A diagnostic approach that may help to discriminate inherited thrombocytopenia from chronic immune thrombocytopenia in adult patients

Macrothrombocytopenia: Role of Automated Platelet Data in Diagnosis

Purpose

Inherited macrothrombocytopenia is an underdiagnosed condition and may result in misdiagnosis and inappropriate management. This research was done to study this condition in a hospital setting.

Materials and Methods

This study was conducted over 6 months in a teaching hospital. Patients whose complete blood count (CBC) samples were sent to the hematology laboratory were included. Patients were suspected to have inherited macrothrombocytopenia according to pre-defined criteria. Demographic information, automated CBC and peripheral smear examination was carried out. Seventy five healthy individuals and 50 patients with secondary thrombocytopenia were also analyzed.

Results

Likely inherited macrothrombocytopenia was identified in 75 patients. Automated platelet count in these patients ranged from 26 × 10^9/L to 106 × 10^9/L while MPV ranged from 11.0 to 13.6 fL. There was significant difference (p < .001) in mean platelet volume (MPV) and platelet large cell ratio (P-LCR) amongst patients with likely inherited macrothrombocytopenia, those with secondary thrombocytopenia and the control group. Mean platelet diameter was significantly higher (3.5 ± 1.1μm) in patients with likely inherited macrothromboctopenia compared to those with secondary thrombocytopenia (2.4 ± 0.7μm) and control group (1.9 ± 0.7μm). All patients with suspected inherited macrothrombocytopenia showed abnormal platelet histograms with descending limb in the high volume and red cell zone. Four distinct histogram patterns were identified.

Conclusion

Inherited macrothrombocytopenia is an underdiagnosed condition. The patient's history, clinical examination, judicious use of automated CBC data including platelet histograms and careful review of the peripheral blood smear are useful tools to suspect this condition.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12288-022-01590-6.

The effects of mean platelet volume and red cell distribution width on prognosis in patients with myelodysplastic syndrome

Objective: In this study, the relationship between changes in mean platelet volume (MPV) and erythrocyte distribution width (RDW) with hematological response and survival in patients with myelodysplastic syndrome was investigated. Patients and Methods: Between 1 January 2011 and 31 December 2018, patient characteristics and hemogram results were evaluated during the treatment process among 158 patients diagnosed with myelodysplastic syndrome. Results: The mean age of the patients who were included in the study was 71.53±12.6 years. The MPV percentage change in the 2-year follow-up of the patients with and without hematological response was significant, at 0.022±0.11 (2.2%) in those who responded and at 0.069±0.15 (6.9%) in those who did not (p=0.049). Throughout the same period, the degree of RDW changes in the patients who died was 13.23±22.97, the degree in those who survived was 2.86±21.42, and the difference between the two groups was statistically significant (p=0.006). Conclusion: In patients diagnosed with myelodysplastic syndrome, MPV and RDW values can be considered inexpensive and simple laboratory markers that can be used in follow-ups and promising tests to predict both treatment response and survival in the early period and change treatment modalities.

Primary immune thrombocytopenia: a 'diagnosis of exclusion'?

Current diagnosis of primary immune thrombocytopenia (ITP) is presumptive, centered on excluding other causes of thrombocytopenia. The diagnosis of ITP is challenging because of the wide range of potential inherited and acquired causes of thrombocytopenia. The treatment of ITP is empiric with steroids, high-dose immunoglobulin, immunosuppressants and thrombopoietin agonists with potential side effects. We searched Medline and Cochrane databases, reviewed the study data and analyzed the individual diagnostic tests for their evidence-based role in the diagnosis of ITP. We then analyzed the strength of the scientific evidence for each diagnostic test in the diagnosis of ITP and identified gaps in the diagnostic accuracy. The diagnostic challenges in ITP include: insufficient evidence for the individual test for diagnosis of ITP, no standardized protocol/guideline for diagnosis, hurdles in accessing the available resources and failure to correlate the clinical data while reviewing the blood smear. We did not identify a diagnostic test that clinicians can use to confirm the diagnosis of ITP. In the absence of a diagnostic test of proven value in ITP, the clinician is best served by a comprehensive history and physical examination, complete blood count and review of the peripheral blood smear in evaluating thrombocytopenia.

