Bone marrow histology for the diagnosis of essential thrombocythemia in children: a multicenter Italian study

Clinical and molecular characteristics of forty Chinese children with essential thrombocythemia: A single-center, retrospective analysis

Due to the infrequency of essential thrombocythemia (ET) in children, little is known about its pathophysiological mechanism. To learn about the clinical and molecular features of Chinese children with ET, we retrospectively analysed 40 children with ET in a single center from 2015-2021. More than half of the children (51.3%, 20/39) were asymptomatic at diagnosis. Nearly half of the children (48.7%, 19/39) had microvascular symptoms, including headache, dizziness, stomachache, and paresthesia. Only two cases experienced vascular events. The proportion of children with typical "driver gene mutations" (i.e., JAK2 p.V617F, CALR exon 9, or MPL exon 10 mutation) was low (12.5%, 5/40). The equivalent ratio of children carried atypical driver gene mutations; however, 30 (75%) patients did not harbour driver gene mutations. Children carrying JAK2 p.V617F had lower platelet count (938 × 10⁹ /L vs. 1654 × 10⁹ /L, p = 0.031) compared to those without driver gene mutations. Cases harbouring typical driver mutations had higher median WBC counts than those without driver gene mutations (15.14 × 10⁹ /L vs. 8.01 × 10⁹ /L, p = 0.015). Compared to those without driver gene mutations, cases carrying typical and atypical driver gene mutations were both younger (median ages were 12, 6, and 7 years old, respectively; p = 0.023). The most prevalent non-driver gene mutations and those mutations with prognostic significance in adult counterparts were less common in children with ET compared to adults with ET.

Real world study of children and young adults with myeloproliferative neoplasms identifying risks and unmet needs

In a contemporary cohort of 444 young MPN patients, risks of thrombosis, hemorrhage, and transformation were 1% pt/y.

Current risk scores had no utility. Uniquely, we identify that splenomegaly and hyperviscosity symptoms predict thrombosis and transformation.

Myeloproliferative neoplasms (MPNs) are uncommon in children/young adults. Here, we present data on unselected patients diagnosed before 25 years of age included from 38 centers in 15 countries. Sequential patients were included. We identified 444 patients, with median follow-up 9.7 years (0-47.8). Forty-nine (11.1%) had a history of thrombosis at diagnosis, 49 new thrombotic events were recorded (1.16% patient per year [pt/y]), perihepatic vein thromboses were most frequent (47.6% venous events), and logistic regression identified JAK2V617F mutation (P = .016) and hyperviscosity symptoms (visual disturbances, dizziness, vertigo, headache) as risk factors (P = .040). New hemorrhagic events occurred in 44 patients (9.9%, 1.04% pt/y). Disease transformation occurred in 48 patients (10.9%, 1.13% pt/y), usually to myelofibrosis (7.5%) with splenomegaly as a novel risk factor for transformation in essential thrombocythemia (ET) (P= .000) in logistical regression. Eight deaths (1.8%) were recorded, 3 after allogeneic stem cell transplantation. Concerning conventional risk scores: International Prognostic Score for Essential Thrombocythemia-Thrombosis and new International Prognostic Score for Essential Thrombocythemia-Thrombosis differentiated ET patients in terms of thrombotic risk. Both scores identified high-risk patients with the same median thrombosis-free survival of 28.5 years. No contemporary scores were able to predict survival for young ET or polycythemia vera patients. Our data represents the largest real-world study of MPN patients age < 25 years at diagnosis. Rates of thrombotic events and transformation were higher than expected compared with the previous literature. Our study provides new and reliable information as a basis for prospective studies, trials, and development of harmonized international guidelines for the specific management of young patients with MPN.

Essential Thrombocythemia in Children and Adolescents

Simple Summary

Among chronic Ph-negative myeloproliferative neoplasms, essential thrombocythemia is found in children with low but increasing incidence. The diagnostic and clinical features do not completely overlap with ET of adult age. A significant number of cases, in fact, do not meet the criteria of clonality, and many cases require extensive clinical evaluation to exclude secondary, reactive forms. Therefore, histological analysis of bone marrow biopsy is necessary, and its use should be enforced. The clinical course appears to be more benign, at least within the first decades of observation, with the incidence of thrombotic events being much lower than in adults (4 % vs. 30%). Hemorrhages are mostly irrelevant. Therefore, the management should be carefully adapted to the individual patient, balancing the risk of future complications with long-term collateral effects of any drug. This review analyzes the peculiarities of the disease facing similarities and differences with adult scenarios.

