation of markers of MC activation in vivo will be useful to allow faster diagnosis and better management of MC disorders. Tryptase, being the most specific MC product, is a widely used biomarker of proliferation and activation. Other mediators, such as histamine, cysteinyl leukotrienes, and prostaglandin D2, are unstable molecules and have limitations in their assays. Surface MC markers, detected by flow cytometry, are useful for the identification of neoplastic MC in mastocytosis but, so far, none of them has been validated as a biomarker of MC activation. Further studies are needed to identify useful biomarkers of MC activation in vivo.

Available and emerging therapies for bona fide advanced systemic mastocytosis and primary eosinophilic neoplasms

The historically poor prognosis of patients with advanced systemic mastocytosis (AdvSM) and primary eosinophilic neoplasms has shifted to increasingly favorable outcomes with the discovery of druggable targets. The multikinase/KIT inhibitor midostaurin and the highly selective KIT D816V inhibitor avapritinib can elicit marked improvements in measures of mast cell (MC) burden as well as reversion of MC-mediated organ damage (C-findings) and disease symptoms. With avapritinib, the achievement of molecular remission of KIT D816V and improved survival compared with historical therapy suggests a potential to affect disease natural history. BLU-263 and bezuclastinib are KIT D816V inhibitors currently being tested in trials of AdvSM. In the new World Health Organization and International Consensus Classifications, the category of "myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase (TK) gene fusions" is inclusive of rearrangements involving PDGFRA, PDGFRB, FGFR1, JAK2, FLT3, and ETV6::ABL1. While the successful outcomes with imatinib in FIP1L1::PDGFRA-positive cases and PDGFRB-rearranged neoplasms have become the "poster children" of these disorders, the responses of the other TK-driven neoplasms to small-molecule inhibitors are more variable. The selective FGFR inhibitor pemigatinib, approved in August 2022, is a promising therapy in aggressive FGFR1-driven diseases and highlights the role of such agents in bridging patients to allogeneic transplantation. This review summarizes the data for these approved and investigational agents and discusses open questions and future priorities regarding the management of these rare diseases.

Elevated Basal Serum Tryptase: Disease Distribution and Variability in a Regional Health System

BACKGROUND

Hereditary-alpha tryptasemia (HαT) is the most common etiology for elevated basal serum tryptase (BST). However, the utility of tryptase genotyping of individuals with elevated BST in general clinical practice remains undefined. Moreover, studies showing associations between elevated BST and chronic kidney disease (CKD), myelodysplastic syndrome (MDS), rheumatoid arthritis, or eosinophilic esophagitis did not include tryptase genotyping.

OBJECTIVE

To determine the utility of tryptase genotyping among individuals with moderate elevations in BST at a regional health system.

METHODS

Clinical and laboratory data from 109 subjects with basal tryptase values of 7.5 ng/mL or greater who were tested for HαT or had a disorder previously linked to elevated BST were collected retrospectively by chart review.

RESULTS

Fifty-eight subjects had elevated BST defined as 11.5 ng/mL or greater. HαT was found in 63.8% (n = 37), 12.1% (n = 7) had CKD, and 20.7% (n = 12) had clonal myeloid disorders. A total of 6.9% (n = 4) with elevated BST had negative testing for HαT, CKD, and myeloid neoplasms. Two subjects with CKD, 1 subject with MDS, and 1 with myeloid hypereosinophilic syndrome had negative testing for HαT. Among subjects with elevated BST and more than 1 tryptase measurement, 41.5% (n = 22) had BST variability that exceeded the 20% plus 2 formula. Increased BST variability was found in subjects with HαT, all forms of mastocytosis, CKD, MDS, and those with no associated diagnosis.

CONCLUSIONS

HαT, CKD, and clonal myeloid disorders or a combination of the 3 constitute approximately 90% of individuals with elevated BST in clinical practice. Myeloid neoplasms were over-represented in this cohort relative to population prevalence data suggesting tryptase measurement selection bias by clinicians or higher prevalence. Elevated BST is associated with increased tryptase variability, regardless of etiology.

Diagnosis and Management of Pediatric Hypereosinophilic Syndrome

Hypereosinophilic syndrome (HES) is a diverse group of disorders characterized by peripheral blood eosinophilia of 1.5 × 10⁹/L (1,500/μL) or greater with evidence of end-organ damage attributable to eosinophilia and no other cause of the end-organ damage. The HES is rare, especially in children. This review aims to provide best practices in diagnosis and treatment of HES in children, including how to differentiate between primary and secondary causes of hypereosinophilia; how to distinguish the differences in clinical presentation, treatment, and prognosis of HES in children and adults; and how to identify key steps in the evaluation and management of HES in children.

World Health Organization-defined eosinophilic disorders: 2022 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

The eosinophilias encompass a broad range of nonhematologic (secondary or reactive) and hematologic (primary or clonal) disorders with potential for end-organ damage.

DIAGNOSIS

Hypereosinophilia (HE) has generally been defined as a peripheral blood eosinophil count greater than 1.5 × 10⁹ /L. After exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ hybridization, next generation sequencing gene assays, and flow immunophenotyping to detect histopathologic or clonal evidence for an acute or chronic hematolymphoid neoplasm.

RISK STRATIFICATION

Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2016 World Health Organization endorses a semi-molecular classification scheme of disease subtypes. This includes the major category "myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2", and the myeloproliferative neoplasm subtype, "chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS). Lymphocyte-variant HE is an aberrant T-cell clone-driven reactive eosinophila, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion.

RISK-ADAPTED THERAPY

The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (eg, < 1.5 × 10⁹ /L) without symptoms or signs of organ involvement, a watch and wait approach with close follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Corticosteroids are first-line therapy for patients with lymphocyte-variant HE and HES. Hydroxyurea and interferon-α have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES. Mepolizumab, an interleukin-5 (IL-5) antagonist monoclonal antibody, was recently approved by the US Food and Drug Administration for patients with idiopathic HES. The use of the IL-5 receptor antibody benralizumab, as well as other targeted therapies such as JAK2 and FGFR1 inhibitors, is under active investigation.

Loeffler endocarditis with intracardiac thrombus: case report and literature review

Background

Loeffler endocarditis is a relatively rare and potentially life-threatening heart disease. This study aimed to identify the characteristic features of Loeffler endocarditis with intracardiac thrombus on a background of hypereosinophilic syndrome (HES).

