Marked Underestimation of Platelet Count and a Characteristic Platelet Histogram as Clues to MYH9-Related Disorders.

BACKGROUND: The rapid development of automatic blood cell analyzers has greatly optimized complete blood count results. However, erroneous results relevant to automatic blood cell analyzers still exist. Pseudothrombocytopenia can be observed in both cases of anticoagulant-induced platelet aggregation, and the presence of large and giant platelets. METHODS: A rare case of a MYH9-related disorder, in which marked underestimation of platelet count was led by large and giant platelets using the impedance count by an automated hematology analyzer. Moreover, lancet-shaped and Dohle body-like cytoplasmic inclusions were detected in almost all white blood cells of the patient. RESULTS: The platelet count was done by an optical platelet counter or a fluorescence platelet counter, and peripheral blood smear was evaluated. In addition, the diagnosis of MYH9-related disorder was established by the molecular findings. CONCLUSIONS: Identification of the peripheral blood smear and familial history will eliminate the need for further laboratory testing and bone marrow examination.

A familial deletion of 10p12.1 associated with thrombocytopenia.

Thrombocytopenia can be inherited or acquired from a variety of causes. While hereditary causes of thrombocytopenia are rare, several genes have been associated with the condition. In this report, we describe an 18-year-old man and his mother, both of whom have congenital thrombocytopenia. Exome sequencing in the man revealed a 1006 kb maternally inherited deletion in the 10p12.1 region (arr[GRCh37] 10p12.1(27378928_28384564)x1) of uncertain clinical significance. This deletion in the THC2 locus includes genes ANKRD26, known to be involved in normal megakaryocyte differentiation, and MASTL, which some studies suggest is linked to autosomal dominant thrombocytopenia. In the family presented here, the deletion segregated with the congenital thrombocytopenia phenotype, suggesting that haploinsufficiency of one or both genes may be the cause. To our knowledge, this is the first report of a deletion of the THC2 locus associated with thrombocytopenia. Future functional studies of deletions of the THC2 locus may elucidate the mechanism for this phenotype observed clinically.

A nationwide survey of MYH9-related disease in Japan.

BACKGROUND: MYH9-related disease (MYH9-RD) is characterized by congenital macrothrombocytopenia, Döhle body-like granulocyte inclusions, and nephropathy, which may progress to end-stage kidney disease (ESKD). However, information on the effects of renin-angiotensin system (RAS) inhibitors on kidney survival is currently lacking and the outcomes of kidney replacement therapy (KRT) in MYH9-RD are largely unknown. METHODS: We conducted a cross-sectional nationwide survey by sending questionnaires to 145 institutions in Japan and analyzed data for 49 patients. RESULTS: The median patient age was 27 years. Genetic analysis was performed in 37 (76%) patients. Twenty-four patients (65%) had MYH9 variants affecting the motor domain of non-muscle myosin heavy chain-IIA, and these patients had poorer kidney survival than those with variants affecting the tail domain (P = 0.02). There was no significant difference in kidney survival between patients treated with and without RAS inhibitors. Hemodialysis and peritoneal dialysis were performed in 16 and 7 patients, respectively. There were no major bleeding complications during the perioperative period or during follow-up, except for one patient. Most of the 11 patients who underwent kidney transplantation required perioperative red cell concentrate transfusions, but there was no graft loss during the median posttransplant observational period of 2.0 (interquartile range, 1.3-6.8) years. CONCLUSION: Our study demonstrated no beneficial effect of RAS inhibitors on kidney function in patients with MYH9-RD, indicating the need for further studies with more patients. All modalities of KRT are feasible options for MYH9-RD patients who progress to ESKD, with adequate attention to bleeding complications.

Avatrombopag improves thrombocytopenia in MYH9-related disorder following eltrombopag treatment failure.