Abstract

This paper reviews the features of pediatric essential thrombocythemia (ET). ET is a rare disease in children, challenging pediatric and adult hematologists alike. The current WHO classification acknowledges classical Philadelphia-negative MPNs and defines diagnostic criteria, mainly encompassing adult cases. The presence of one of three driver mutations (JAK2V617F, CALR, and MPL mutations) represent the proof of clonality typical of ET. Pediatric ET cases are thus usually confronted by adult approaches. These can fit only some patients, because only 25–40% of cases present one of the driver mutations. The diagnosis of hereditary, familial thrombocytosis and the exclusion of reactive/secondary thrombocytosis must be part of the diagnostic process in children and can clarify most of the negative cases. Still, many children present a clinical, histological picture of ET, with a molecular triple wild-type status. Moreover, prognosis seems more benign, at least within the first few decades of follow-up. Thrombotic events are rare, and only minor hemorrhages are ordinarily observed. As per the management, the need to control symptoms must be balanced with the collateral effects of lifelong drug therapy. We conclude that these differences concert a compelling case for a very careful therapeutic approach and advocate for the importance of further cooperative studies.

Pediatric Myeloproliferative Neoplasms

Myeloproliferative neoplasms can present early in life and may present a diagnostic challenge. Very few studies have focused on the diagnosis, prognosis, and therapy for pediatric myeloproliferative neoplasms. This article focuses on chronic myeloid leukemia, essential thrombocythemia, polycythemia vera, and primary myelofibrosis in children.

Low-Risk Essential Thrombocythemia: A Comprehensive Review

Essential thrombocythemia (ET) is a chronic myeloproliferative neoplasm characterized by a persistently elevated platelet count in the absence of a secondary cause. The clinical consequences of uncontrolled thrombocytosis can include both thrombosis and hemorrhage. Patients with features conferring a “high risk” of vascular events benefit from reduction of the platelet count through cytoreductive therapy. The management of patients who lack such high-risk features has until recently been less well defined, but it is now apparent that many require minimal or even no intervention. In this review, we discuss the diagnostic pathway for younger patients with unexplained thrombocytosis, including screening molecular investigations, the role of bone marrow biopsy, and investigations in those patients negative for the classic myeloproliferative neoplasm driver mutations (JAK2, CALR, MPL). We discuss conventional and novel risk stratification methods in essential thrombocythemia and how these can be best applied in clinical practice, particularly in the era of more comprehensive genomic testing. The treatment approach for “low risk” patients is discussed including antiplatelets and the options for cytoreductive therapy, if indicated, together with areas of clinical need for future study.

Essential thrombocythemia A retrospective case series

BACKGROUND

Essential thrombocythemia (ET) is rare in children, and pediatric guidelines are lacking. Therefore, we aimed to evaluate ET diagnosis and treatment in a pediatric cohort.

PROCEDURE

Data of patients with ET from three hospitals were reviewed. Molecular diagnosis included JAK2V617F, CALR, and MPL mutations. Patients were evaluated for acquired von Willebrand syndrome (AVWS). Follow-up included clinical symptoms, adverse events, and treatment.

RESULTS

Twelve children (median age: 8 years, range 1-14.5) were included. Mean lag period between the first documentation of thrombocytosis until ET diagnosis was 36 months. Six patients were positive for JAK2V617F and two for CALR mutations. In six of nine patients, AVWS was diagnosed. At diagnosis, only 33% of patients started therapy with aspirin (n = 4) and hydroxyurea (n = 2). In three of eight untreated patients, therapy was added during follow-up. The cohort was followed for a median of 32.5 months (range: 4-108 months). Clinical follow-up disclosed vascular complications in 4 of 12 patients (deep vein thrombosis, n = 1; transient ischemic attack, n = 3). Two females experienced excessive bleeding; both were diagnosed with AVWS. Neither leukemia nor myelofibrosis evolved in our cohort.

CONCLUSION

Increased awareness to pediatric ET is warranted, as delayed diagnosis is common. Compared to adults, AVWS may be more prevalent among children with ET.

Myeloproliferative Neoplasms in Children, Adolescents, and Young Adults

PURPOSE OF REVIEW

Myeloproliferative neoplasms are traditionally seen in older adults, making them poorly understood in younger patients. Clinical presentation, genetic landscape, outcomes, and best management practices are inadequately described in this group. Over the past decade, more research has focused on younger patients, and this paper seeks to review and describe the current status of the field.