Case presentation

We described a 57-year-old woman with Loeffler endocarditis and intracardiac thrombus initially presenting with neurological symptoms, who had an embolic stroke in the setting of HES. After cardiac magnetic resonance (CMR), corticosteroids and warfarin were administered to control eosinophilia and thrombi, respectively. During a 10-month follow-up, the patient performed relatively well, with no adverse events. We also systematically searched PubMed and Embase for cases of Loeffler endocarditis with intracardiac thrombus published until July 2021. A total of 32 studies were eligible and included in our analysis. Further, 36.4% of recruited patients developed thromboembolic complications, and the mortality rate was relatively high (27.3%). CMR was a powerful noninvasive modality in providing diagnostic and follow-up information in these patients. Steroids were administered in 81.8% of patients, achieving a rapid decrease in the eosinophil count. Also, 69.7% of patients were treated with anticoagulant therapy, and the thrombus was completely resolved in 42.4% of patients. Heart failure and patients not treated with anticoagulation were associated with poor outcomes.

Conclusions

Cardiac involvement in HES, especially Loeffler endocarditis with intracardiac thrombus, carries a pessimistic prognosis and significant mortality. Early steroids and anticoagulation therapy may be beneficial once a working diagnosis is established. Further studies are needed to provide evidence-based evidence for managing this uncommon manifestation of HES.

Case Report: Evolution of KIT D816V-Positive Systemic Mastocytosis to Myeloid Neoplasm With PDGFRA Rearrangement Responsive to Imatinib

Systemic mastocytosis (SM) is a rare neoplasm resulting from extracutaneous infiltration of clonal mast cells (MC). The clinical features of SM are very heterogenous and treatment should be highly individualized. Up to 40% of all SM cases can be associated with another hematological neoplasm, most frequently myeloproliferative neoplasms. Here, we present a patient with indolent SM who subsequently developed a myeloid neoplasm with PDGFRA rearrangement with complete response to low-dose imatinib. The 63-year-old patient presented with eosinophilia and elevated serum tryptase level. Bone marrow analysis revealed aberrant MCs in aggregates co-expressing CD2/CD25 and KIT D816V mutation (0.01%), and the FIP1L1-PDGFRA fusion gene was not identified. In the absence of ‘B’ and ‘C’ findings, we diagnosed an indolent form of SM. For 2 years after the diagnosis, the absolute eosinophil count progressively increased. Bone marrow evaluation showed myeloid hyperplasia and the FIP1L1-PDGFRA fusion gene was detected. Thus, the diagnosis of myeloid neoplasm with PDGFRA rearrangement was established. The patient was treated with imatinib 100 mg daily and rapidly obtained a complete molecular remission. The clinical, biological, and therapeutic aspects of SM might be challenging, especially when another associated hematological disease is diagnosed. Little is known about the underlying molecular and immunological mechanisms that can promote one entity prevailing over the other one. Currently, the preferred concept of SM pathogenesis is a multimutated neoplasm in which KIT mutations represent a “phenotype modifier” toward SM. Our patient showed an evolution from KIT mutated indolent SM to a myeloid neoplasm with PDGFRA rearrangement; when the eosinophilic component expanded, a regression of the MC counterpart was observed. In conclusion, extensive clinical monitoring associated with molecular testing is essential to better define these rare diseases and consequently their prognosis and treatment.

State-of-the-Art on Biomarkers for Anaphylaxis in Obstetrics

Anaphylaxis is an unpredictable systemic hypersensitivity reaction and constitutes a high risk of maternal and fetal morbidity and mortality when occurring during pregnancy. Currently, the acute management of anaphylaxis is based on clinical parameters. A total serum tryptase is only used to support an accurate diagnosis. There is a need to detect other biomarkers to further assess high-risk patients in obstetrics. Our objective is to present biomarkers in this complex interdisciplinary approach beyond obstetrician and anaesthetic management. Candidate biomarkers derive either from mediators involved in immunopathogenesis or upcoming molecules from systems biology and proteomics. Serum tryptase is determined by singleplex immunoassay method and is important in the evaluation of anaphylactic mast cell degranulation but also in the assessment of other risk factors for anaphylaxis such as systemic mastocytosis. Another category of biomarkers investigates the IgE-mediated sensitization to triggers potentially involved in the etiology of anaphylaxis in pregnant women, using singleplex or multiplex immunoassays. These in vitro tests with natural extracts from foods, venoms, latex or drugs, as well as with molecular allergen components, are useful because in vivo allergy tests cannot be performed on pregnant women in such a major medical emergency due to their additional potential risk of anaphylaxis.

The causes of a peripheral blood eosinophilia in a secondary care setting

BACKGROUND

A peripheral blood eosinophilia of greater than 1.0 × 10⁹ /L is relatively unusual and offers a clue to the underlying diagnosis. In 2003, we established a specialist service to diagnose unexplained eosinophilia.

OBJECTIVE

To describe the causes of an eosinophilia in our service and the diagnostic algorithm we developed.

METHODS

Subjects were referred by physician colleagues across a range of specialties and undertook standard investigations following a semi-structured protocol. Data were extracted from a bespoke database.

RESULTS

Three hundred and eighty two subjects were referred over a 17-year period. Average age was 54 years and 183 (48%) of subjects were female, with 21 of 25 (84%) females in the idiopathic eosinophilic pneumonia group (p < 0001), 22 of 30 (73%) females in the gastrointestinal disease group (p < .008), but 11 of 37 (30%) females in the eosinophilic granulomatosis with polyangiitis group (p < .04). A diagnosis was assigned after systematic evaluation using a pre-defined algorithm in 361 (94.5%) of cases. Fungal allergy (82 subjects: 21%), parasitic infection (61 subjects: 16%) and severe eosinophilic asthma (50 subjects: 13%) were the three commonest individual diagnoses. Hypereosinophilic syndrome (HES) disease including eosinophilic granulomatosis with polyangiitis (EGPA) accounted for 85 subjects (20%) of which seven subjects (2%) had myeloproliferative disease (M-HES). A high IgE was common, and 79 (91%) of subjects with complete data who had an IgE of ≥1000 IU/L had fungal allergy or parasite infection. The serum tryptase was raised in 44 of 302 (14.5%) of individuals across all diagnostic groups, though none had mastocytosis.