MYH9-related disorder (MYH9-RD) is autosomal dominant thrombocytopenia caused by mutations in the MYH9 gene, which codes for the non-muscle myosin-IIA heavy chain. We present a case of a 24-year-old Chinese man with MYH9-RD who was initially misdiagnosed with immune thrombocytopenia. Whole-exome sequencing and Sanger sequencing revealed a novel missense mutation in the MYH9 gene at the position of c.4550 G > T (p.G1517V) in exon 32. The same phenotype was observed in the proband, his mother, and his brother, in addition to macrothrombocytopenia and Dohle-like bodies in neutrophil granulocytes without non-hematologic manifestations. Following failed treatment with eltrombopag, avatrombopag, which was not mentioned before in the MYH9-RD treatment, was administered to the patient, and thrombocytopenia improved. In this case report, we present a novel pathogenic mutation and show the potential of avatrombopag for temporarily increasing the platelet count in patients with MYH9-RD.

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

Mutations in MYH9, the gene encoding the heavy chain of nonmuscle myosin IIa (NMII-A), cause MYH9-related disease (MYH9-RD), which 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 cyclic adenosine monophosphate (cAMP) signaling agonist. Then, we generated 2 knockin mouse lines, 1 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, whereas megakaryocyte-specific E1841K mice exhibited macrothrombocytopenia and a prolonged bleeding time with normal VWF release. Finally, we presented 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.

A gain-of-function variant in the Wiskott-Aldrich syndrome gene is associated with a MYH9-related disease-like syndrome.

While loss-of-function variants in the WAS gene are associated with Wiskott-Aldrich syndrome and lead to microthrombocytopenia, gain-of-function variants of WAS are associated with X-linked neutropenia (XLN) and the absence of microthrombocytopenia. Only a few XLN families have been reported so far, and their platelet phenotype was not described in detail. To date, no renal involvement was described in XLN. In the present study, we report exome sequencing of individuals from 3 generations of a family with a dominant disease combining neutropenia, macrothrombocytopenia, and renal failure. We identified a heterozygous missense gain-of-function variant in the WAS gene (c.881T>C, p.I294T) that segregates with the disease and is already known to cause XLN. There was no pathogenic variant in MYH9, TUBB1, or ACTN1. This is the first report of a WAS gain-of-function variant associated with both the hematological phenotype of XLN (neutropenia, macrothrombocytopenia) and renal disease (proteinuria, renal failure) with glomerular tip lesion hyalinosis and actin condensations in effaced podocytes foot processes.

Characterization of Sensorineural Hearing Loss in Patients With MYH9-Related Disease: A Systematic Review.

OBJECTIVES: To review the characteristics and progression of hearing loss in MYH9-related disease (MYH9-RD) patients and present a unique case of bilateral non-simultaneous sudden sensorineural hearing loss (SNHL) in an MYH9-RD patient. MYH9-RD is a rare autosomal dominant platelet disorder. Patients with this disorder have a variable risk of developing SNHL. METHODS: A comprehensive literature search for scientific articles in PubMed, Scopus, and Web of Science that reported hearing loss outcomes in MYH9-RD patients. RESULTS: Initial search yielded 270 studies. Eight studies with a total of 23 patients met inclusion criteria and were used for data analysis. MYH9-RD patients typically present with progressive bilateral SNHL affecting predominantly the high frequencies. Mean age of hearing loss onset was 17.1 years, progressing to severe-profound SNHL over a mean period of 14.4 years. Seventeen of the 23 patients received cochlear implant (CI) at a mean age of 37.9 years. In comparison, the study patient presented initially with bilateral progressive SNHL as a teenager and developed bilateral non-simultaneous sudden SNHL, first in her right ear at the age of 31 and 7 months later in her left ear at the age of 32. She is now a successful bilateral CI user. CONCLUSIONS: This is the first systematic investigation of the relationship between MYH9-RD patients and SNHL. Hearing loss in MYH9-RD patients is generally characterized as progressive SNHL. However, the study patient presented with the unique feature of bilateral non-simultaneous sudden SNHL, potentially expanding the hearing loss sequela associated with this disorder.

Successful cochlear implantation in a patient with Epstein syndrome during long-term follow-up.

