Recent advances in the understanding and management of MYH9-related inherited thrombocytopenias

Diagnostic delay of MYH9-related disorder in Japan

MYH9-related disorder (MYH9-RD) is characterized by congenital macrothrombocytopenia and granulocyte inclusion bodies. MYH9-RD is often misdiagnosed as chronic immune thrombocytopenia. In this study, we investigated age at definitive diagnosis and indicative thrombocytopenia in 41 patients with MYH9-RD from the congenital thrombocytopenia registry in Japan. Our cohort comprises 54.8% adults over 18 years at confirmed diagnosis. We found a significant difference (p < 0.0001) between the median age at definitive diagnosis of 25.0 years and for indicative thrombocytopenia it was 9.0 years. Our findings strongly suggest diagnostic delay of MYH9-RD in Japan. Our registry system will continue to contribute to this issue.

Case Report: MYH9-related disease caused by Ala44Pro mutation in a child with a previous diagnosis of chronic immune thrombocytopenia

MYH9-related disease, a rare autosomal dominant platelet disorder characterized by thrombocytopenia, giant platelets, and leukocyte inclusion bodies, may mimic immune thrombocytopenia in children unless suspected and carefully excluded. Here, we present a case involving a three-year-old girl with mild bleeding symptoms since infancy, previously diagnosed with chronic immune thrombocytopenia. The patient exhibited isolated thrombocytopenia and lacked any family history of thrombocytopenia, hearing impairment, or renal failure. Examination of peripheral blood smears via light microscopy revealed significant platelet macrocytosis with giant platelets and basophilic Döhle-like bodies in the neutrophils. Subsequent sequencing analysis of MYH9 gene identified a p.Ala44Pro mutation. Throughout a six-year follow-up period, the patient's condition remained stable. Our report underscores the significance of identifying leukocyte inclusion bodies in peripheral blood smears and considering MYH9-related diseases, even in instances of chronic macrothrombocytopenia devoid of familial history or non-hematological manifestations.

Disease-related non-muscle myosin IIA D1424N rod domain mutation, but not R702C motor domain mutation, disrupts mouse ocular lens fiber cell alignment and hexagonal packing

The mouse ocular lens is an excellent vertebrate model system for studying hexagonal cell packing and shape changes during tissue morphogenesis and differentiation. The lens is composed of two types of cells, epithelial and fiber cells. During the initiation of fiber cell differentiation, lens epithelial cells transform from randomly packed cells to hexagonally shaped and packed cells to form meridional row cells. The meridional row cells further differentiate and elongate into newly formed fiber cells that maintain hexagonal cell shape and ordered packing. In other tissues, actomyosin contractility regulates cell hexagonal packing geometry during epithelial tissue morphogenesis. Here, we use the mouse lens as a model to study the effect of two human disease-related non-muscle myosin IIA (NMIIA) mutations on lens cellular organization during fiber cell morphogenesis and differentiation. We studied genetic knock-in heterozygous mice with NMIIA-R702C motor domain or NMIIA-D1424N rod domain mutations. We observed that while one allele of NMIIA-R702C has no impact on lens meridional row epithelial cell shape and packing, one allele of the NMIIA-D1424N mutation can cause localized defects in cell hexagonal packing. Similarly, one allele of NMIIA-R702C motor domain mutation does not affect lens fiber cell organization while the NMIIA-D1424N mutant proteins disrupt fiber cell organization and packing. Our work demonstrates that disease-related NMIIA rod domain mutations (D1424N or E1841K) disrupt mouse lens fiber cell morphogenesis and differentiation.

Nonmuscle Myosin IIA Regulates the Precise Alignment of Hexagonal Eye Lens Epithelial Cells During Fiber Cell Formation and Differentiation

Purpose

Epithelial cells in the equatorial region of the ocular lens undergo a remarkable transition from randomly packed cells into precisely aligned and hexagon-shaped cells organized into meridional rows. We investigated the function of nonmuscle myosin IIA (encoded by Myh9) in regulating equatorial epithelial cell alignment to form meridional rows during secondary fiber cell morphogenesis.

Methods

We used genetic knock-in mice to study a common human Myh9 mutation, E1841K, in the rod domain. The E1841K mutation disrupts bipolar filament assembly. Lens shape, clarity, and stiffness were evaluated, and Western blots were used to determine the level of normal and mutant myosins. Cryosections and lens whole mounts were stained and imaged by confocal microscopy to investigate cell shape and organization.

Results

We observed no obvious changes in lens size, shape, and biomechanical properties (stiffness and resilience) between the control and nonmuscle myosin IIA-E1841K mutant mice at 2 months of age. Surprisingly, we found misalignment and disorder of fiber cells in heterozygous and homozygous mutant lenses. Further analysis revealed misshapen equatorial epithelial cells that cause disorientation of the meridional rows before fiber cell differentiation in homozygous mutant lenses.

Conclusions

Our data indicate that nonmuscle myosin IIA bipolar filament assembly is required for the precise alignment of the meridional rows at the lens equator and that the organization of lens fiber cells depends on the proper patterning of meridional row epithelial cells. These data also suggest that lens fiber cell organization and a hexagonal shape are not required for normal lens size, shape transparency, or biomechanical properties.

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.