An Update on Pediatric Immune Thrombocytopenia (ITP): Differentiating Primary ITP, IPD, and PID

Immune thrombocytopenia (ITP) is the most common acquired thrombocytopenia in children and is caused by both immune-mediated decreased platelet production and increased platelet destruction. In the absence of a diagnostic test, ITP must be differentiated from other thrombocytopenic disorders, including inherited platelet disorders (IPD). In addition, a diagnosis of secondary ITP due to a primary immune deficiency (PID) with immune dysregulation may not be apparent at diagnosis but can alter management and should be considered in an expanding number of clinical scenarios. The diagnostic evaluation of children with thrombocytopenia will vary based on the clinical history and laboratory features. Access to genotyping has broadened the ability to specify the etiology of thrombocytopenia, while increasing access to immunophenotyping, functional immunologic and platelet assays, and biochemical markers has allowed for more in-depth evaluation of patients. With this greater availability of testing, diagnostic algorithms in patients with thrombocytopenia have become complex. In this article, we highlight the diagnostic evaluation of thrombocytopenia in children with a focus on ITP, including consideration of underlying genetic and immune disorders, and utilize hypothetical patient cases to describe disease manifestations and strategies for treatment of pediatric ITP.

Platelet function and bleeding at different phases of childhood immune thrombocytopenia

Immune thrombocytopenia (ITP) is believed to be associated with platelet function defects. However, their mechanisms are poorly understood, in particular with regard to differences between ITP phases, patient age, and therapy. We investigated platelet function and bleeding in children with either persistent or chronic ITP, with or without romiplostim therapy. The study included 151 children with ITP, of whom 56 had disease duration less than 12 months (grouped together as acute/persistent) and 95 were chronic. Samples of 57 healthy children were used as controls, while 5 patients with leukemia, 5 with aplastic anemia, 4 with MYH9-associated thrombocytopenia, and 7 with Wiskott-Aldrich syndrome were used as non-ITP thrombocytopenia controls. Whole blood flow cytometry revealed that platelets in both acute/persistent and chronic ITP were increased in size compared with healthy donors. They were also pre-activated as assessed by PAC1, CD62p, cytosolic calcium, and procoagulant platelet levels. This pattern was not observed in other childhood thrombocytopenias. Pre-activation by CD62p was higher in the bleeding group in the chronic ITP cohort only. Romiplostim treatment decreased size and pre-activation of the patient platelets, but not calcium. Our data suggest that increased size, pre-activation, and cytosolic calcium are common for all ITP platelets, but their association with bleeding could depend on the disease phase.

Misdiagnosed thrombocytopenia in children and adolescents: analysis of the Pediatric and Adult Registry on Chronic ITP

Primary immune thrombocytopenia (ITP) in children is a diagnosis of exclusion, but cases of secondary ITP and nonimmune thrombocytopenia (non-IT) are generally difficult to recognize in a timely fashion. We describe a pediatric population with a revised diagnosis of secondary ITP or non-IT within 24 months of follow-up. Data were extracted from the Pediatric and Adult Registry on Chronic ITP, an international multicenter registry collecting data prospectively in patients with newly diagnosed primary ITP. Between 2004 and 2019, a total of 3974 children aged 3 months to 16 years were included. Secondary ITP and non-IT were reported in 113 patients (63 female subjects). Infectious (n = 53) and autoimmune (n = 42) diseases were identified as the main causes, with median ages at diagnosis of 3.2 years (interquartile range: 1.2; 6.7 years) and 12.4 years (interquartile range: 7.6; 13.7 years), respectively. Other causes included malignancies, aplastic anemia, immunodeficiency, and drug use. Patients with malignancy and aplastic anemia had significantly higher initial platelet counts (37 and 52 × 109/L) than did those with infection or autoimmune diseases (12 and 13 × 109/L). Characteristics of patients with secondary ITP due to infection were similar to those of children with primary ITP at first presentation, indicating similar mechanisms. Significant differences were found for age, sex, comorbidities, initial bleeding, sustained need for treatment, and disease persistence for the remaining noninfectious group compared with primary ITP. Based on our findings, we propose a diagnostic algorithm that may serve as a basis for further discussion and prospective trials.

