Identification of inherited macrothrombocytopenias based on mean platelet volume among patients diagnosed with idiopathic thrombocytopenia

Prevalence of constitutional macrothrombocytopenia in the immigrants of Northern and Eastern states of India

Background

Thrombocytopenia is generally alarming to both clinicians and patients as the consequence can be disastrous. However, some of the conditions associated with thrombocytopenia can be innocuous. Unless this is recognized, detection of thrombocytopenia results in series of further investigations and management plan by clinicians. Hematological investigation in an apparently healthy/asymptomatic individual can throw up many surprises. One of them is thrombocytopenia and giant platelets on peripheral smear examination. Asymptomatic constitutional macrothrombocytopenia (also called as Harris platelet syndrome) is increasingly recognized in north and eastern parts of India. However, this condition is nearly unknown in southern part of our country. With Increased immigrants to south India from northern and eastern states, it becomes imperative for both clinicians and lab physicians to be aware of the magnitude of the condition and interpret appropriately. This can avoid unnecessary anxiety and investigations.

Materials and Methods

Blood samples from 300 north and northeastern immigrants (Cases) and equal number of healthy subjects from south India (Controls) were examined for hematological parameters. Peripheral smears were examined for the presence of giant platelets. Results: Constitutional macrothrombocytopenia was seen in 4.3% of the cases and in 0.66% of the controls. The difference was statistically significant with a Fischer exact P value of 0.0067. The prevalence of macrothrombocytopenia on subjective assessment of peripheral smear was 6.7% in the cases and 1% in the control group.

Conclusions

The prevalence of Harris platelet syndrome was found to be 4.3% in the immigrants from north and northeastern states.

Application of high-throughput sequencing for hereditary thrombocytopenia in southwestern China

Background

The aim of this study was to design and analyze the applicability of a 21‐gene high‐throughput sequencing (HTS) panel in the molecular diagnosis of patients with hereditary thrombocytopenia (HT).

Methods

A custom target enrichment library was designed to capture 21 genes known to be associated with HTs. Twenty‐four patients with an HT phenotype were studied using this technology.

Results

One pathogenic variant on the MYH9 gene and one likely pathogenic variant on the ABCG8 gene previously known to cause HTs were identified. Additionally, 3 previously reported variants affecting WAS, ADAMTS13, and GP1BA were detected, and 9 novel variants affecting FLNA, ITGB3, NBEAL2, MYH9, VWF, and ANKRD26 genes were identified. The 12 variants were classified to be of uncertain significance.

Conclusion

Our results demonstrate that HTS is an accurate and reliable method of pre‐screening patients for variants in known HT‐causing genes. With the advantage of distinguishing HT from immune thrombocytopenia, HTS could play a key role in improving the clinical management of patients.

Regional Anaesthesia in Harris Platelet Syndrome for Transurethral Resection of Prostate-A Clinical Conundrum or Certitude?

Routine use of the autoanalyzer has helped uncover the increasing incidence of thrombocytopenia. Disorders associated with macrothrombocytes with thrombocytopenia necessitate a preoperative evaluation to assess the bleeding tendencies and the need for transfusion of blood products. Harris platelet syndrome is one such disorder where macrothrombocytes with thrombocytopenia are associated with no congenital abnormalities and low risk of bleeding intraoperatively. There are cases where Harris platelet syndrome has been treated with steroids or splenectomy, which is unwarranted. We report successful management of a patient with Harris platelet syndrome who underwent transurethral resection of the prostate under spinal anaesthesia with no complications.

Application of High-Throughput Sequencing in the Diagnosis of Inherited Thrombocytopenia

Inherited thrombocytopenia is a group of hereditary diseases with a reduction in platelet count as the main clinical manifestation. Clinically, there is an urgent need for a convenient and rapid diagnosis method. We introduced a high-throughput, next-generation sequencing (NGS) platform into the routine diagnosis of patients with unexplained thrombocytopenia and analyzed the gene sequencing results to evaluate the value of NGS technology in the screening and diagnosis of inherited thrombocytopenia. From a cohort of 112 patients with thrombocytopenia, we screened 43 patients with hereditary features. For the blood samples of these 43 patients, a gene sequencing platform for hemorrhagic and thrombotic diseases comprising 89 genes was used to perform gene detection using NGS technology. When we combined the screening results with clinical features and other findings, 15 (34.9%) of 43patients were diagnosed with inherited thrombocytopenia. In addition, 19 pathogenic variants, including 8 previously unreported variants, were identified in these patients. Through the use of this detection platform, we expect to establish a more effective diagnostic approach to such disorders.