Overlapping Machinery in Lysosome-Related Organelle Trafficking: A Lesson from Rare Multisystem Disorders

Lysosome-related organelles (LROs) are a group of functionally diverse, cell type-specific compartments. LROs include melanosomes, alpha and dense granules, lytic granules, lamellar bodies and other compartments with distinct morphologies and functions allowing specialised and unique functions of their host cells. The formation, maturation and secretion of specific LROs are compromised in a number of hereditary rare multisystem disorders, including Hermansky-Pudlak syndromes, Griscelli syndrome and the Arthrogryposis, Renal dysfunction and Cholestasis syndrome. Each of these disorders impacts the function of several LROs, resulting in a variety of clinical features affecting systems such as immunity, neurophysiology and pigmentation. This has demonstrated the close relationship between LROs and led to the identification of conserved components required for LRO biogenesis and function. Here, we discuss aspects of this conserved machinery among LROs in relation to the heritable multisystem disorders they associate with, and present our current understanding of how dysfunctions in the proteins affected in the disease impact the formation, motility and ultimate secretion of LROs. Moreover, we have analysed the expression of the members of the CHEVI complex affected in Arthrogryposis, Renal dysfunction and Cholestasis syndrome, in different cell types, by collecting single cell RNA expression data from the human protein atlas. We propose a hypothesis describing how transcriptional regulation could constitute a mechanism that regulates the pleiotropic functions of proteins and their interacting partners in different LROs.

Defective VWF secretion due to the expression of MYH9-RD E1841K mutant in endothelial cells disrupts hemostasis

Mutations in MYH9, the gene encoding the heavy chain of non-muscle myosin IIa (NMII-A), cause MYH9-related disease (MYH9-RD) that is an autosomal-dominant thrombocytopenia with bleeding tendency. Previously, we showed that NMII-A in endothelial cells (ECs) is critical for hemostasis via regulating von Willebrand factor (VWF) release from Weibel-Palade bodies (WPBs). The aim of this study was to determine the role of the expression of MYH9 mutants in ECs in the pathogenesis of the MYH9-RD bleeding symptom. First, we expressed the 5 most common NMII-A mutants in ECs, and found that E1841K mutant-expressing ECs secreted less VWF than the controls in response to a cAMP signaling agonist. Then, we generated 2 knockin mouse lines, one with Myh9 E1841K in ECs and the other in megakaryocytes. Endothelium-specific E1841K mice exhibited impaired cAMP-induced VWF release and a prolonged bleeding time with normal platelets, while megakaryocyte-specific E1841K mice exhibited macrothrombocytopenia and a prolonged bleeding time with normal VWF release. Finally, we present mechanistic findings that E1841K mutation not only interferes with S1943 phosphorylation and impairs the peripheral distribution of Rab27a positive WPBs in ECs under quiescent condition, but also interferes with S1916 phosphorylation by disrupting the interaction with zyxin and CKIIα, and reduces actin framework formation around WPBs and subsequent VWF secretion under the stimulation by a cAMP agonist. Altogether, our results suggest that impaired cAMP-induced endothelial VWF secretion by E1841K mutant expression may contribute to the MYH9-RD bleeding phenotype.

Reduced platelet forces underlie impaired hemostasis in mouse models of MYH9-related disease

MYH9-related disease patients with mutations in the contractile protein nonmuscle myosin heavy chain IIA display, among others, macrothrombocytopenia and a mild-to-moderate bleeding tendency. In this study, we used three mouse lines, each with one point mutation in the Myh9 gene at positions 702, 1424, or 1841, to investigate mechanisms underlying the increased bleeding risk. Agonist-induced activation of Myh9 mutant platelets was comparable to controls. However, myosin light chain phosphorylation after activation was reduced in mutant platelets, which displayed altered biophysical characteristics and generated lower adhesion, interaction, and traction forces. Treatment with tranexamic acid restored clot retraction in the presence of tPA and reduced bleeding. We verified our findings from the mutant mice with platelets from patients with the respective mutation. These data suggest that reduced platelet forces lead to an increased bleeding tendency in patients with MYH9-related disease, and treatment with tranexamic acid can improve the hemostatic function.

Diagnosis of rare bleeding disorders

Rare bleeding disorders result in significant morbidity but are globally underdiagnosed. Advances in genomic testing and specialist laboratory assays have greatly increased the diagnostic armamentarium. This has resulted in the discovery of new genetic causes for rare diseases and a better understanding of the underlying molecular pathology.

Individualized Bleeding Risk Assessment through Thromboelastography: A Case Report of May-Hegglin Anomaly in Preterm Twin Neonates

May–Hegglin anomaly (MHA) is a rare autosomal dominant disorder in the spectrum of myosin heavy chain-related disorders (MYH9-RD), characterized by congenital macrothrombocytopenia and white blood cell inclusions. MHA carries a potential risk of hemorrhagic complications. Bleeding diathesis is usually mild, but sporadic, life-threatening events have been reported. Data regarding the clinical course and outcomes of neonatal MYH9-RD are limited, and specific guidelines on platelet transfusion in asymptomatic patients are lacking. We present monochorionic twins born preterm at 32 weeks of gestation to an MHA mother; both presented with severe thrombocytopenia at birth. Peripheral blood smear demonstrated the presence of macrothrombocytes, and immunofluorescence confirmed the diagnosis of MHA. Close clinical monitoring excluded bleeding complications, and serial hemostatic assessments through a viscoelastic system demonstrated functionally normal primary hemostasis in both patients. Therefore, prophylactic platelet transfusions were avoided. Whole DNA sequencing confirmed the pathogenetic variant of MHA of maternal origin in both twins. Thromboelastography allowed real-time bedside bleeding risk assessment and supported individualized transfusion management in preterm newborns at risk of hemostatic impairment. This report suggests that dynamic and appropriate clotting monitoring may contribute to the more rational use of platelets’ transfusions while preserving patients with hemorrhagic complications and potential transfusion-related side effects.