Second-line treatment trends and long-term outcomes of 392 children with chronic immune thrombocytopenic purpura: the French experience over the past 25 years

Childhood chronic immune thrombocytopenic purpura (cITP) is a rare disease. In severe cases, there is no evidence for the optimal therapeutic strategy. Our aim was to describe the real-life management of non-selected children with cITP at diagnosis. Since 2004, patients less than 18 years old with cITP have been enrolled in the national prospective cohort, OBS'CEREVANCE. From 1990 to 2014, in 29 centres, 392 children were diagnosed with cITP. With a median follow-up of six years (2·0-25), 45% did not need second-line therapy, and 55% (n = 217) received one or more second lines, mainly splenectomy (n = 108), hydroxychloroquine (n = 61), rituximab (n = 61) or azathioprine (n = 40). The overall five-year further second-line treatment-free survival was 56% [95% CI 49·5-64.1]. The use of splenectomy significantly decreased over time. Hydroxychloroquine was administered to children with positive antinuclear antibodies, more frequently older and girls, and reached 55% efficacy. None of the patients died. Ten years after the initial diagnosis, 55% of the 56 followed children had achieved complete remission. Children with cITP do not need second-line treatments in 45% of cases. Basing the treatment decision on the pathophysiological pathways is challenging, as illustrated by ITP patients with positive antinuclear antibodies treated with hydroxychloroquine.

A new NOTCH3 damaging variant in a thrombocytopenia family of Miao ethnic group

BACKGROUND

Pediatric inherited thrombocytopenia, also known as a deficiency of platelets in children, is caused by genetic factors and it is hard to obtain an effective treatment. Thus, it is necessary to identify the possible genetic variants that are responsible for thrombocytopenia.

METHODS

Whole exome sequencing was used to detect genetic variants in two members of a thrombocytopenia family of Miao ethnic group. Multiple in silico analyses were performed to evaluate the effects of the novel missense variants.

RESULTS

Finally, a novel variant (chr19: g.15170364G>A) in the NOTCH3 gene was found, as confirmed with Sanger sequencing, which could result in a R1694Q substitution in the protein. This variant was consistently suggested to be damaging by sift (Sorting Tolerant From Intolerant; http://sift.jcvi.org), polyphen (Polymorphism Phenotyping, version 2.0; http://genetics.bwh.harvard.edu/pph2) and mutationtaster (http://www.mutationtaster.org) software. By building the 3D model of the key region of NOTCH3 protein and performing the structure simulation, we found that (i) this variant affected the 3D structure model with a root-mean-square deviation = 0.46 between wild-type and mutant type; (ii) this variant caused the protein to reduce the solvent accessible surface area by 421 Å² ; and (iii) compared to the wild-type protein, the mutant protein had two less amino acids to maintain protein stability.

CONCLUSIONS

A novel damaging variant in the NOTCH3 gene was identified in a thrombocytopenia family with respect to decreasing the stability of NOTCH3, which may help with the prognosis and therapy of inherited thrombocytopenia.

Inherited Platelet Disorders: A Modern Approach to Evaluation and Treatment

The inherited platelet disorders are a heterogeneous group of disorders that can be pleotropic in their clinical presentations. They may present with variable platelet counts and bleeding, making their diagnosis difficult. New diagnostic tools range from flow cytometric platelet function assessments to next-generation sequencing. Several platelet disorders may now be treated with gene therapy or bone marrow transplant. Improved understanding of the molecular and biologic mechanisms of the inherited platelet disorders may lead to novel targeted therapies.

