MYH9-related disease with a normal platelet count

MYH9-related disease (MYH9-RD) is characterized by congenital macrothrombocytopenia, progressive kidney failure, and sensorineural hearing loss. We describe a patient with MYH9-RD and a normal platelet count. A 13-year-old boy with a normal platelet count presented with proteinuria and hematuria and underwent a kidney biopsy. Light microscopy showed mild mesangial matrix expansion. Electron microscopy showed thinning of the glomerular basement membrane and splitting of the lamina densa. A tentative diagnosis of Alport syndrome was made. Unexpectedly, genetic analysis revealed a de novo MYH9 gene variant (p.Gln1068_Leu1074dup). A peripheral blood smear examination showed giant platelets and leukocyte inclusion bodies, confirming a diagnosis of MYH9-RD. In summary, we described a patient with MYH9-RD without thrombocytopenia who showed glomerular basement membrane abnormalities similar to Alport syndrome. Peripheral blood smear examinations may be helpful for an appropriate diagnosis of MYH9-RD, even in patients with proteinuria and a normal platelet count.

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.

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.

Heterozygous MYH9 Mutations in 2 Children With Cochlear Nerve Canal Stenosis

MYH9 is a gene that encodes for a subunit of the myosin heavy chain IIA protein. Mutations in MYH9 are associated with hematologic abnormalities, renal dysfunction, and hearing loss. Bony cochlear nerve canal stenosis (CNCS), which is diagnosed on computed tomography (CT) imaging, has been associated with congenital deafness, cochlear nerve aplasia/hypoplasia, and inner ear malformations. We report two cases of CNCS presenting with profound congenital hearing loss whom we diagnosed with mutations in MYH9 and discuss the genotype-phenotype association and implications for management.

Treatment of inherited thrombocytopenias

The new techniques of genetic analysis have made it possible to identify many new forms of inherited thrombocytopenias (IT) and study large series of patients. In recent years, this has changed the view of IT, highlighting the fact that, in contrast to previous belief, most patients have a modest bleeding diathesis. On the other hand, it has become evident that some of the mutations responsible for platelet deficiency predispose the patient to serious, potentially life-threatening diseases. Today's vision of IT is, therefore, very different from that of the past and the therapeutic approach must take these changes into account while also making use of the new therapies that have become available in the meantime. This review, the first devoted entirely to IT therapy, discusses how to prevent bleeding in those patients who are exposed to this risk, how to treat it if it occurs, and how to manage the serious illnesses to which patients with IT may be predisposed.

The surgical management of a patient with chronic renal failure and macrothrombocytopenia related to the MYH9 gene mutation: A case report

MYH9 disease is a rare genetic disorder in which there is a mutation in the gene for the non-muscle myosin heavy chain IIA. It initially causes macrothrombocytopenia followed by other clinical manifestations. When the patient reaches adulthood, he can develop chronic kidney failure. Thus, the risk of suffering a hemorrhage, difficulty in repairing and, infections increases in individuals with this disease. In addition, the use of drugs in these patients should be carefully evaluated. An adult patient sought dental care with a complaint associated with a tooth with advanced dental caries. He had severe thrombocytopenia (7000 platelets/mm³ ), hearing loss, and chronic kidney failure. The diagnosis of MYH9 disease was confirmed through genotyping. After clinical examination, extraction was planned. Local and systemic procedures were used to prevent hemorrhage, especially postoperatively. Although the patient had an infection at the surgical wound site and no episode of postoperative bleeding, the repair process occurred normally. The purpose of this article is to report the surgical management of a patient with MYH9 disease.

Myosin Heavy Chain 9 (MYH9)-Related Congenital Macrothrombocytopenia

Myosin heavy chain 9 (MYH9)-related hereditary macrothrombocytopenia is caused by mutation of the MYH9 gene encoding the heavy chain A of non-muscle myosin of class II. We present a case that emphasizes the importance of awareness of rare disorders which could potentially avoid over-investigation, especially in benign conditions.

A 72-year-old Caucasian female presented for preoperative evaluation for cataract extraction. She was noted to have thrombocytopenia of 30 K/uL along with elevated creatinine. She denied any acute symptoms except for a prolonged history of easy bruising. Physical exam revealed bruising over the extremities. Upon further questioning, she was previously investigated for thrombocytopenia and had multiple diagnostic as well as therapeutic interventions including bone marrow biopsies, steroids, intravenous immunoglobulins with no improvement. Her family history is consistent with low platelet counts for at least three generations. Peripheral blood smear showed large platelets, normal red and white blood cells with Döhle bodies. Further genetic testing revealed an inherited MYH9 mutation which is autosomal dominant.

MYH9-related disorders are characterized by macrothrombocytopenia, often associated with glomerulonephritis, sensorineural deafness, cataracts, and cytoplasmic inclusion bodies within leukocytes. Management is mainly conservative and directed towards the prevention of iron deficiency anemia in young females. The use of desmopressin, in combination with tranexamic acid, is recommended in a perioperative setting. Our case emphasizes the importance of history-taking skills that could potentially minimize further diagnostic or therapeutic interventions in this benign genetic disorder.