Anesthetic Management of Living-Donor Renal Transplantation in a Patient With Epstein Syndrome Using Rotational Thromboelastometry: A Case Report

Epstein syndrome is a myosin heavy chain 9 (MYH9)-related disorder characterized by hearing loss and macrothrombocytopenia with renal failure, which usually requires platelet transfusion during surgery. We report the case of a 22-year-old man who underwent living-donor renal transplantation without platelet transfusion using rotational thromboelastometry (ROTEM) monitoring. His intraoperative laboratory coagulation findings were a platelet count of 28–31 × 10⁹/L based on microscopy and fibrinogen of 256 mg/dL. However, his extrinsic pathway evaluations by ROTEM were normal. The estimated blood loss during the operation was 150 mL, and the patient showed no bleeding complications without platelet transfusion.

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.

Rare inherited kidney diseases: an evolving field in Nephrology

There are more than 150 different rare genetic kidney diseases. They can be classified according to diagnostic findings as (i) disorders of growth and structure, (ii) glomerular diseases, (iii) tubular, and (iv) metabolic diseases. In recent years, there has been a shift of paradigm in this field. Molecular testing has become more accessible, our understanding of the underlying pathophysiologic mechanisms of these diseases has evolved, and new therapeutic strategies have become more available. Therefore, the role of nephrologists has progressively shifted from a mere spectator to an active player, part of a multidisciplinary team in the diagnosis and treatment of these disorders. This article provides an overview of the recent advances in rare hereditary kidney disorders by discussing the genetic aspects, clinical manifestations, diagnostic, and therapeutic approaches of some of these disorders, named familial focal and segmental glomerulosclerosis, tuberous sclerosis complex, Fabry nephropathy, and MYH-9 related disorder.

Spontaneous and recurrent subdural haematoma in a patient with May-Hegglin anomaly

Both acute and chronic subdural haematomas typically occur following trauma. Non-traumatic causes are less common, but aetiologies include arteriovenous malformation, intracranial aneurysm rupture, tumour-associated haemorrhage and coagulopathies. May-Hegglin anomaly is an example of a coagulopathy, which is caused by a mutation in the gene encoding non-muscle myosin heavy chain 9 (MYH9) and therefore falls into a group of diseases referred to as MYH9-related diseases (MYH9-RD). The symptomology of MYH9-RD is often mild, and patients tend to experience epistaxis, gingival bleeding and bruising. Life-threatening haemorrhage rarely occurs. In this short report, we describe a patient with known May-Hegglin anomaly who presented with a potentially life-threatening, spontaneous subdural haematoma requiring surgery on two occasions. This is only the second such report in the literature, and the first of spontaneous and recurrent haemorrhage in association with May-Hegglin anomaly.

Update on diagnosis and treatment of immune thrombocytopenia

BACKGROUND

Immune thrombocytopenia (ITP) is a heterogeneous acquired disorder characterized by isolated thrombocytopenia whose exact pathogenesis is not yet clear. Depending upon the presence or absence of an underlying treatable cause, ITP can be categorized as primary or secondary. Primary ITP is a diagnosis of exclusion and there is no gold standard test for its confirmation. Recent drug intake, infections, lymphoproliferative disorders, and connective tissue disorders should be ruled out before labeling a patient as primary ITP.

AREA COVERED

This review summarizes a comprehensive update on the diagnostic and therapeutic modalities for ITP. We reviewed the literature using GOOGLE SCHOLAR, PUBMED and ClinicalTrial.gov databases as needed to support the evidence. We searched the literature using the following keywords: 'immune thrombocytopenia,' 'idiopathic thrombocytopenic purpura,' 'thrombocytopenia,' 'immune thrombocytopenic purpura,' and 'isolated thrombocytopenia'.

EXPERT OPINION

We believe that more detailed studies are required to understand the exact pathophysiology behind ITP. The first-line drugs like corticosteroids have both short-term and long-term adverse effects. This brings the need to explore effective alternative medications and to reconsider their role in ITP treatment algorithm if guidelines can be modified based on new studies.

Renal Biopsy-induced Hematoma and Infection in a Patient with Asymptomatic May-Hegglin Anomaly

The May-Hegglin anomaly is characterized by inherited thrombocytopenia, giant platelets, and leukocyte cytoplasmic inclusion bodies. The Fechtner, Sebastian, and Epstein syndromes are associated with mutations of the MYH9-coding nonmuscle myosin heavy chain ⅡA, similar to the May-Hegglin anomaly, and are together classified as MYH9 disorders. MYH9 disorders may include symptoms of Alport syndrome, including nephritis and auditory and ocular disorders. A 6-year-old boy was diagnosed with an MYH9 disorder after incidental discovery of hematuria and proteinuria. Focal segmental glomerulosclerosis was detected on renal biopsy. However, despite no prior bleeding diatheses, he developed a large post-biopsy hematoma despite a preprocedural platelet transfusion calculated to increase the platelet count from 54,000/μL to >150,000/μL. Idiopathic thrombocytopenic purpura is a major cause of pediatric thrombocytopenia following acute infection or vaccination, and patients with MYH9 disorders may be misdiagnosed with idiopathic thrombocytopenic purpura and inappropriately treated with corticosteroids. Careful differential diagnosis is important in thrombocytopenic patients with hematuria and proteinuria for the early detection of thrombocytopenia. Patients with MYH9 disorders require close follow-up and treatment with angiotensin Ⅱ receptor blockers to prevent the onset of progressive nephritis, which may necessitate hemodialysis or renal transplantation. The need for renal biopsy in patients with MYH9 disorders should be carefully considered because there could be adverse outcomes even after platelet transfusion.