CONCLUSION

A diagnosis of an unexplained eosinophilia can usually be determined using as semi-structured algorithm. Parasitic infection and fungal allergy often with severe eosinophilic asthma were common causes, whereas HES, particularly myeloproliferative, disease was relatively rare.

Systemic mastocytosis in adults: 2021 Update on diagnosis, risk stratification and management

OVERVIEW

Systemic mastocytosis (SM) results from a clonal proliferation of abnormal mast cells (MC) in extra-cutaneous organs.

DIAGNOSIS

The major criterion is presence of multifocal clusters of spindled MC in the bone marrow. Minor diagnostic criteria include elevated serum tryptase level, abnormal MC CD25 expression, and presence of KITD816V mutation.

RISK STRATIFICATION

Establishing SM subtype as per the World Health Organization classification system is an important first step. Broadly, patients either have indolent/smoldering SM (ISM/SSM) or advanced SM, the latter includes aggressive SM (ASM), SM with associated hematological neoplasm (SM-AHN), and mast cell leukemia (MCL). Identification of poor-risk mutations (ie, ASXL1, RUNX1, SRSF2, NRAS) further refines the risk stratification. Recently, clinical and hybrid clinical-molecular risk models have been developed to more accurately assign prognosis in SM patients.

MANAGEMENT

Treatment goals for ISM patients are primarily directed towards anaphylaxis prevention/symptom control/osteoporosis treatment. Patients with advanced SM frequently need MC cytoreductive therapy to ameliorate disease-related organ dysfunction. High response rates have been seen with small-molecule inhibitors that target mutant-KIT, including midostaurin (Food and Drug Administration approved) or avapritinib (investigational). Other options for MC cytoreduction include cladribine or interferon-α, although head-to-head comparisons are lacking. Treatment of SM-AHN primarily targets the AHN component, particularly if an aggressive disease such as acute myeloid leukemia is present. Allogeneic stem cell transplant can be considered in such patients, or in those with relapsed/refractory advanced SM. Imatinib has a limited therapeutic role in SM; effective cytoreduction is limited to those with imatinib-sensitive KIT mutations.

The Genetic Basis and Clinical Impact of Hereditary Alpha-Tryptasemia

Hereditary alpha-tryptasemia (HαT) is an autosomal dominant genetic trait found in 4% to 6% of the general population and defined by excess copies of alpha-tryptase at TPSAB1. Elevated basal serum tryptase (sBT >8 ng/mL) is a defining feature of HαT and appears to result from increased pro-alpha-tryptase synthesis and secretion rather than mast cell activation. It is estimated that approximately one-third of individuals with HαT have associated symptoms, including cutaneous, gastrointestinal, atopic, musculoskeletal, autonomic, and neuropsychiatric manifestations. HαT is found at a disproportionately high rate in systemic mastocytosis and idiopathic anaphylaxis, and is a modifying factor that independently increases the incidence and severity of anaphylaxis. The varied phenotypes associated with HαT may, in part, result from coinheritance of other genetic variants, increased expression of α-/ß-tryptase heterotetramers, and/or overexpression of pro-alpha-tryptase, although further studies are needed. There is an accurate diagnostic test available to confirm HαT in patients that can be used in combination with sBT to help risk-stratify individuals in whom bone marrow biopsy is being considered. There is no specific treatment for symptoms associated with HαT, and management is focused on controlling clinical manifestations with mast cell mediator antagonists, aspirin, inhalers, epinephrine, omalizumab, and involvement of other specialists.

The Role of Bone Marrow Evaluation in Clinical Allergy and Immunology Practice: When and Why

Allergists and immunologists rely on other specialists for higher risk procedures such as biopsies of the lung or gastrointestinal tract. However, we perform and interpret a handful of procedures ourselves. Training programs have historically required competency for prescribing immunoglobulin infusions, patch testing, rhino laryngoscopy, lung function testing, and provocation testing for airway hyperreactivity even though other specialists often perform them. Bone marrow aspirations and biopsies are not included in fellowship training assessments despite a significant number of marrow evaluations being requested by allergists and immunologists. For example, nearly 1 marrow assessment per month has been requested over 2 years for patients in the Allergy Immunology Clinic at Walter Reed National Military Medical Center. Marrow assessments are often required for diagnosis, monitoring, and treatment-related toxicities. Interpretive and procedural competency would benefit the field given the range of diseases in clinical immunology practice that require marrow assessment. We have generated a comprehensive list of the major conditions that might require bone marrow assessments in any Allergy and Immunology practice. We then summarize the specific tests that must be ordered and show how to determine sample quality. Finally, some providers may desire procedural competency and for those individuals we discuss tips for the procedure.

Epidemiology, clinical picture and long-term outcomes of FIP1L1-PDGFRA-positive myeloid neoplasm with eosinophilia: Data from 151 patients

FIP1L1-PDGFRA-positive myeloid neoplasm with eosinophilia (F/P+ MN-eo) is a rare disease: robust epidemiological data are lacking and reported issues are scarce, of low sample-size and limited follow-up. Imatinib mesylate (IM) is highly efficient but no predictive factor of relapse after discontinuation has yet been identified. One hundred and fifty-one patients with F/P+ MN-eo (143 males; mean age at diagnosis 49 years; mean annual incidence: 0.18 case per million population) were included in this retrospective nationwide study involving all French laboratories who perform the search of F/P fusion gene (study period: 2003-2019). The main organs involved included the spleen (44%), skin (32%), lungs (30%), heart (19%) and central nervous system (9%). Serum vitamin B12 and tryptase levels were elevated in 74/79 (94%) and 45/57 (79%) patients, respectively, and none of the 31 patients initially treated with corticosteroids achieved complete hematologic remission. All 148 (98%) IM-treated patients achieved complete hematologic and molecular (when tested, n = 84) responses. Forty-six patients eventually discontinued IM, among whom 20 (57%) relapsed. In multivariate analysis, time to IM initiation (continuous HR: 1,01 [0.99-1,03]; P = .05) and duration of IM treatment (continuous HR: 0,97 [0,95-0,99]; P = .004) were independent factors of relapse after discontinuation of IM. After a mean follow-up of 80 (56) months, the 1, 5- and 10-year overall survival rates in IM-treated patients were 99%, 95% and 84% respectively. In F/P+ MN-eo, prompt initiation of IM and longer treatment durations may prevent relapses after discontinuation of IM.