RECENT FINDINGS

A recent review analyzed the available pediatric MPN literature and highlighted the paucity of published data. Pediatric patients showed lower rates of the common mutations found in adults, thrombotic events, and disease transformation to myelofibrosis and acute leukemia. A number of centers have recently shared their experience with young adult patients. Better survival outcomes were confirmed for young adult patients compared to older patients. There is still much to learn about myeloproliferative neoplasms in pediatric and young adult patients, but currently available data showing better outcomes is reassuring.

Quantification of IGF-1 receptor is useful in the differential diagnosis of essential thrombocytosis from reactive thrombocytosis

BACKGROUND

To make a definite diagnosis of essential thrombocytosis (ET) from reactive thrombocytosis (RT), the most reliable criteria are the presence of driver mutations, namely JAK2, CALR, or MPL gene mutations. In the absence of these driver mutations, so-called triple-negative ET, the differential diagnosis could be difficult. Although bone marrow biopsy could be helpful, it may be difficult in some cases, to do gene sequence analysis to identify other clonal marker gene mutations than the driver mutations, as only very few were found.

METHODS

IGF-1R quantification by flow cytometry in mononuclear cells (MNC) from peripheral blood was performed in 33 patients with ET (untreated or off treatment with hydroxyurea), 28 patients with RT, and 16 normal volunteer controls.

RESULTS

We found IGF-1R levels were significantly elevated in ET patients compared to RT patients or controls. A cutoff value of 253 was chosen from the logistic regression to predict each patient's group, a value ≥253 meant that a patient belonged to the ET group (sensitivity 96.4% and specificity 68.6%).

CONCLUSION

We suggest that adding quantification of IGF-1R in blood MNC by flow cytometry is useful in differentiating ET from RT.

Contemporary management of essential thrombocythemia in children

INTRODUCTION

Essential thrombocythemia (ET) is a disease which is extremely rare in children. Only recently, data on pediatric ET have become available. Areas covered: In children with sustained platelet count over 450 x 10⁹/L, secondary thrombocytosis must be ruled out. ET workup comprehends research of JAK2V617F, CALR and MPL mutations and bone marrow biopsy (BM). In asymptomatic children wait and watch is the best option. Aspirin controls headache and other microvascular disturbances. Patients with venous thrombosis need anticoagulation. Cytoreductive drugs in children with ET should be prescribed as a last choice. Hydroxyurea and IFN-a are first-line therapy at any age including children; Anagrelide is not licensed as first-line therapy for ET in Europe. New JAK2-inhibitors are not clearly useful in ET and hence not approved for ET. Expert opinion: The most challenging problem is to understand if a child with prolonged not secondary thrombocytosis really has ET. Diagnostic workup requires molecular and histological studies. The rare children with clonal ET have features like those of adults. Patients with ET have long expected survival and the treatment in children must be long-term efficacious and well tolerated.

Characteristics and outcomes of patients with essential thrombocythemia or polycythemia vera diagnosed before 20 years of age: a systematic review

Although it is well known that myeloproliferative neoplasms occur in younger patients, few large cohorts of such patients have been reported. Thus, our knowledge about circumstances of diagnosis, outcome and treatment is limited, especially for children and young adults. We therefore performed a systematic review of cases, published since 2005, concerning patients aged below 20 years at the time of diagnosis of essential thrombocythemia or polycythemia vera. We identified 396 cases of essential thrombocythemia and 75 of polycythemia vera. The median age at diagnosis was 9.3 and 12 years, respectively, and females constituted 57.6% and 45% of the groups, respectively. Half of the patients were asymptomatic at diagnosis. The proportion of so-called triple negativity was high: 57% in essential thrombocythemia and 73% in polycythemia vera. The incidence of thrombosis during the follow-up was 9.3% in patients with polycythemia vera and less, 3.8%, in those with essential thrombocythemia. Venous events were predominant (84.2%), with hemorrhagic episodes being rarer (<5%). The risk of evolution also seemed low (2% to myelofibrosis and no reports of acute leukemia), but the median follow-up was only 50 months. Survival curves were not available. Half of the patients received an antithrombotic drug and 40.5% received a cytoreductive drug. All data should be analyzed with care because of the proportion of missing data (10.7% to 74.7%). This review highlights interesting points concerning this population of young patients with myeloproliferative neoplasms, including that such patients were identified as negative for all common driver mutations, but also shows the need for larger contemporary cohorts with longer follow-up to assess the true prognosis of these patients.