Genomic Analysis for the Detection of Bleeding and Thrombotic Disorders

The development of high-throughput sequencing technologies has ushered in a new era of genomic testing in clinical medicine. This has greatly enhanced our diagnostic repertoire for hemostatic diseases particularly for milder or rarer bleeding disorders. New genetic causes for heritable platelet disorders have been discovered along with the recognition of clinical manifestations outside hemostasis, such as the association of leukemia with RUNX1 variation. Genome-wide association studies in heritable thrombophilia have demonstrated that some of the genetic variants that are commonly included in thrombophilia testing are of no clinical relevance, while uncovering new variants that should potentially be included. The implementation of new technology has necessitated far-reaching changes in clinical practice to deal with incidental findings, variants of uncertain significance, and genetic disease modifiers. Mild bleeding disorders that were previously considered to have a monogenic basis now appear to have an oligogenic etiology. To harness these advances in knowledge large databases have been developed to capture the new genomic information with phenotypic features on a population-wide scale. The use of this so-called "big data" requires new bioinformatics tools with the promise of delivering precision medicine in the foreseeable future. This review discusses the use of these technologies in clinical practice, the benefits of genomic testing, and some of the challenges associated with implementation.

A De Novo Mutation in MYH9 in a Child With Severe and Prolonged Macrothrombocytopenia

Congenital macrothrombocytopenia is a diverse group of hereditary disorders caused by mutations in the MYH9 gene, which encodes the nonmuscle myosin heavy chain-A, an important motor protein in hemopoietic cells. Thus, the term MYH9-related disease has been proposed, but the clinicopathologic basis of MYH9 mutations has been poorly investigated. Here, we report a sporadic case of Epstein syndrome, an MYH9 disorder, in a 4-year-old Chinese boy who presented with macrothrombocytopenia. He had no family history of thrombocytopenia, hearing loss, or renal failure. A de novo heterozygous MYH9 mutation, c.287C>T; p. (Ser96Leu), was found in this patient. Genotype-phenotype analysis of all reported mutations suggested a domain-specific relationship between the location of the MYH9 mutation and the penetrance of the nonhematologic characteristics of MYH9-related disorders. Our study highlights the importance of suspecting MYH9-related disease even in cases of chronic macrothrombocytopenia without a family history or extrahematologic symptoms.

Aminated Fullerene Abrogates Cancer Cell Migration by Directly Targeting Myosin Heavy Chain 9

Functional fullerene derivatives exhibit fantastic inhibitory capabilities against cancer survival and metastasis, but the absence of clarified biological molecular targets and ambiguous regulation mechanisms set barriers for their clinical transformation. Cancer metastasis is the primary cause of mortality and initiated with increased cell migration, making cell motility regulation a high-value therapeutic target in precision medicine. Herein, a critical molecular target of the aminated fullerene derivative (C₇₀-EDA), myosin heavy chain 9 (MYH9), was initially identified by a pull-down assay and MS screening. MYH9 is a cytoplasm-located protein and is responsible for cell motility and epithelial-mesenchymal transition regulation. Omics data from large-scale clinical samples reveals that MYH9 gets overexpressed in various cancers and correlates with unfavorable prognosis, indicating that it is a potential antineoplastic target. It is unveiled that C₇₀-EDA binds to the C-terminal of MYH9, triggering the transport of MYH9 from the cytoplasm to the cell edge, blocking the MYH9-involved cell mobility, and inhibiting the metastasis-associated EMT process. This work provides a precise biological target and new strategies for fullerene applications in cancer therapy.

Inherited thrombocytopenias: an updated guide for clinicians

The great advances in the knowledge of inherited thrombocytopenias (ITs) made since the turn of the century have significantly changed our view of these conditions. To date, ITs encompass 45 disorders with different degrees of complexity of the clinical picture and very wide variability in the prognosis. They include forms characterized by thrombocytopenia alone, forms that present with other congenital defects, and conditions that predispose to acquire additional diseases over the course of life. In this review, we recapitulate the clinical features of ITs with emphasis on the forms predisposing to additional diseases. We then discuss the key issues for a rational approach to the diagnosis of ITs in clinical practice. Finally, we aim to provide an updated and comprehensive guide to the treatment of ITs, including the management of hemostatic challenges, the treatment of severe forms, and the approach to the manifestations that add to thrombocytopenia.

Moyamoya-like vasculopathy associated to MYH9-related thrombocytopenia manifested by multiple cerebral ischemic lesions: a case report

Background

Moyamoya-like vasculopathy (MMV) and myosin heavy chain 9-related platelet disorders (MYH9-RPDs) or macrothrombocitopenias are rare syndromes. Their association is even more infrequent.

Case presentation

A 29-year-old female with history of MYH9-RPD, presented to our department for episodes suggesting transient ischemic attacks. Based on the imaging studies that revealed multiple ischemic lesions and stenoses of both distal internal carotid arteries and the arteries of the circle of Willis, the diagnosis of MMV was established. The treatment with Verapamil was initiated, leading to symptom remission. Two months later, the patient presented one episode of dysarthria, followed by involuntary movements of the right upper limb, few days later. Long-term electroencephalogram monitoring depicted epileptiform abnormalities. Resolution of symptoms was obtained after increasing the dose of Verapamil, and initiating Levetiracetam.