Doctor, I Think I Am Suffering from MCAS: Differential Diagnosis and Separating Facts from Fiction

Mast cell activation syndrome (MCAS) is a rare condition defined by a severe systemic reaction to mast cell (MC)-derived mediators. Most cases present with clinical signs of anaphylaxis, and some have an underlying IgE-dependent allergy. A primary MC disease (mastocytosis) may also be detected. Severe recurrent MCAS episodes requiring intensive care or even resuscitation are typically found in patients who suffer from both mastocytosis and allergy against certain triggers, such as hymenoptera venom components. A less severe form and a local form of MC activation (MCA) also exist. For these patients, diagnostic criteria are lacking. Moreover, a number of different, unrelated, conditions with overlapping symptoms may be confused with MCAS. As a result, many patients believe that they are suffering from MCAS but have in fact a less severe form of MCA or another underlying disease. In the current article, we review the potential differential diagnoses of MCA and MCAS and discuss available diagnostic criteria and diagnostic tools. These criteria and assays may be useful in daily practice and help avoid unnecessary referrals and unjustified fears in patients.

[Tryptase: A practical guide for the physician]

Tryptase is the most abundant endopeptidase released by mast cells degranulation, involved in many pro and anti-inflammatory processes. Normal serum tryptase range is 0-11.4 μg/L. Tryptase is a useful diagnostic tool for anaphylaxis, systemic mastocytosis (SM) and mast cell activation syndrome (MCAS), where specific threshold values must be used. SM diagnosis criteria include evidence of dense mast cell infiltrate either in the bone marrow or the affected organ (such as skin), presence of KIT D816V mutation and elevated serum tryptase level (>20 μg/L). In SM, tryptase level is correlated with the burden of mast cells in bone marrow. MCAS should be considered in case of severe and recurrent typical clinical signs of systemic mast cell activation involving at least two organs, associated with an increase in serum tryptase level of 20% + 2 μg/L from the individual's baseline. Anaphylaxis is the most severe among hypersensitivity reactions. A clonal mast cell disorder is a central question in anaphylaxis and appropriate explorations should be conducted in these patients. Triggers for anaphylactic reactions vary significantly in the general population and in patients with MS or MCAS. Finally, physicians must be aware of the many pathological and physiological situations that affect tryptase levels.

Loeffler's Endocarditis and Hypereosinophilic Syndrome

Loeffler's endocarditis and hypereosinophilic syndromes are a unique group of infiltrative disorders characterized by hypereosinophilia, inflammatory thrombotic, and ultimately, fibrotic involvement of the heart leading to multiple complications including valve involvement, thromboembolic phenomena, heart failure. Clinical recognition, comprehensive laboratory and multimodality imaging diagnostic workup, and early initiation of treatment have been shown to slow down the progression and promote remission. This review addresses a detailed analysis of Loeffler's endocarditis and hypereosinophilic syndromes.

Cough in hypereosinophilic syndrome: case report and literature review

BACKGROUND

Cough and airway eosinophilic inflammation has not been highlighted in hypereosinophilic syndrome (HES).

CASE PRESENTATION

We report 2 further cases and reviewed the clinical features and treatment of HES present with cough from the literature. Both cases were middle age male, presenting with chronic cough, airway eosinophilic inflammation and hyper eosinophilia who have been previous misdiagnosed as cough-variant asthma and failed anti-asthma treatment. PDGFRA fusion gene was confirmed in one case, but not in the other case. Both had evidence of myeloproliferative features. The tyrosine kinase inhibitor, imatinib, resulted in complete resolution of eosinophilia and cough. By searching PubMed, we found 8 HES cohorts of 411 cases between 1975 and 2013, where the incidence of cough was 23.11%. Sixteen case reports of HES presented with cough as predominant or sole symptom, with nine male patients with positive PDGFRA fusion gene, who responded well to imatinib. Six of seven patients, who tested negative for the PDGFRA, responded to systemic glucocorticoids.

CONCLUSIONS

Cough and airway eosinophilic inflammation is common in some HES patients. PDGFRA+ HES patients present with chronic cough respond well to imatinib. Our case reports indicate that PDGFRA negative HES patients may respond to imatinib as well.

Elevated Serum Tryptase in Non-Anaphylaxis Cases: A Concise Review

One of the most important blood tests in the field of allergy, mast cell tryptase has numerous diagnostic uses, particularly for anaphylactic reactions and for the diagnosis of mastocytosis. However, there are numerous other non-anaphylactic conditions where clinicians may see elevated serum tryptase (hypertryptasemia) and the practicing clinician ought to be aware of these important differential diagnoses. Such conditions include systemic mastocytosis, hematological malignancies, and chronic kidney disease. This article provides a comprehensive, updated summary on the variety of non-anaphylactic conditions where hypertryptasemia may be seen.

Gastrointestinal Manifestations of Hypereosinophilic Syndromes and Mast Cell Disorders: a Comprehensive Review

Hypereosinophilic syndrome and mastocytosis are relatively rare proliferative diseases encountered in the general population. However, allergists frequently consider these disorders in the differential of patients presenting with gastrointestinal, pulmonary, cutaneous, and allergic symptoms. Gastrointestinal symptoms are some of the most frequent and/or debilitating aspects of both disease states and in many cases lead to poor quality of life and functional limitation for the patient. They are the third most common clinical manifestation in hypereosinophilic syndrome and have been found to be the most distressful aspect of the disorder in those with systemic mastocytosis. Both eosinophils and mast cells play integral parts in normal gut physiology, but when and how exactly their effector functionality translates into clinically significant disease remains unclear, and the available literature regarding their pathophysiology remains sparse. Eosinophils and mast cells even, in fact, may not necessarily function in isolation from each other but can participate in bidirectional crosstalk. Both are affected by similar mediators and can also influence one another in a paracrine fashion. Their interactions include both production of soluble mediators for specific eosinophil and mast cell receptors (for example, eosinophil recruitment and activation by mast cells releasing histamine and eotaxin) as well as direct physical contact. The mechanistic relationship between clonal forms of hypereosinophilia and systemic mastocytosis has also been explored. The nature of gastrointestinal symptomatology in the setting of both hypereosinophilic syndrome and mast cell disease is frequently manifold, heterogeneous, and the lack of better targeted therapy makes diagnosis and management challenging, especially when faced with a substantial differential. Currently, the management of these gastrointestinal symptoms relies on the treatment of the overall disease process. In hypereosinophilia patients, systemic corticosteroids are mainstay, although steroid-sparing agents such as hydroxyurea, IFN-α, methotrexate, cyclosporine, imatinib, and mepolizumab have been utilized with varying success. In mastocytosis patients, anti-mediator therapy with antihistamines and mast cell stabilization with cromolyn sodium can be considered treatments of choice, followed by other therapies yet to be thoroughly studied, including the role of the low-histamine diet, corticosteroids, and treatment of associated IBS symptoms. Given that both eosinophils and mast cells may have joint pathophysiologic roles, they have the potential to be a combined target for therapeutic intervention in disease states exhibiting eosinophil or mast cell involvement.