My patient is thrombocytopenic! Is (s)he? Why? And what shall I do?

Solving the riddle of a thrombocytopenic patient is a difficult and fascinating task. The spectrum of possible aetiologies is wide, ranging from an in vitro artefact to severe treatment-resistant thrombocytopenic bleeding conditions, or even life-threatening prothrombotic states. Moreover, thrombocytopenia by itself does not protect from thrombosis and sometimes a patient with a low platelet count requires concomitant antithrombotic treatment as well. In order to identify and treat the cause and the effects of the thrombocytopenia, you have to put together several pieces of information, solving a unique jig-jaw puzzle.

The present work is not a textbook article about thrombocytopenia, rather a collection of differential diagnostic thoughts, treatment concepts, and some basic knowledge, that you can retrieve when facing your next thrombocytopenic patient. Enjoy reading it, but most importantly enjoy taking care of patients with a low platelet count. I bet the present work will assist you in this challenging and rewarding clinical task.

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.

Giant Platelets in Platelet Donors - A Blessing in Disguise?

INTRODUCTION

Inherited thrombocytopenias, including inherited giant platelet disorders (IGPD) are relatively rare, but their prevalence is probably underestimated. Harris platelet syndrome, the most common IGPD reported from Indian subcontinent, mostly from eastern part, is characterised by a low platelet count, high mean platelet volume (MPV) and absence of bleeding.

AIM

A short study was conducted to assess the prevalence of giant platelets in voluntary donors of single donor platelets (SDP) and analyse the effect of transfusion of such SDPs in patients.

MATERIALS AND METHODS

Voluntary donors of SDPs were screened as per standard guidelines prior to the procedure. A complete blood count (including MPV) along with a peripheral smear was done. A total of 45 donors were screened for plateletpheresis. Following plateletpheresis from these donors, a platelet count from the collection bag was done after one hour. The SDP was transfused as a single unit or divided into two and transfused to the same patient at two different occasions, as per clinical need. Platelet counts on pateints were done after one hour and the platelet recovery was noted.

RESULTS

Out of the 45 donors who were screened, 30 (66.67%) were found to have giant platelets. It was observed that the pre procedure platelet counts in donors having giant platelets were relatively low (1.5 -1.7 lacs) and so also the platelet yield (2.7-3x10(11)) compared to donors who did not, but the post transfusion platelet recovery was greater.

CONCLUSION

Since presence of giant platelets has been seen to be common in the Eastern part of India, a peripheral smear examination should always be considered during screening of plateletpheresis donors to avoid rejecting donors with giant platelets whose platelet counts are given falsely low by autoanalysers.

Platelet indices in Philadelphia-negative chronic myeloproliferative neoplasms / Indicii plachetari de volum în neoplasmele mieloproliferative cronice Philadelphia-negative

Introduction: Philadelphia-negative chronic myeloproliferative neoplasms (Ph-MPN): polycythemia vera (PV), essential thrombocythaemia (ET), and primary myelofibrosis (PMF) are characterized by an increased rate of thrombosis complications partly due to platelets activation. Large platelets are more active, have an enhanced procoagulant function and have a pathogenic role in arterial and venous thrombosis. In our study we tried to establish if platelet volume indices (MPV, PDW, P-LCR) issued from automated complete blood count determination are significantly different in Ph-MPN patients in comparison to healthy subjects. Materials and methods: Blood cell counts including platelet volume indices were assessed for 102 Ph-MPN and 102 healthy subjects using the impedance method on Sysmex XS 1000i and glucose and lipid profile, were assessed on Architect c 8000. Assessement of JAK2V617 positivity was conducted with amplification refractory mutation system polymerase chain reaction (ARMS-PCR), in whole peripheral blood. Results: Platelet volume indices (PVI) measured with the impedance based method, did not show significant differences in Ph-MPN patients in comparison to healthy controls. We noticed a moderate correlation between these indices and the presence of JAK2V617F mutation. PVI were increased in the small subgroup of patients treated with anagrelide and decreased in patients treated with simvastatin, comparatively with untreated patients. Conclusion: In our study we did not find a significant difference between platelet volume indices from Ph-MPN patients and healthy subjects. Further studies are required to demonstrate correlations between platelet volume indices and JAK2 V617F mutation, treatment with anagrelide and statins, respectively