Conclusions

This is an interesting case of a patient with two rare pathologies, who presented with cerebral ischemic strokes. To our knowledge there are few cases described in the literature presenting with cerebral hemorrhagic events but none of them with multiple cerebral ischemic lesions. As these cases are very rare, it is important to gather evidence regarding the best approach and treatment strategy.

Inherited Platelet Disorders: Diagnosis and Management

Inherited platelet disorders are rare but they can have considerable clinical impacts, and studies of their causes have advanced understanding of platelet formation and function. Effective hemostasis requires adequate circulating numbers of functional platelets. Quantitative, qualitative and combined platelet disorders with a bleeding phenotype have been linked to defects in platelet cytoskeletal elements, cell surface receptors, signal transduction pathways, secretory granules and other aspects. Inherited platelet disorders have variable clinical presentations, and diagnosis and management is often challenging. Evaluation begins with detailed patient and family histories, including a bleeding score. The physical exam identifies potential syndromic features of inherited platelet disorders and rules out other causes. Laboratory investigations include a complete blood count, blood film, coagulation testing and Von Willebrand factor assessment. A suspected platelet function disorder is further assessed by platelet aggregation, flow cytometry, platelet dense granule release and/or content, and genetic testing. The management of platelet function disorders aims to minimize the risk of bleeding and achieve adequate hemostasis when needed. Although not universal, platelet transfusion remains a crucial component in the management of many inherited platelet disorders.

Neurological disorder-associated genetic variants in individuals with psychogenic nonepileptic seizures

Psychogenic nonepileptic seizures (PNES) are diagnosed in approximately 30% of patients referred to tertiary care epilepsy centers. Little is known about the molecular pathology of PNES, much less about possible underlying genetic factors. We generated whole-exome sequencing and whole-genome genotyping data to identify rare, pathogenic (P) or likely pathogenic (LP) variants in 102 individuals with PNES and 448 individuals with focal (FE) or generalized (GE) epilepsy. Variants were classified for all individuals based on the ACMG-AMP 2015 guidelines. For research purposes only, we considered genes associated with neurological or psychiatric disorders as candidate genes for PNES. We observe in this first genetic investigation of PNES that six (5.88%) individuals with PNES without coexistent epilepsy carry P/LP variants (deletions at 10q11.22-q11.23, 10q23.1-q23.2, distal 16p11.2, and 17p13.3, and nonsynonymous variants in NSD1 and GABRA5). Notably, the burden of P/LP variants among the individuals with PNES was similar and not significantly different to the burden observed in the individuals with FE (3.05%) or GE (1.82%) (PNES vs. FE vs. GE (3 × 2 χ2), P = 0.30; PNES vs. epilepsy (2 × 2 χ2), P = 0.14). The presence of variants in genes associated with monogenic forms of neurological and psychiatric disorders in individuals with PNES shows that genetic factors are likely to play a role in PNES or its comorbidities in a subset of individuals. Future large-scale genetic research studies are needed to further corroborate these interesting findings in PNES.

A family with an MYH9-related disorder with different phenotypes masquerading as immune thrombocytopaenia: an underreported disorder in Taiwan

A 66-year-old woman had experienced abnormal bleeding since the age of 7. Thrombocytopenia was not detected until she was 48, and immune thrombocytopenia was diagnosed at age 66. She also reported experiencing hearing disturbance since the age of 30 and acute renal failure since the age of 61 but reported no visual disturbance. Her younger son, who was 40 years old, also experienced abnormal bleeding since the age of 6, but immune thrombocytopenia was diagnosed as late as age 35. He had no other associated disorders. Laboratory examinations of both mother and son revealed a low platelet count (8000 and 29,000 µL, respectively), giant platelets and Döhle body-like granulocyte inclusion bodies. The mother had a high creatinine level (15.4 mg/dL) and normal liver enzyme levels. MYH9 genetic analysis identified a heterozygous mutation, c.101T>A, p.Val34Glu at exon 2 in both patients. These clinical and laboratory findings were consistent with a diagnosis of an MYH9-related disorder with different phenotypes observed in the same family. MYH9-related disorders were recognised in 2003, but were often misdiagnosed as immune thrombocytopenia, and hence, they have rarely been reported in Taiwan.

Interplay between platelets and coagulation

Haemostasis stops bleeding at the site of vascular injury and maintains the integrity of blood vessels through clot formation. This regulated physiological process consists of complex interactions between endothelial cells, platelets, von Willebrand factor and coagulation factors. Haemostasis is initiated by a damaged vessel wall, followed with a rapid adhesion, activation and aggregation of platelets to the exposed subendothelial extracellular matrix. At the same time, coagulation factors aggregate on the procoagulant surface of activated platelets to consolidate the platelet plug by forming a mesh of cross-linked fibrin. Platelets and coagulation mutually influence each other and there are strong indications that, thanks to the interplay between platelets and coagulation, haemostasis is far more effective than the two processes separately. Clinically this is relevant because impaired interaction between platelets and coagulation may result in bleeding complications, while excessive platelet-coagulation interaction induces a high thrombotic risk. In this review, platelets, coagulation factors and the complex interaction between them will be discussed in detail.