Ascites in a young male: idiopathic FIP1L1-PDGFRA-negative hypereosinophilic syndrome

Introduction

Idiopathic hypereosinophilic syndrome is defined as persistently elevated peripheral blood absolute eosinophil count of more than 1.5 × 109/L for at least six months with no obvious secondary cause.

Case Presentation

We report the case of a 26-year-old gentleman of Malay ethnicity who presented to the medical department with a three-week history of abdominal distension associated with dyspepsia and epigastric pain. Physical examination revealed ascites. The complete blood count portrayed peripheral leucocytosis with eosinophilia of 8.84 × 109/L. Parasitic serology was negative. Paracentesis analysis showed exudative ascites with an absolute eosinophil count of 8 × 109/L. He was referred to the haematology department. He was noticed to have bilateral tonsillitis and pruritic skin rash at the legs. There were no palpable lymph nodes or organomegaly. A peripheral blood film showed 44% eosinophils with no excess blasts. Clonal eosinophilic fusion studies did not detect FIP1L1-PDGFRA mutation. JAK2 V617F and BCR-ABL1 mutations were undetected. Serum B12 and tryptase levels were normal. A whole-body computed tomography imaging showed bowel wall thickening at the duodenum, jejunum, ileum, rectosigmoid and splenic flexure. Sections of fragments taken from the endoscopy showed features of eosinophilic gastritis and colitis on histology. Bone marrow biopsy depicted marked eosinophilia. He was started on oral imatinib mesylate 200 mg daily and oral prednisolone 0.5 mg/kg daily which was tapered based on response. He achieved complete remission and is now asymptomatic.

Conclusion

The diagnosis of hypereosinophilic syndrome should be considered in a patient with unexplained ascites. Secondary sinister causes such as malignancy should always be excluded.

Contributions of Eosinophils to Human Health and Disease

The human eosinophil has long been thought to favorably influence innate mucosal immunity but at times has also been incriminated in disease pathophysiology. Research into eosinophil biology has uncovered a number of interesting contributions by eosinophils to health and disease. However, it appears that not all eosinophils from all species are created equal. It remains unclear, for example, exactly how having eosinophils benefits the human host when helminth infections in the developed world have become scarce. This review focuses on our current state of knowledge as it relates to human eosinophils. When information is lacking, we discuss lessons learned from mouse studies that may or may not directly apply to human biology and disease. It is an exciting time to be an "eosinophilosopher" because the use of biologic agents that selectively target eosinophils provides an unprecedented opportunity to define the contribution of this cell to eosinophil-associated human diseases.

Mast cell activation in the context of elevated basal serum tryptase: genetics and presentations

PURPOSE OF REVIEW

To describe inherited and acquired genetic variants and clinical entities associated with increased basal serum tryptase (BST), distinguish these levels from those which acutely rise due to mast cell activation, and finally to characterize the association between chronically elevated basal serum tryptase and episodic mast cell activation.

RECENT FINDINGS

Hereditary alpha-tryptasemia is a commonly inherited genetic cause for basally elevated serum tryptase and explains elevated BST in many individuals who do not have evidence of clonal myeloid or mast cell disease. When clonal myeloid disease is present, BST may be elevated and can be a biomarker of a number of disparate disorders of the myeloid compartment. Elevated BST is most commonly caused by hereditary alpha tryptasemia but may also be indicative of clonal myeloid disease. Clinical reports suggest that elevated BST is associated with increased risk for more severe systemic allergic reactions to a number of eliciting agents and exposures. Additional studies are needed to determine the role that inherited or acquired genetic variants associated with elevated BST and clonal or non-clonal myeloid diseases may play in these reactions.

Refractory Anaphylaxis: Data From the European Anaphylaxis Registry

Refractory anaphylaxis (unresponsive to treatment with at least two doses of minimum 300 μg adrenaline) is a rare and often fatal hypersensitivity reaction. Comprehensive data on its definition, prevalence, and risk factors are missing. Using the data from the European Anaphylaxis Registry (11,596 cases in total) we identified refractory anaphylaxis cases (n = 42) and analyzed these in comparison to a control group of severe anaphylaxis cases (n = 4,820). The data show that drugs more frequently elicited refractory anaphylaxis (50% of cases, p < 0.0001) compared to other severe anaphylaxis cases (19.7%). Cases elicited by insects (n = 8) were more often due to bees than wasps in refractory cases (62.5 vs. 19.4%, p = 0.009). The refractory cases occurred mostly in a perioperative setting (45.2 vs. 9.05, p < 0.0001). Intramuscular adrenaline (as a first line therapy) was administered in 16.7% of refractory cases, whereas in 83.3% of cases it was applied intravenously (significantly more often than in severe anaphylaxis cases: 12.3%, p < 0.0001). Second line treatment options (e.g., vasopression with dopamine, methylene blue, glucagon) were not used at all for the treatment of refractory cases. The mortality rate in refractory anaphylaxis was significantly higher (26.2%) than in severe cases (0.353%, p < 0.0001). Refractory anaphylaxis is associated with drug-induced anaphylaxis in particular if allergens are given intravenously. Although physicians frequently use adrenaline in cases of perioperative anaphylaxis, not all patients are responding to treatment. Whether a delay in recognition of anaphylaxis is responsible for the refractory case or whether these cases are due to an overflow with mast cell activating substances—requires further studies. Reasons for the low use of second-line medication (i.e., methylene blue or dopamine) in refractory cases are unknown, but their use might improve the outcome of severe refractory anaphylaxis cases.

World Health Organization-defined eosinophilic disorders: 2019 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

The eosinophilias encompass a broad range of non-hematologic (secondary or reactive) and hematologic (primary, clonal) disorders with potential for end-organ damage.