Diagnosing Inherited Platelet Disorders: Modalities and Consequences

Inherited platelet disorders (IPDs) are a group of rare conditions featured by reduced circulating platelets and/or impaired platelet function causing variable bleeding tendency. Additional hematological or non hematological features, which can be congenital or acquired, distinctively mark the clinical picture of a subgroup of patients. Recognizing an IPD is challenging, and diagnostic delay or mistakes are frequent. Despite the increasing availability of next-generation sequencing, a careful phenotyping of suspected patients-concerning the general clinical features, platelet morphology, and function-is still demanded. The cornerstones of IPD diagnosis are clinical evaluation, laboratory characterization, and genetic testing. Achieving a diagnosis of IPD is desirable for several reasons, including the possibility of tailored therapeutic strategies and individual follow-up programs. However, detailed investigations can also open complex scenarios raising ethical issues in case of IPDs predisposing to hematological malignancies. This review offers an overview of IPD diagnostic workup, from the interview with the proband to the molecular confirmation of the suspected disorder. The main implications of an IPD diagnosis are also discussed.

Case Report: Pathogenic MYH9 c.5797delC Mutation in a Patient With Apparent Thrombocytopenia and Nephropathy

MYH9-related disease or disorder (MYH9-RD) is an autosomal dominant disease caused by mutations in the MYH9 gene. Mutations in this gene initially affect the hemic system, and other manifestations may evolve with age. Here, we report the case of a 46-year-old Chinese woman with MYH9-RD who was primarily misdiagnosed with idiopathic thrombocytopenia purpura. Exome sequencing of the patient, and the mother and son of the patient revealed a deletion mutation c.5797delC (p. R1933Efs^*15) in exon 41 (encoding non-helical tailpiece, NHT) of the MYH9 gene, which consequently led to a frameshift mutation. To the best of our knowledge, this mutation has been reported in Italy once, while the substitution mutation c.5797 C>T is the most frequent mutation. Mutations that affect the NHT region cause thrombocytopenia throughout life; however, our patient presented with a more severe phenotype than previously reported, including thrombocytopenia, inclusion bodies in neutrophils, sensorineural hearing loss, nephropathy, and abnormal liver enzymes. Our goal in the current case is to prevent further progression of renal involvement and to identify other affected members in this family to provide early intervention. This case may raise awareness of MYH9-RD when diagnosing thrombocytopenia and improve our understanding of this condition.

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.

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.

Relation between mutations in the 5' UTR of ANKRD26 gene and inherited thrombocytopenia with predisposition to myeloid malignancies. An Egyptian study

Inherited thrombocytopenias are a heterogeneous group of diseases characterized by a reduced number of platelets and a bleeding tendency that ranges from very mild to life threatening especially in surgery. Mutations in the 5' untranslated region (UTR) of Ankirin repeat domain 26 (ANKRD26) are responsible for autosomal-dominant form of thrombocytopenia, that is known as ANKRD26-related thrombocytopenia (ANKRD26 RT), characterized by a moderate thrombocytopenia with mild propensity to bleeding and predisposition to hematological malignancies including AML and MDS. We included 90 unrelated patients with inherited thrombocytopenia. In addition, we investigated 45 patients with ITP. Peripheral blood and bone marrow samples were collected and examined and molecular detection of mutations in the 5︡ UTR of ANKRD26 gene was performed for all the patients. Also, screening of the mutation and development of myeloid malignancies in the extended series of the affected subjects was done. ANKRD26 mutations were identified in 10% of the patients with inherited thrombocytopenia. The most common types were c.128 G > A and c.127A>T, while no mutations were found in the ITP group. In those affected, the median number of platelets was 69 x10⁹/L (43-106) with normal MPV in most of the patients (9.4-11.6). There was a statistically significant increase in the unexpected high frequency of myeloid malignancies in the extended series of the mutated subjects compared with the ITP group-extended series (P < .001). So, we can conclude that ANKRD26 RT is associated with increased risk for developing myeloid malignancies and ANKRD26 mutations can represent a valuable tool for making therapeutic decisions.

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.

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.

Two Cases of the MYH9 Disorder Fechtner Syndrome Diagnosed from Observation of Peripheral Blood Cells before End-Stage Renal Failure

As a MYH9 disorder, Fechtner syndrome is characterized by nephritis, giant platelets, granulocyte inclusion bodies (Döhle-like bodies), cataract, and sensorineural deafness. Observation of peripheral blood smear for the presence of thrombocytopenia, giant platelets, and granulocyte inclusion bodies (Döhle-like bodies) is highly important for the early diagnosis of MYH9 disorders. In our two cases, sequencing analysis of the MYH9 gene indicated mutations in exon 24. Both cases were diagnosed as the MYH9 disorders Fechtner syndrome before end-stage renal failure on the basis of the observation of peripheral blood smear.

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.

Simplifying the diagnosis of inherited platelet disorders? The new tools do not make it any easier

The molecular causes of many inherited platelet disorders are being unraveled. Next-generation sequencing facilitates diagnosis in 30% to 50% of patients. However, interpretation of genetic variants is challenging and requires careful evaluation in the context of a patient's phenotype. Before detailed testing is initiated, the treating physician and patient should establish an understanding of why testing is being performed and discuss potential consequences, especially before testing for variants in genes associated with an increased risk for hematologic malignancies.