Epstein syndrome is a rare disease characterized by macrothrombocytopenia, nephritis and progressive sensorineural hearing loss (SNHL). This syndrome is presently recognized as an autosomal dominant disease caused by mutations of non-muscle myosin heavy chain 9 (MYH9). Little information is available about the progress of SNHL, the efficacy of cochlear implants (CI) or the perioperative management of thrombocytopenia in patients with Epstein syndrome. We herein report a case of a patient with Epstein syndrome with the MYH9:c.2105G>A:p.R702H variant who underwent cochlear implantation after 27 years of follow-up for her progressive SNHL. The deterioration rates of hearing were 3.48 dB/year on the right ear and 2.46 dB/year on the left ear. The patient derived benefits from CI and had a speech recognition test result (for sentences) of 93% at 6-months postoperatively. Thrombocytopenia was successfully managed without any bleeding complications by using eltrombopag, an oral thrombopoietic agent, making transfusion of platelets unnecessary. The accurate diagnosis of Epstein syndrome was made only after long-term follow-up as the thrombocytopenia was initially diagnosed as idiopathic thrombocytopenic purpura. This case report highlights the perioperative management of thrombocytopenia, the progress of SNHL and the potential pitfalls of diagnosis.

[Gene analysis and clinical features of MYH9-related disease].

Objective: To identify gene variants and investigate clinical features of nonmuscle myosin heavy chain 9-related disease (MYH9-RD). Methods: In this retrospective study, the data of patients with MYH9-RD admitted to Shenzhen Children's Hospital from July 2017 to September 2020 were extracted. The gene variants, clinical features and laboratory tests results were summarized. Results: Among the 6 children, 4 were males and 2 were females, aged 4.0 (0.5-7.6) years. Main clinical manifestations included thrombocytopenia (6 cases), epistaxis (3 cases), petechias (2 cases), traumatic hematoma (1 case), and abnormal liver enzymes (1 case). One patient had no family history, and the other 5 cases were pedigrees. Two pedigrees (2 cases) had long-term microscopic hematuria, one pedigree (2 cases) had history of early cataract, and three pedigrees (5 cases) had chronic mild elevation of liver enzymes. Four MYH9 gene variants were found in 12 patients, including c.2104C>T(p.R702C) in exon 17, c.4270G>A(p.D1424N) in exon 31, c.5521G>A (p.E1841K) in exon 39, and c.5797C>T (p.R1933X) in exon 41. According to the family pedigrees analysis, except for the case of variant in exon 17 which was spontaneous mutation with no family history, the other variants were from their father or mother. The complete blood count results showed a decreased platelet number in these patients, and the counting results of the automated hematology analyzer were significantly lower than that of manual counting method ((33.4±17.2) × 109 vs. (60.4±21.0) × 109/L,t=-5.83, P<0.05). The examination of the peripheral blood smear revealed the presence of thrombocytopenia with giant platelets and granulocyte inclusion bodies. The MYH9 gene variant (R702C) located at the N-terminus head domain of non-muscle myosin heavy chain ⅡA (NMMHC-ⅡA), which has ATPase activity, led to severe reduction of platelet number (<20×109/L) and obscure granulocyte inclusion bodies. However, higher platelet numbers (40×109-80×109/L) and obvious granulocyte inclusion bodies were observed in patients with tail-position mutations at C-terminus. Conclusions: The clinical phenotypes of MYH9-RD were variable. The mutations in certain regions of MYH9 gene were related to platelet count and granulocyte inclusion bodies. MYH9-RD should be considered in individuals with unknown etiology and persistent thrombocytopenia which is non-responsive to conventional treatment, regardless of family history. Complete blood count and blood smear morphology examinations are the first steps to screen and diagnose the disease. The laboratory should pay attention to the morphological review rules and standardized reports.

[Clinical and genetic features of seven children with MYH9-related disease].