Diagnosis of rare bleeding disorders

Rare bleeding disorders result in significant morbidity but are globally underdiagnosed. Advances in genomic testing and specialist laboratory assays have greatly increased the diagnostic armamentarium. This has resulted in the discovery of new genetic causes for rare diseases and a better understanding of the underlying molecular pathology.

Nuclear MYH9-induced CTNNB1 transcription, targeted by staurosporin, promotes gastric cancer cell anoikis resistance and metastasis

Rationale: Peritoneal metastasis predicts poor prognosis of gastric cancer (GC) patients, and the underlying mechanisms are poorly understood. Methods: The 2-DIGE, MALDI-TOF/TOF MS and single-cell transcriptome were used to detect differentially expressed proteins among normal gastric mucosa, primary GC and peritoneal metastatic tissues. Lentiviruses carrying shRNA and transcription activator-like effector nuclease technology were used to knock down myosin heavy chain 9 (MYH9) expression in GC cell lines. Immunofluorescence, immune transmission electron microscopy, chromatin fractionation, co-immunoprecipitation, and assays for chromatin immunoprecipitation, dual luciferase reporter, agarose-oligonucleotide pull-down, flow cytometry and cell anoikis were performed to uncover nuclear MYH9-induced β-catenin (CTNNB1) transcription in vitro. Nude mice and conditional transgenic mice were used to investigate the findings in vivo. Results: We observed that MYH9 was upregulated in metastatic GC tissues and was associated with a poor prognosis of GC patients. Mechanistically, we confirmed that MYH9 was mainly localized in the GC cell nuclei by four potential nuclear localization signals. Nuclear MYH9 bound to the CTNNB1 promoter through its DNA-binding domain, and interacted with myosin light chain 9, β-actin and RNA polymerase II to promote CTNNB1 transcription, which conferred resistance to anoikis in GC cells in vitro and in vivo. Staurosporine reduced nuclear MYH9 S1943 phosphorylation to inhibit CTNNB1 transcription, Wnt/β-catenin signaling activation and GC progression in both orthotropic xenograft GC nude mouse and transgenic GC mouse models. Conclusion: This study identified that nuclear MYH9-induced CTNNB1 expression promotes GC metastasis, which could be inhibited by staurosporine, indicating a novel therapy for GC peritoneal metastasis.

Linking the Landscape of MYH9-Related Diseases to the Molecular Mechanisms that Control Non-Muscle Myosin II-A Function in Cells

The MYH9 gene encodes the heavy chain (MHCII) of non-muscle myosin II A (NMII-A). This is an actin-binding molecular motor essential for development that participates in many crucial cellular processes such as adhesion, cell migration, cytokinesis and polarization, maintenance of cell shape and signal transduction. Several types of mutations in the MYH9 gene cause an array of autosomal dominant disorders, globally known as MYH9-related diseases (MYH9-RD). These include May-Hegglin anomaly (MHA), Epstein syndrome (EPS), Fechtner syndrome (FTS) and Sebastian platelet syndrome (SPS). Although caused by different MYH9 mutations, all patients present macrothrombocytopenia, but may later display other pathologies, including loss of hearing, renal failure and presenile cataracts. The correlation between the molecular and cellular effects of the different mutations and clinical presentation are beginning to be established. In this review, we correlate the defects that MYH9 mutations cause at a molecular and cellular level (for example, deficient filament formation, altered ATPase activity or actin-binding) with the clinical presentation of the syndromes in human patients. We address why these syndromes are tissue restricted, and the existence of possible compensatory mechanisms, including residual activity of mutant NMII-A and/ or the formation of heteropolymers or co-polymers with other NMII isoforms.

Familial macro thrombocytopenia: role of genetics where morphology fails

: Myosin heavy chain 9 (MYH9)-related disorders are rare inherited platelet disorders that are accompanied by a wide variety of systemic abnormalities. The persistent thrombocytopenia is usually asymptomatic and these patients are often misdiagnosed and treated as immune thrombocytopenia. MYH9 gene has been studied in association with solid organ malignancies. We report a young girl with family history of thrombocytopenia and hearing loss who presented with kidney dysfunction and later developed acute lymphoblastic leukemia. She lacked the characteristic inclusion bodies in her blood granulocytes, however a diagnosis of MYH9-related Epstein syndrome was confirmed on genetic testing. In the background of known causal association of MYH9 gene in solid organ malignancies, the role of MYH9 gene variant in malignant transformation in the index case remains conjectural.

Idiopathic thrombocytopenic purpura (ITP) - new era for an old disease

Immune thrombocytopenia is an autoimmune hematological disorder characterized by severely decreased platelet count of peripheral cause: platelet destruction via antiplatelet antibodies which may also affect marrow megakaryocytes. Patients may present in critical situations, with cutaneous and/or mucous bleeding and possibly life-threatening organ hemorrhages (cerebral, digestive, etc.) Therefore, rapid diagnosis and therapeutic intervention are mandatory. Corticotherapy represents the first treatment option, but as in any autoimmune disorder, there is a high risk of relapse. Second line therapy options include: intravenous immunoglobulins, thrombopoietin receptor agonists, rituximab or immunosuppression, but their benefit is usually temporary. Moreover, the disease generally affects young people who need repeated and prolonged treatment and hospitalization and therefore, it is preferred to choose a long term effect therapy. Splenectomy - removal of the site of platelet destruction - represents an effective and stable treatment, with 70-80% response rate and low complications incidence. A challenging situation is the association of ITP with pregnancy, which further increases the risk due to the immunodeficiency of pregnancy, major dangers of bleeding, vital risks for mother and fetus, potential risks of medication, necessity of prompt intervention in the setting of specific obstetrical situations - delivery, pregnancy loss, obstetrical complications, etc. We present an updated review of the current clinical and laboratory data, as well as a detailed analysis of the available therapeutic options with their benefits and risks, and also particular associations (pregnancy, relapsed and refractory disease, emergency treatment).