Prevalence of Macrothrombocytopenia in Healthy College Students in Western India

Macrothrombocytopenia is being increasingly described across the globe. There is paucity of data on the prevalence of this condition from different parts of India. 10,047 healthy college students from the city of Surat in western India were investigated for macrothrombocytopenia i.e. those with Mean platelet Volume of > 11 fL and platelet count of less than 150 × 10⁹/L. ABO blood groups, complete blood counts, peripheral smear examination and haemoglobinopathy work up was also done. Siblings and parents of the macrothrombocytopenic individuals were also studied when available. Bleeding assessment tool of International society of thrombosis and haemostasis were applied to see if there were excessive bleeding in macrothrombocytropenia patients. One hundred and ninety-six students (1.95%) had asymptomatic macrothrombocytopenia. More female students (P < 0.0001) had this condition and blood group A was under represented (P = 0.019) with this condition. Prevalence of macrothrombocytopenia was not related to ethnic subgroups to which the students belonged to, nor was it linked to presence of any haemoglobinopathy gene. In 38 of the 52, 1st degree relatives studied macrothrombocytopenia was confirmed at least in one of them. Excessive bleeding in none of the individuals with macrothrombocytopenia was noted. Asymptomatic macrothrombocytopenia is rare in western parts of India and affects 1.95% of the healthy population. Females were over represented with this condition raising a suspicion of X linked dominant inheritance. Underrepresentation of blood group A in this condition requires further study.

Inherited Macrothrombocytopenia: Correlating Morphology, Epidemiology, Molecular Pathology and Clinical Features

Inherited macrothrombocytopenia is increasingly being recognized as a relatively common condition. This descriptive review aims at focusing on the different areas of advancement that have taken place with this condition with particular reference to India. A pubmed search of articles between January 1990 and October 2017 with the key words-macrothrombocytopenia, asymptomatic macrothrombocytopenia, macrothrombocytopenia India, syndromic macrothrombocytopenia, molecular pathology, megakaryopoiesis and platelet formation were searched. The shortlisted articles were then read. Review articles provided additional references and the articles thus obtained were also read. Special interest and research conducted by the authors provided further sources of information. A total of 487 articles were found of which 68 articles were related to our subject of review. Review articles were read and additional articles from the reference quoted. Forty-four percent of nonsyndromic Inherited macrothrombocytopenia showed mutations of MYH9, GP1BB, GP1Ba, GPIX, ABCG5 and 8, ACTN, FLI, TUBB and RUNX1 frequently in heterozygous state. All types of inheritance pattern namely autosomal dominant, recessive and sex linked patterns have been described. Syndromic causes of this phenomenon are well known and have been described. Many asymptomatic patients do have mild or moderate bleeding history. Clinical algorithms to differentiate chronic ITP associated macrothrombocytopenia from inherited variety have been explored. Inherited macrothrombocytopenia is an emerging area of interest in platelet biology with its implication in diagnosis, prognosis, genetic counseling, management and in transfusion medicine.

Mean platelet component and mean platelet volume as useful screening markers for myelodysplastic syndrome

BACKGROUND

Hematologic disorders, including myelodysplastic syndrome (MDS), are difficult to identify in routine hematologic examinations using automated hematology analyzers. However, the practical uses of mean platelet component and mean platelet volume (MPV) measured by these analyzers as screening markers for MDS, remain unclear.

METHODS

Mean platelet component and MPV values were measured in the peripheral blood of patients with MDS, aplastic anemia, idiopathic thrombocytopenic purpura, myeloproliferative neoplasms, and in healthy controls using an automated hematologic analyzer. Cutoff values for discriminating between the MDS group and healthy controls were determined by recursive partitioning analysis.

RESULTS

Mean platelet component was significantly lower in MDS patients compared with controls, while MPV was significantly higher. Combined cutoff values for MDS diagnosis of <25.3 g/dL for mean platelet component and >10.0 fL for MPV showed a specificity and positive predictive value of 99.9% and 99.1%, respectively. These cutoff values also differentiated between MDS and diagnoses of aplastic anemia, idiopathic thrombocytopenic purpura, and myeloproliferative neoplasms.