Objective: To summarize and analyze of the clinical and genetic characteristics of children with nonmuscle myosin heavy chain 9 (MYH9)-related disease (MYH9-RD). Methods: To screen the patients who were first diagnosed as "chronic/refractory immune thrombocytopenia (ITP) " from April 2016 to May 2019 in Beijing Children's Hospital by genetic and clinical examinations, then the clinical manifestation, laboratory examination and genetics results of 7 children diagnosed with MYH9-RD were collected and summarized retrospectively. Results: Among 7 children diagnosed with MYH9-RD, 3 were males and 4 females. The age of onset was 1.25 (0.41-6.16) years. The course of disease was 2.16 (0.41-8.59) years. The automatic platelet count was (9 (5-30))×109/L. All the cases were found with giant platelets under microscope,and the manual platelet count was (70 (30-100))×109/L. Four cases had skin hemorrhage or epistaxis and 3 cases had no bleeding. All 7 patients had received first-or second-line therapy of ITP, of whom 1 case received splenic embolization, and all the treatments mentioned above were ineffective. Finally, it was confirmed that all 7 patients had heterozygous missense mutations of MYH9 gene by next generation sequencing (NGS), including 2 pedigrees and 5 sporadic cases. Four sporadic mutations occurred in N-terminal globular head domain (HD), and 1 sporadic case with p.D1424N mutations occurred in the C-terminal tail domain (TD). One of the pedigrees also had p.D1424N mutation. The other familial case had a novel variant with one missense variant p.A44D caused by the c.131C>A transition. One of the two p.R702 mutations had kidney damage, and several relatives of the new p.A44D mutations had deafness. Conclusions: In this study, the spontaneous mutations of seven MYH9-RD were common, and all patients were misdiagnosed as ITP, whereas the bleeding was mild and immunotherapy was ineffective. The suspected disease can be identified earlier by manual visual platelet volume and count, which can be confirmed by genetic testing. It is more important to monitor the development of other organs damage instead of thrombocytopenia. For cases with p.R702 mutations the doctor should be aware of kidney damage, and for the cases with novel mutations p.A44D the doctor should be aware of hearing loss.

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.

Familial thrombocytopenia due to a complex structural variant resulting in a WAC-ANKRD26 fusion transcript.

Advances in genome sequencing have resulted in the identification of the causes for numerous rare diseases. However, many cases remain unsolved with standard molecular analyses. We describe a family presenting with a phenotype resembling inherited thrombocytopenia 2 (THC2). THC2 is generally caused by single nucleotide variants that prevent silencing of ANKRD26 expression during hematopoietic differentiation. Short-read whole-exome and genome sequencing approaches were unable to identify a causal variant in this family. Using long-read whole-genome sequencing, a large complex structural variant involving a paired-duplication inversion was identified. Through functional studies, we show that this structural variant results in a pathogenic gain-of-function WAC-ANKRD26 fusion transcript. Our findings illustrate how complex structural variants that may be missed by conventional genome sequencing approaches can cause human disease.

Role of Thrombopoietin Receptor Agonists in Inherited Thrombocytopenia.

In the last decade, improvements in genetic testing have revolutionized the molecular diagnosis of inherited thrombocytopenias (ITs), increasing the spectrum of knowledge of these rare, complex and heterogeneous disorders. In contrast, the therapeutic management of ITs has not evolved in the same way. Platelet transfusions have been the gold standard treatment for a long time. Thrombopoietin receptor agonists (TPO-RA) were approved for immune thrombocytopenia (ITP) ten years ago and there is evidence for the use of TPO-RA not only in other forms of ITP, but also in ITs. We have reviewed in the literature the existing evidence on the role of TPO-RAs in ITs from 2010 to February 2021. A total of 24 articles have been included, 4 clinical trials, 3 case series and 17 case reports. A total of 126 patients with ITs have received TPO-RA. The main diagnoses were Wiskott-Aldrich syndrome, MYH9-related disorder and ANKRD26-related thrombocytopenia. Most patients were enrolled in clinical trials and were treated for short periods of time with TPO-RA as bridging therapies towards surgical interventions, or other specific approaches, such as hematopoietic stem cell transplantation. Here, we have carried out an updated and comprehensive review about the efficacy and safety of TPO-RA in ITs.

The May-Hegglin anomaly: a rare cause of a common complaint.

May-Hegglin anomaly is the presentation of a qualitative platelet disorder characterised by large platelets, thrombocytopenia and granulocyte inclusions as a result of mutations in the MYH9 gene. Though often overlooked given its rarity, it should be considered in patients who present with epistaxis, bruising, menorrhagia and easy bleeding as it can be mistaken for other diagnoses resulting in unnecessary treatments and tests. Our case study reports one presentation of this anomaly and can help broaden awareness of the presentation of this type of patient.

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.