DIAGNOSIS

Hypereosinophilia has generally been defined as a peripheral blood eosinophil count greater than 1.5 × 10⁹ /L, and may be associated with tissue damage. After exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on a combination of various tests. They include morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ-hybridization, flow immunophenotyping, and T-cell clonality assessment to detect histopathologic or clonal evidence for an acute or chronic hematolymphoid neoplasm.

RISK STRATIFICATION

Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2016 World Health Organization endorses a semi-molecular classification scheme of disease subtypes. This includes the major category "myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2", and the MPN subtype, "chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS). Lymphocyte-variant hypereosinophilia is an aberrant T-cell clone-driven reactive eosinophila, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion.

RISK-ADAPTED THERAPY

The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (eg, <1.5 × 10⁹ /L) without symptoms or signs of organ involvement, a watch and wait approach with close-follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Corticosteroids are first-line therapy for patients with lymphocyte-variant hypereosinophilia and HES. Hydroxyurea and interferon-alfa have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES. In addition to hydroxyurea, second line cytotoxic chemotherapy agents, and hematopoietic stem cell transplantation have been used for aggressive forms of HES and CEL, with outcomes reported for limited numbers of patients. The use of antibodies against interleukin-5 (IL-5) (mepolizumab), the IL-5 receptor (benralizumab), as well as other targets on eosinophils remains an active area of investigation.

Eosinophilic disorders: evaluation of current classification and diagnostic criteria, proposal of a practical diagnostic algorithm

Eosinophilic disorders represent a group of pathologic conditions with highly heterogeneous pathophysiology and clinical presentation and variable prognosis, ranging from asymptomatic or mild, to severe and complex cases, with fatal outcome. Interest in this group of disorders has increased during the last two decades, with consistent progress made regarding understanding of molecular mechanisms, refining of diagnostic criteria, classification and evaluation of therapeutic options. There are still many gaps and difficulties in evaluating eosinophilic syndromes and diseases in medical practice. The disease prognosis depends mainly on the cause and mechanism of eosinophilia, on severity of organ dysfunction and on accurate diagnosis and response to treatment. Besides primary hypereosinophilic syndromes and secondary (reactive) eosinophilias, many associated or idiopathic forms have been described, making this topic a complex and difficult medical entity. An important aim of the experts in the field is to agree upon a more clear and practically useful classification, a better characterization of various phenotypes and endotypes of eosinophilic diseases and to identify novel biomarkers and more effective therapies. The aim of this paper is to review recent data from the literature regarding definition, classification and diagnosis criteria of eosinophilic diseases and to propose a revised and updated diagnostic algorithm useful in clinical practice.

Efficacy of Imatinib Mesylate in a Patient with Idiopathic Hypereosinophilic Syndrome and Severe Heart Involvement

Idiopathic hypereosinophilic syndrome (HES) is a rare, chronic hematological disease mainly characterized by unexplained prolonged eosinophilia, with frequent evidence of secondary organ damage. Treatment with steroids, chemotherapy, interferon-alpha (IFN-α), or imatinib-mesylate may improve the prognosis.

Here we describe the case of a young male patient with a six-year history of HES and severe heart involvement who, after unsuccessful treatment attempts with steroids, hydroxyurea and IFN-α, had a prompt, clinical and hematological complete remission following administration of imatinib. As his cardiac function also markedly improved, he was considered for heart transplant. However, seven years after the onset of the disease and four months after the termination of imatinib treatment the patient died of a cerebral hemorrhage that occurred during an episode of acute respiratory sepsis. Imatinib has been previously reported to be effective in some hematological conditions with no evidence of the BCR/ABL transcript. The mechanisms that are probably involved in the response to imatinib in HES are also discussed.

Pediatric Hypereosinophilia: Characteristics, Clinical Manifestations, and Diagnoses

BACKGROUND

Eosinophilia is associated with various conditions, including allergic, infectious, and neoplastic disorders. The diagnostic differential is broad, and data on hypereosinophilia in pediatric patients are limited.

OBJECTIVE

The objectives of this study were to identify cases of hypereosinophilia in a tertiary pediatric medical center, determine clinical characteristics and disease associations, and estimate the incidence of hypereosinophilia in the hospital and geographic populations.

METHODS

A retrospective chart review included patients younger than 18 years presenting to a tertiary pediatric medical center (January 1, 2008, to May 31, 2017) with absolute eosinophil counts (AECs) greater than or equal to 1.50 thousand eosinophils/microliter (K/μL) recorded on at least 2 occasions at least 4 weeks apart (N = 176). Clinical characteristics, laboratory values, treatment course, and associated diagnoses were evaluated.

RESULTS

The most common cause of hypereosinophilia in this cohort was secondary hypereosinophilia. Atopic dermatitis, graft-versus-host disease, sickle cell disease, and parasitic infections were the most common conditions associated with hypereosinophilia. Median age at diagnosis was 4.6 (interquartile range, 1.5-10.5) years. Median peak AEC was 3.16 (2.46-4.78) K/μL. Hypereosinophilia occurred most frequently in patients aged between 6 and 11 years (24.4%) and younger than 1 year (18.2%). Patients with neoplasms and immune deficiencies had significantly higher peak AECs than did patients with overlap hypereosinophilic syndrome and atopic diseases (P < .0001).

CONCLUSIONS

Pediatric hypereosinophilia has an incidence of 54.4 per 100,000 persons per year, with children younger than 1 year and aged 6 to 11 years accounting for most affected patients. Pediatric hypereosinophilia is not uncommon and remains underrecognized, highlighting a need for clinicians to identify patients who meet criteria for hypereosinophilia and to pursue a thorough evaluation.

Eosinophilia in acute myeloid leukemia: Overlooked and underexamined

The presence of eosinophilia in acute myeloid leukemia (AML) suggests an underlying core binding factor (CBF) lesion, a platelet derived growth factor (PDGFR) translocation, or another rare translocation (such as ETV6-ABL1). Each of these cytogenetic entities carries unique diagnostic, prognostic, and therapeutic implications. CBF AML is most common and as such, its treatment is more clearly established, consisting of intensive induction chemotherapy followed by cytarabine based consolidation. Due in large part to its intrinsic chemo-sensitivity, CBF AML is associated with relatively high rates of remission and survival. PDGFR mediated AML is comparatively rare, and as such, diagnostic and treatment paradigms are not as well defined. Early identification of PDGFR translocations is essential, as they confer profound imatinib sensitivity which may, in many instances, spare the need for chemotherapy. Prompt recognition of such lesions requires a strong index of suspicion, and as such these diagnoses are often initially overlooked. Unfortunately, many cases of PDGFR associated AML, particularly those with other concurrent cytogenetic abnormalities, demonstrate treatment emergent imatinib resistance. Such patients continue to present a challenge, even with the advent of novel tyrosine kinase inhibitors (TKIs). Patients with rare translocations such as ETV6-ABL1 are not well described however seem to follow an aggressive clinical course, with limited response to imatinib, and poor outcomes. This review examines the significance of eosinophilia in the context of AML, with respect to its presentation, pathology, and cytogenetics, and with special attention to appropriate evaluation and treatment.