Macrothrombocytopenia in north India: role of automated platelet data in the detection of an under diagnosed entity

Congenital macrothrombocytopenia is being increasingly recognised because of the increasing availability of automated platelet counts during routine complete blood count. If not recognised, these patients may be unnecessarily investigated or treated. The study was done to assess the occurrence of macrothrombocytopenia in the North Indian population and the role of automated platelet parameters in its detection. This prospective study was done on patients whose blood samples were sent for CBC to the hematology laboratory of a tertiary care hospital. Samples were run on Advia-120, a 5-part differential automated analyzer. Routine blood parameters including platelet count, mean platelet volume (MPV), platelet cytogram pattern and platelet flagging was studied along with peripheral blood smear examination. ANOVA was used to compare difference in mean MPV in patients with macrothrombocytopenia, and those with secondary thrombocytopenia and ITP. Seventy five (0.6 %) patients with CBC evaluation were detected to have macrothrombocytopenia, majority (96 %) of North Indian origin. The MPV (fl) in the 75 patients ranged from 10.9 to 23.3 (mean 15.1 ± 3.1 fl) with a dispersed cytogram pattern distinct from that seen in patients with normal platelet count, raised platelet count or low platelets due to secondary thrombocytopenia (MPV-10.9 ± 2.6) or ITP (10.8 ± 3.5). The difference in mean MPV in these patients was statistically significant (p < 0.00001). Macrothrombocytopenia is an under diagnosed condition and may be initially suspected on automated blood counts. Along with a blood smear examination, automated data (MPV and platelet cytogram pattern) aids the diagnosis and can avoid unnecessary investigations and interventions for these patients.

Spectrum of the mutations in Bernard-Soulier syndrome

Bernard-Soulier syndrome (BSS) is a rare autosomal recessive bleeding disorder characterized by defects of the GPIb-IX-V complex, a platelet receptor for von Willebrand factor (VWF). Most of the mutations identified in the genes encoding for the GP1BA (GPIbα), GP1BB (GPIbβ), and GP9 (GPIX) subunits prevent expression of the complex at the platelet membrane or more rarely its interaction with VWF. As a consequence, platelets are unable to adhere to the vascular subendothelium and agglutinate in response to ristocetin. In order to collect information on BSS patients, we established an International Consortium for the study of BSS, allowing us to enrol and genotype 132 families (56 previously unreported). With 79 additional families for which molecular data were gleaned from the literature, the 211 families characterized so far have mutations in the GP1BA (28%), GP1BB (28%), or GP9 (44%) genes. There is a wide spectrum of mutations with 112 different variants, including 22 novel alterations. Consistent with the rarity of the disease, 85% of the probands carry homozygous mutations with evidence of founder effects in some geographical areas. This overview provides the first global picture of the molecular basis of BSS and will lead to improve patient diagnosis and management.

The American Society of Hematology 2011 evidence-based practice guideline for immune thrombocytopenia

Immune thrombocytopenia (ITP) is commonly encountered in clinical practice. In 1996 the American Society of Hematology published a landmark guidance paper designed to assist clinicians in the management of this disorder. Since 1996 there have been numerous advances in the management of both adult and pediatric ITP. These changes mandated an update in the guidelines. This guideline uses a rigorous, evidence-based approach to the location, interpretation, and presentation of the available evidence. We have endeavored to identify, abstract, and present all available methodologically rigorous data informing the treatment of ITP. We provide evidence-based treatment recommendations using the GRADE system in those areas in which such evidence exists. We do not provide evidence in those areas in which evidence is lacking, or is of lower quality--interested readers are referred to a number of recent, consensus-based recommendations for expert opinion in these clinical areas. Our review identified the need for additional studies in many key areas of the therapy of ITP such as comparative studies of "front-line" therapy for ITP, the management of serious bleeding in patients with ITP, and studies that will provide guidance about which therapy should be used as salvage therapy for patients after failure of a first-line intervention.