A case report of optic neuropathy following dacryocystorhinostomy in a 57-year-old female patient with May-Hegglin anomaly

Background

We report a rare case of optic neuropathy following dacryocystorhinostomy (DCR) in a 57-year-old female patient with May-Hegglin anomaly.

Case presentation

The patient was presented with sudden onset of vision loss for the left eye after DCR under general anesthesia. Her best corrected visual acuity was light perception in the left eye. Relative afferent pupillary defect was detected in her left eye. Magnetic resonance imaging of the orbit revealed an hyperintensity at the intra-orbital segment of the left optic nerve on T2-weighted image and Flair image. The patient was diagnosed with acute postoperative optic neuropathy and treated with methylprednisolone. Although her vision partially improved, she was left with a visual field defect in the left eye.

Conclusions

In patients with hematologic diseases, postoperative vision loss can occur following even minor surgery under general anesthesia, such as DCR. Therefore, preoperative counseling regarding the risk of visual loss should be given to high-risk patients.

The Myosin Family of Mechanoenzymes: From Mechanisms to Therapeutic Approaches

Myosins are among the most fascinating enzymes in biology. As extremely allosteric chemomechanical molecular machines, myosins are involved in myriad pivotal cellular functions and are frequently sites of mutations leading to disease phenotypes. Human β-cardiac myosin has proved to be an excellent target for small-molecule therapeutics for heart muscle diseases, and, as we describe here, other myosin family members are likely to be potentially unique targets for treating other diseases as well. The first part of this review focuses on how myosins convert the chemical energy of ATP hydrolysis into mechanical movement, followed by a description of existing therapeutic approaches to target human β-cardiac myosin. The next section focuses on the possibility of targeting nonmuscle members of the human myosin family for several diseases. We end the review by describing the roles of myosin in parasites and the therapeutic potential of targeting them to block parasitic invasion of their hosts.

Diagnosis of Inherited Platelet Disorders on a Blood Smear

Inherited platelet disorders (IPDs) are rare diseases featured by low platelet count and defective platelet function. Patients have variable bleeding diathesis and sometimes additional features that can be congenital or acquired. Identification of an IPD is desirable to avoid misdiagnosis of immune thrombocytopenia and the use of improper treatments. Diagnostic tools include platelet function studies and genetic testing. The latter can be challenging as the correlation of its outcomes with phenotype is not easy. The immune-morphological evaluation of blood smears (by light- and immunofluorescence microscopy) represents a reliable method to phenotype subjects with suspected IPD. It is relatively cheap, not excessively time-consuming and applicable to shipped samples. In some forms, it can provide a diagnosis by itself, as for MYH9-RD, or in addition to other first-line tests as aggregometry or flow cytometry. In regard to genetic testing, it can guide specific sequencing. Since only minimal amounts of blood are needed for the preparation of blood smears, it can be used to characterize thrombocytopenia in pediatric patients and even newborns further. In principle, it is based on visualizing alterations in the distribution of proteins, which result from specific genetic mutations by using monoclonal antibodies. It can be applied to identify deficiencies in membrane proteins, disturbed distribution of cytoskeletal proteins, and alpha as well as delta granules. On the other hand, mutations associated with impaired signal transduction are difficult to identify by immunofluorescence of blood smears. This review summarizes technical aspects and the main diagnostic patterns achievable by this method.

A novel de novo MYH9 mutation in MYH9-related disease: A case report and review of literature

INTRODUCTION

MYH9-related disease (MYH9-RD) is a rare autosomal dominant disorder caused by mutations in MYH9, which is responsible for encoding nonmuscle myosin heavy chains IIA (NMMHCIIA). MYH9-RD is clinically characterized by congenital macrothrombocytopenia, granulocyte inclusions variably associated with the risk of developing progressive sensorineural deafness, cataracts and nephropathy.

PATIENT CONCERNS

A 5-year-old boy had a history of a mild bleeding tendency and chronic thrombocytopenia, first identified at four months of age. No other family members were noted to have similar clinical features or hematologic disorders.

DIAGNOSES

The boy was diagnosed with MYH9-RD. Light microscopic examination of peripheral blood films (Wright-Giemsa stain) showed marked platelet macrocytosis with giant platelets and basophilic Döhle-like inclusions in 83% of the neutrophils. Immunofluorescence analysis disclosed a type II pattern, manifested by neutrophils which contained several circle-to-oval shaped cytoplasmic NMMMHCA-positive granules. Sequencing analysis of MYH9-RD genes was carried out and revealed a novel missense mutation of c.97T>G (p.W33G) in the patient but not in his parents.

INTERVENTION

No treatment is necessary. Recognition of MYH9-RD is important to Avoiding unnecessary and potentially harmful treatments.

OUTCOMES

The patient's condition remained stable during the follow-up.

CONCLUSIONS

As a result of identifying this missense mutation in this particular case, we have added c.97T>G (p.W33G) to the broad spectrum of potential MYH9 mutations.