Idiopathic hypereosinophilic syndrome with cutaneous involvement: a comparative review of 32 cases

Although idiopathic hypereosinophilic syndrome (HES) is uncommon, we studied the clinical characteristics of this disorder in patients with cutaneous involvement. We chronicle the case of a patient with diffuse skin rash due to idiopathic HES from our clinical experience. Furthermore, a systematic literature search of the medical databases PubMed and Google Scholar was conducted. A total of 32 cases fulfilled the inclusion criteria. The data on patients' characteristics, epidemiology, clinical features, diagnosis, treatment and outcome were collected and analysed. This review illustrates that physicians should maintain a high index of clinical suspicion for idiopathic HES in patients presenting with dermatological lesions and hypereosinophilia, without an obvious cause. Randomised clinical trials are warranted to outline a generalised and efficient therapeutic approach in these patients. Additionally, this paper highlights the need for population-based studies to delineate the magnitude and scope of this association.

The new tool "KIT" in advanced systemic mastocytosis

Mastocytosis is a rare disease characterized by KIT-driven expansion and accumulation of neoplastic mast cells in various tissues. Although mediator symptoms related to mast cell activation can impose a symptom burden in cutaneous disease and across the spectrum of systemic mastocytosis subtypes, the presence of an associated hematologic neoplasm and/or organ damage denotes advanced disease and the potential for increased morbidity and mortality. In addition to the revised 2016 World Health Organization classification of mastocytosis, a new diagnostic and treatment toolkit, tethered to enhanced molecular characterization and monitoring, is poised to transform the management of patients with advanced systemic mastocytosis (advSM). Although the efficacy of midostaurin and novel selective KIT D816V inhibitors, such as avapritinib (BLU-285), have validated KIT as a therapeutic target, the clinical and biologic heterogeneity of advSM requires that we reimagine the blueprint for tackling these diseases and use tools that move beyond KIT-centric approaches.

Mast cells and mast cell tryptase enhance migration of human lung fibroblasts through protease-activated receptor 2

BACKGROUND

Mast cells may activate fibroblasts and contribute to remodeling processes in the lung. However, the mechanism behind these actions needs to be further investigated. Fibroblasts are major regulators of on-going remodeling processes. Protease activated receptor 2 (PAR2) expressed by fibroblasts may be activated by serine proteases, such as the mast cell mediator tryptase. The objective in this study was to investigate the effects of mast cells and specifically mast cell tryptase on fibroblast migration and the role of PAR2 activation.

METHODS

Human lung fibroblasts (HFL-1) were cultured together with human peripheral blood-derived mast cells or LAD2 mast cells and stimulated with either conditioned medium from LAD2 cells or tryptase. Analyses of immunological stimulation of mast cells by IgE/anti IgE in the co-culture system were also performed. The importance of PAR2 activation by mast cells and mast cell tryptase for the migratory effects of fibroblasts was investigated by pre-treatment with the PAR2 antagonist P2pal-18S. The expression of PAR2 was analyzed on fibroblasts and mast cells.

RESULTS

The migratory capacity of HFL-1 cells was enhanced by blood-derived mast cells (p < 0.02), LAD2 cells (p < 0.001), conditioned medium (p < 0.05) and tryptase (p < 0.006). P2pal-18S decreased the induced migration caused by mast cells (p < 0.001) and tryptase (p < 0.001) and the expression of PAR2 was verified in HFL-1 cells. Mast cells immunologically stimulated with IgE/Anti IgE had no further effects on fibroblast migration.

CONCLUSIONS

Mast cells and the mast cell mediator tryptase may have crucial roles in inducing lung fibroblast migration via PAR-2 activation, which may contribute to remodeling processes in chronic lung diseases.

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.

Potential involvement of neutrophils in human thyroid cancer

Background

Neutrophil functions have long been regarded as limited to acute inflammation and the defense against microbes. The role(s) of neutrophils in cancer remain poorly understood. Neutrophils infiltrate tumors and are key effector cells in the orchestration of inflammatory responses. Thyroid cancer (TC) is the most recurrent endocrine malignant tumor and is responsible for 70% of deaths due to endocrine cancers. No studies are so far available on the role of neutrophils in TC.

Objective

Our purpose was to study the involvement of tumor-associated neutrophils in TC.

Methods

Highly purified human neutrophils (>99%) from healthy donors were stimulated in vitro with conditioned media derived from TC cell lines TPC1 and 8505c (TC-CMs). Neutrophil functions (e.g., chemotaxis, activation, plasticity, survival, gene expression, and protein release) were evaluated.

Results

TC-derived soluble factors promoted neutrophil chemotaxis and survival. Neutrophil chemotaxis toward a TC-CM was mediated, at least in part, by CXCL8/IL-8, and survival was mediated by granulocyte-macrophage colony-stimulating factor (GM-CSF). In addition, each TC-CM induced morphological changes and activation of neutrophils (e.g., CD11b and CD66b upregulation and CD62L shedding) and modified neutrophils’ kinetic properties. Furthermore, each TC-CM induced production of reactive oxygen species, expression of proinflammatory and angiogenic mediators (CXCL8/IL-8, VEGF-A, and TNF-α), and a release of matrix metalloproteinase 9 (MMP-9). Moreover, in TC patients, tumor-associated neutrophils correlated with larger tumor size.

Conclusions

TC cell lines produce soluble factors able to “educate” neutrophils toward an activated functional state. These data will advance the understanding of the molecular and cellular mechanisms of innate immunity in TC.

A young female presenting with heart failure secondary to eosinophilic myocarditis: a case report and review of the literature

Background

Eosinophilic myocarditis is one of the fatal complications of idiopathic hypereosinophilic syndromes. Given the rarity of this form of myocarditis, it is often under-recognized. We describe a young girl who presented with features of heart failure. To our knowledge, this is the first reported case of eosinophilic myocarditis in a young Sri Lankan female.