Platelet and red blood cell indices in Harris platelet syndrome

Inherited thrombocytopenias, including inherited giant platelet disorders (IGPD) or macro thrombocytopenias are relatively rare, but their prevalence is likely underestimated from complexities of diagnosis and a spectrum of subclinical phenotypes. Harris platelet syndrome (HPS) is the most common IGPD reported from the Indian subcontinent. Of note there are an increased number of hemoglobinopathies reported from the geographic location. We analysed red blood cell and platelet indices of blood donors with HPS from the north eastern part of India and compared them with blood indices of blood donors of south India. We found a statistically significant lower platelet count in blood donors with HPS (median, range) 132 (71-267) vs. 252 (160-478) as compared to donors from south India (P < 0.001). Mean platelet volume (MPV) was higher in donors with HPS 13.1, (range 12-21.9 fl) as compared to donors from south India 7.35 (range 6-9.2 fl) (P < 0.001). This study showed that blood donors with HPS had a low median platelet bio-mass 0.17 (0.10-0.38%) vs. 0.19 (0.13-0.28%) in donors from south India. The platelet distribution width (PDW) was 17.4 (14.9-19.6) in donors with HPS vs. 16.38 (15.2-18.5) in south Indian blood donors (P < 0.001). Thirty-three donors with HPS had a normal platelet count with MPV more than 12 fL. Only donors with HPS had giant platelets and thrombocytopenia on peripheral blood smear examination. None of these donors had Dohle body inclusion in their leukocytes. Compared to donors from south India, donors with HPS had a significantly lower hemoglobin 13.8 (12-16.3 gm/dL) vs. 14.8 (12-18) respectively (P < 0.001) while red distribution width (RDW) was higher in HPS 13.6 (11.5-16.7) vs. 12.8 (11.4-15.1). However we did not find any statistically significant difference in MCV, MCH, MCHC between the two groups. Peripheral blood smear did not show any obvious abnormal red blood cell morphology. In the blood donors with HPS we found a statistically higher MPV, RDW and a lower platelet count and platelet biomass. A population-based study will be helpful in determining the existence of any hemoglobinopathies among subjects with HPS.

Platelet size distinguishes between inherited macrothrombocytopenias and immune thrombocytopenia

BACKGROUND

Distinguishing inherited thrombocytopenias from immune thrombocytopenia (ITP) can be difficult, and patients are therefore at risk of misdiagnosis and inappropriate treatments. Although it is known that the most common inherited forms of thrombocytopenia are characterized by increased platelet size, the diagnostic power of this feature has never been investigated.

OBJECTIVES

The aim of this study was to test the hypothesis that platelet size can be used to differentiate ITP from inherited macrothrombocytopenias.

PATIENTS/METHODS

We measured mean platelet volume (MPV) and mean platelet diameter (MPD), within 2 h of blood sampling, in 35 patients with inherited macrothrombocytopenias [15 MYH9-related disease (MYH9-RD), three biallelic and 17 monoallelic Bernard-Soulier syndrome (BSS)], and 56 with ITP. Using receiving operating characteristic analysis, we searched for the best cut-off values to differentiate between these conditions.

RESULTS

As expected, platelets were larger in inherited macrothrombocytopenias than in ITP. An MPD larger than 3.3 mum differentiated MYH9-RD and BSS from ITP with 0.89 sensitivity and 0.88 specificity, and an MPV larger than 12.4 fL had 0.83 sensitivity and 0.89 specificity. Combining MPD with MPV increased sensitivity and specificity to 0.97 and 0.89, respectively.

CONCLUSION

Platelet size evaluation by both an appropriate cell counter and blood film examination is useful for differentiating inherited macrothrombocytopenias from ITP.

Isolated thrombocytopenia in children: thinking beyond idiopathic thrombocytopenic purpura and leukaemia

The commonest cause of isolated thrombocytopenia in an otherwise well child is idiopathic thrombocytopenic purpura (ITP). The inherited thrombocytopenias such as Bernard-Soulier syndrome are rare but often misdiagnosed as ITP owing to a similar clinical presentation. We describe a child with Bernard-Soulier syndrome who presented with isolated thrombocytopenia, mimicking ITP. Features which help to differentiate these two conditions are discussed with a brief literature review.