The use of pan-retinal photocoagulation to treat recurrent vitreous haemorrhage with neovascularisation in the context of Epstein syndrome: an MYH9-related disorder

A female patient presented with stable chronic thrombocytopaenia with large platelets, sensorineuronal deafness and renal impairment. Her treatment was refractory to intravenous immunoglobulins (IVIG) and steroids for a putative diagnosis of immune thrombocytopaenic purpura (ITP). She underwent genetic testing which revealed a MYH9 mutation in-keeping with a diagnosis of Epstein Syndrome. Subsequently to this she developed globally constricted fields on Goldmann visual field testing. MRI pituitary was unremarkable but she was diagnosed with a pituitary microprolactinoma secondary to raised prolactin in the blood responsive to carbegoline therapy. She subsequently developed retinal haemorrhages and recurrent vitreous haemorrhages due to neovascularisation. Fluorescein angiography revealed the extent of the neovascularisation and microvascular ischaemia. She underwent pan-retinal photocoagulation (PRP) to treat the ischaemic stimulus which resulted in regression of the new vessels and cessation of vitreous haemorrhages. There are no previous reported cases of microvascular retinal disease in the literature in the context of Epstein Syndrome, and this is the first report of successful treatment with PRP.

Renin-angiotensin System Blockade Therapy for Early Renal Involvement in MYH9-related Disease with an E1841K Mutation

MYH9-related disease is a rare genetic disorder characterized by macrothrombocytopenia, with frequent proteinuric nephropathy, hearing loss, and cataract. Although proteinuric nephropathy usually progresses to renal failure, there is no established treatment for the nephropathy. We herein describe the case of a 19-year-old man carrying an E1841K MYH9 mutation, who developed persistent proteinuria. The patient was diagnosed with early-stage MYH9-related nephropathy based on the histological examination of a kidney biopsy specimen. The patient was treated with enalapril, which significantly reduced the proteinuria with no decline in his renal function. The early administration of renin-angiotensin system blockade therapy may have beneficial effects on MYH9-related nephropathy in patients with E1841K mutations. We also briefly summarize previously published cases of MYH9-related nephropathy treated with renin-angiotensin system (RAS) blockade therapy.

Next-generation sequencing for the diagnosis of MYH9-RD: Predicting pathogenic variants

The heterogeneous manifestations of MYH9‐related disorder (MYH9‐RD), characterized by macrothrombocytopenia, Döhle‐like inclusion bodies in leukocytes, bleeding of variable severity with, in some cases, ear, eye, kidney, and liver involvement, make the diagnosis for these patients still challenging in clinical practice. We collected phenotypic data and analyzed the genetic variants in more than 3,000 patients with a bleeding or platelet disorder. Patients were enrolled in the BRIDGE‐BPD and ThromboGenomics Projects and their samples processed by high throughput sequencing (HTS). We identified 50 patients with a rare variant in MYH9. All patients had macrothrombocytes and all except two had thrombocytopenia. Some degree of bleeding diathesis was reported in 41 of the 50 patients. Eleven patients presented hearing impairment, three renal failure and two elevated liver enzymes. Among the 28 rare variants identified in MYH9, 12 were novel. HTS was instrumental in diagnosing 23 patients (46%). Our results confirm the clinical heterogeneity of MYH9‐RD and show that, in the presence of an unclassified platelet disorder with macrothrombocytes, MYH9‐RD should always be considered. A HTS‐based strategy is a reliable method to reach a conclusive diagnosis of MYH9‐RD in clinical practice.

Inherited Thrombocytopenia: Update on Genes and Genetic Variants Which may be Associated With Bleeding

Inherited thrombocytopenia (IT) is comprised of a group of hereditary disorders characterized by a reduced platelet count as the main feature, and often with abnormal platelet function, which can subsequently lead to impaired haemostasis. Inherited thrombocytopenia results from genetic mutations in genes implicated in megakaryocyte differentiation and/or platelet formation and clearance. The identification of the underlying causative gene of IT is challenging given the high degree of heterogeneity, but important due to the presence of various clinical presentations and prognosis, where some defects can lead to hematological malignancies. Traditional platelet function tests, clinical manifestations, and hematological parameters allow for an initial diagnosis. However, employing Next-Generation Sequencing (NGS), such as Whole Genome and Whole Exome Sequencing (WES) can be an efficient method for discovering causal genetic variants in both known and novel genes not previously implicated in IT. To date, 40 genes and their mutations have been implicated to cause many different forms of inherited thrombocytopenia. Nevertheless, despite this advancement in the diagnosis of IT, the molecular mechanism underlying IT in some patients remains unexplained. In this review, we will discuss the genetics of thrombocytopenia summarizing the recent advancement in investigation and diagnosis of IT using phenotypic approaches, high-throughput sequencing, targeted gene panels, and bioinformatics tools.

Myosin Heavy Chain 9: Oncogene or Tumor Suppressor Gene?

MYH9 was first discovered due to thrombocytopenia caused by MYH9 mutation-related abnormalities. In recent years, researchers have increasingly found that MYH9 plays an important role in cancer as a cytokine involved in cytoskeletal reorganization, cellular pseudopodia formation, and migration. MYH9 is closely related to the progress and poor prognosis of most solid tumors, and it is now accepted that MYH9 is a suppressor gene and plays an important role on the re-Rho pathway. Recent research has been limited to the study of tissues. However, it would be more direct and informative to be able to use hematology to assess tumor prognosis and changes in MYH9 levels and NMMHC-IIA. This article summarizes recent research on MYH9 and provides a reference for future clinical research.