CONCLUSION

Mean platelet component and MPV may, thus, be useful and convenient screening markers for MDS.

Mean platelet diameter measurements to classify inherited thrombocytopenias

INTRODUCTION

Mean platelet volume (MPV) assists the differential diagnosis of inherited thrombocytopenia (IT) but lacks standardisation and varies between automated analysers. Classification of IT based on mean platelet diameter (MPD) has been proposed by an international collaborative study but has not been validated.

METHODS

To assess the applicability of MPD to classify forms of IT, digital images of blood films from patients with established genetic causes for IT were generated, and the MPD measured (ZEISS Axio-scanner and Image J software) by a blinded reviewer. Comparison was made to the proposed classification system.

RESULTS

Mean platelet volume was measured in thrombocytopenia with different genetic aetiologies, bilallelic BSS (bBSS) (n = 1), monoallelic BSS (mBSS) (n = 2), MYH9-related disorders (MYH9-RD) (n = 11), GFI1B-related thrombocytopenia (RT) (n = 15), FLI1-RT (n = 2), TUBB1-RT (n = 3), ITGA2B/ITGB3-RT (n = 1), RUNX1-RT (n = 2) and controls (n = 54). bBSS and 82% of MYH9-RD samples had MPD >4 μm which correlated with "IT with giant platelets." Only 55% of samples expected in the "large platelet group" had MPD meeting the classification cut-off (MPD >3.2 μm). FLI1-RT MPD were significantly larger than expected whilst ITGA2B/ITGB3-RT MPD were smaller than proposed. MPD in FPD/AML were "normal."

CONCLUSION

Platelet MPD measurements are a useful guide to classify IT, but the time taken to record measurements may limit clinical applicability.

Wiskott-Aldrich syndrome in a child presenting with macrothrombocytopenia

Wiskott-Aldrich syndrome (WAS) is a rare X-linked recessive disease resulting from variants in the WAS gene, characterized by a triad of immunodeficiency, eczema, and thrombocytopenia. Despite the fact that WAS is traditionally differentiated from immune thrombocytopenia (ITP) by small size of WAS platelets, in practice, microthrombocytopenia may occasionally not be present, and in certain cases, WAS patients exhibit some parallelism to ITP patients. We characterized one patient presenting with the classic form of the disease but increased mean platelet volume. Molecular studies revealed a novel hemizygous 1-bp deletion in WAS gene, c.802delC, leading to a frameshift and stop codon at amino acid 308 (p.Arg268Glyfs*40). Next-generation sequencing of a total of 70 additional genes known to harbor variants implicated in inherited platelet disorders did not identify additional defects. The pathogenesis of macrothrombocytopenia in this case is not known, but probably the coexistence of a still unidentified additional genetic variant might be involved.

Diagnosis and management of immune thrombocytopenia in childhood

Evidence-based medicine is growing in immune thrombocytopenia (ITP), but solid clinical data are still lacking in many areas. A majority of children has self-limited ITP, but chronic symptomatic ITP exists also in pediatrics. Management includes a watch-and-wait strategy for children with newly diagnosed ITP and no or mild bleeding, and immunoglobulins and corticosteroids, if more bleeding and mucous membrane involvement is present. Treatment endpoints differ in clinical research and in clinical practice. The requirement of platelet enhancing drugs needs to be better defined in guidelines. Second-line therapies for children are rarely required and include thrombopoietin-receptor agonists, rituximab, dexamethasone and immunosuppressants. Thrombopoietin-receptor agonists are successful in adult but also in pediatric ITP. The strategical position of splenectomy differs from that in adults. Although effective in children it is less frequently used because of its life-long cumulative risk of infectious diseases and a higher potential of spontaneous remission in ITP, providing a strong argument to defer splenectomy. The rarity of ITP makes clinical research expensive.