Case presentation

A previously healthy 21 year old Sri Lankan female admitted with shortness of breath for 1 week duration with associated low grade fever and profuse sweating. She was mildly febrile and dyspnoeic with absent ankle oedema. She was tachycardic and had elevated Jugular venous pressure with negative Kussmaul sign. Blood pressure was 100/70 mmHg. Clinically there was no cardiomegaly and heart sounds were slightly muffled with gallop rhythm. Bilateral basal fine end inspiratory crackles and mild hepatosplenomegaly were noted. The laboratory examinations showed leucocytosis with severe eosinophilia with no abnormal cells. Her ESR, Troponin I and Brain natriuretic peptide were elevated with normal CRP and electrocardiogram showed sinus tachycardia with wide spread ST depression. Heart failure was evident on chest X-ray and 2D-echocardiogram showed global left ventricular hypokinesia with 40% ejection fraction and a thin layer of pericardial effusion. Mild hepatosplenomegaly without lymphadenopathy was detected in the ultrasound scan. Bone marrow biopsy showed hypereosinophilia with no evidence of bone marrow infiltration. FIP1L1–PDGFRA fusion transcript and BCR–ABL transcript were not detected. Secondary causes for hypereosinophilia were excluded and the diagnosis of idiopathic hypereosinophilic syndrome and eosinophilic myocarditis was made. She had good response to steroids clinically and biochemically with complete recovery of left ventricular function. She is now on steroid to be continued at least 6 months to 1 year.

Conclusion

Eosinophilic myocarditis is a rare but fatal disease if left untreated. Hence clinicians should have high index of suspicion to diagnose eosinophilic myocarditis in clinical context of heart failure due to myocarditis. The diagnoses of eosinophilic myocarditis may often be challenged especially in a poor recourse setting. However available investigation should be used to diagnose this condition without delay. Early treatment with systemic steroids may prevent fatal outcome and therapies for this disease have yet to be validated in large prospective studies.

Loeffler endocarditis as a rare cause of heart failure with preserved ejection fraction: A case report and review of literature

RATIONALE

Hypereosinophilic syndrome (HES) is a rare disease characterized by hypereosinophilia and its ensuing organ damage. Cardiac involvement is divided into 3 chronological stages: an acute necrotic stage; a thrombus formation stage; and a fibrotic stage. Infiltration of the myocardium by eosinophilic cells followed by endomyocardial fibrosis is known as "Loeffler endocarditis."

PATIENT CONCERNS

We report a case of a 60-year-old man diagnosed with left-sided restrictive cardiomyopathy.

DIAGNOSIS

The patient experienced heart failure with preserved ejection fraction. The cardiac MRI showed intense, linear, delayed gadolinium enhancement of the endocardium of the lateral wall of the left ventricle, and obliteration of the LV apex. He was ultimately identified as Loeffler endocarditis.

INTERVENTION

A bone marrow smear and biopsy revealed the FIP1L1-PDGFRA fusion gene was positive in 82% of segmented nucleated cells.

OUTCOME

Our patient responded well to prednisone at 1 mg/kg/d.

LESSONS

HES is a rare disease that often afflicts the heart. Cardiac involvement in hypereosinophilia, especially Loeffler endocarditis, carries a poor prognosis and significant mortality. Early detection and treatment of the disease is therefore essential. Further studies are needed to ascertain therapeutic corticosteroid dosages and develop targeted gene therapies, both important steps to ameliorate the effects of Loeffler endocarditis and improve patient outcomes.

Hypereosinophilic Syndrome Subtype Predicts Responsiveness to Glucocorticoids

BACKGROUND

Glucocorticoids (GCs) are considered first-line treatment for platelet-derived growth factor α (PDGFRA)-negative hypereosinophilic syndromes (HESs). Despite this, little is known about clinical predictors of GC responsiveness in HES.

OBJECTIVE

Knowledge of clinical and laboratory predictors of GC response before initiation of GC could lead to more rational selection of subjects with HES for whom earlier institution of second-line and alternative therapies would be appropriate.

METHODS

Response to GC, as defined by the reduction of the absolute eosinophil count to below 1000/mm3 and control of symptoms, was assessed by a retrospective chart review of subjects with PDGFRA-negative HES evaluated on an institutional review board-approved protocol. Demographic, clinical, and laboratory parameters obtained before institution of GC, as well as final diagnosis, were evaluated to determine predictors of GC response. Proportional odds models were used for univariate and multivariate assessment of predictors with permutation adjusted P values to correct for multiple comparisons.

RESULTS

A total of 164 subjects with PDGFRA-negative HES were categorized according to GC response. Of them, 39% of the subjects responded to low dose (≤10 mg) prednisone, 9% did not respond to GC, and the remainder (52%) had variable responses to GC. The HES subtype diagnosis was the best predictor of response to GC with myeloid forms and lymphocytic variants of HES being the least responsive to GC.

CONCLUSIONS

In a large cohort of well-characterized subjects with HES, the odds of response to GC was predicted by HES subtype. Using this model, clinicians may more readily proceed to second-line agents in subjects with confirmed lymphocytic or myeloid forms of HES.

Clinical and Biological Markers in Hypereosinophilic Syndromes

Hypereosinophilic syndromes (HES) are rare, heterogeneous syndromes characterized by markedly elevated eosinophil counts in the blood and/or tissue and evidence of eosinophil-associated pathology. Although parasitic infections, drug hypersensitivity, and other disorders of defined etiology can present as HES (associated HES), treatment is directed at the underlying cause rather than the eosinophilia itself. A number of additional subtypes of HES have been described, based on clinical and laboratory features. These include (1) myeloid HES—a primary disorder of the myeloid lineage, (2) lymphocytic variant HES—eosinophilia driven by aberrant or clonal lymphocytes secreting eosinophil-promoting cytokines, (3) overlap HES—eosinophilia restricted to a single organ or organ system, (4) familial eosinophilia—a rare inherited form of HES, and (5) idiopathic HES. Since clinical manifestations, response to therapy, and prognosis all differ between HES subtypes, this review will focus on clinical and biological markers that serve as markers of disease activity in HES (excluding associated HES), including those that are likely to be useful only in specific clinical subtypes.