Diagnosis of hereditary platelet disorders in the era of next-generation sequencing: "primum non nocere"

Inherited platelet disorders can affect "only platelets", occur as a "syndromic phenotype" or be associated with "increased risk of hematological malignancies". Genetic testing is attractive for diagnosis of inherited platelet disorders. However, many physicians who refer patient blood for genetic testing are unaware of the association of certain inherited platelet disorders with other risks. Inherited platelet disorders associated with minor-moderate bleeding rarely cause patient distress. In contrast, identification of a mutation associated with an increased risk of leukemia may cause a major psychological disease burden, without offsetting the beneficial impact on management. Guidelines recommend postponing genetic testing "until the patient reaches adulthood or at least until the child is mature enough to participate in decision making". In our opinion, outside research, (genetic) testing in children with inherited platelet disorders should only be performed if it influences management. In adults, genes causing inherited platelet disorders associated with an increased risk of hematological malignancies should only be tested after obtaining explicit informed consent.

MYH9: Structure, functions and role of non-muscle myosin IIA in human disease

The MYH9 gene encodes the heavy chain of non-muscle myosin IIA, a widely expressed cytoplasmic myosin that participates in a variety of processes requiring the generation of intracellular chemomechanical force and translocation of the actin cytoskeleton. Non-muscle myosin IIA functions are regulated by phosphorylation of its 20 kDa light chain, of the heavy chain, and by interactions with other proteins. Variants of MYH9 cause an autosomal-dominant disorder, termed MYH9-related disease, and may be involved in other conditions, such as chronic kidney disease, non-syndromic deafness, and cancer. This review discusses the structure of the MYH9 gene and its protein, as well as the regulation and physiologic functions of non-muscle myosin IIA with particular reference to embryonic development. Moreover, the review focuses on current knowledge about the role of MYH9 variants in human disease.

Macrothrombocytopenia, renal dysfunction and nephrotic syndrome in a young male patient: a case report of MYH9-related disease

MYH9-related disease is an autosomal dominant disorder caused by mutations of the MYH9 gene, which encodes the non-muscle myosin heavy chain IIA on chromosome 22q12. It is characterized by congenital macrothrombocytopenia, bleeding tendency, hearing loss, and cataracts. Nephropathy occurs in approximately 30% of MYH9-related disease in a male patient carrier of a de novo missense mutation in exon 1 of the MYH9 gene [c.287C > T; p.Ser(TCG)96(TTG)Leu]. He presented all phenotypic manifestations of the disease, but cataracts. Renal alterations were microhematuria, nephrotic-range proteinuria (up to 7.5 g/24h), and rapid loss of renal function. The decline per year of the glomerular filtration rate was 20 mL/min/1.73m² for five years. Blockade of the renin-angiotensin system, the only recommended therapy for slowing the progression of this nephropathy, was prescribed. Although MYH9-related disease is a rare cause of glomerulopathy and end-stage renal disease, awareness of rare genetic kidney disorders is essential to ensure accurate diagnosis and proper management of orphan disease patients.

Clinic, pathogenic mechanisms and drug testing of two inherited thrombocytopenias, ANKRD26-related Thrombocytopenia and MYH9-related diseases

Inherited thrombocytopenias (ITs) are a heterogeneous group of disorders characterized by low platelet count resulting in impaired hemostasis. Patients can have spontaneous hemorrhages and/or excessive bleedings provoked by hemostatic challenges as trauma or surgery. To date, ITs encompass 32 different rare monogenic disorders caused by mutations of 30 genes. This review will focus on the major discoveries that have been made in the last years on the diagnosis, treatment and molecular mechanisms of ANKRD26-Related Thrombocytopenia and MYH9-Related Diseases. Furthermore, we will discuss the use a Thrombopoietin mimetic as a novel approach to treat the thrombocytopenia in these patients. We will propose the use of a new 3D bone marrow model to study the mechanisms of action of these drugs and to test their efficacy and safety in patients. The overall purpose of this review is to point out that important progresses have been made in understanding the pathogenesis of ANKRD26-Related Thrombocytopenia and MYH9-Related Diseases and new therapeutic approaches have been proposed and tested. Future advancement in this research will rely in the development of more physiological models to study the regulation of human platelet biogenesis, disease mechanisms and specific pharmacologic targets.

Macrothrombocytopenia With Congenital Bilateral Cataracts: A Phenotype of MYH9 Disorder With Exon 24 Indel Mutations

MYH9 disorder is characterized by large platelets and granulocyte inclusion bodies, and can be complicated with young-adult onsets of nephropathy, sensorineural hearing loss, and cataracts. Congenital cataracts in patients with MYH9 disorder is rare, and their etiology has not been elucidated. We report a 3-year-old patient with MYH9 disorder who had a p.E1066_A1072del mutation and developed cataracts congenitally. A review of the literature reveals that patients with an MYH9 exon 24 indel mutation, including p.E1066_A1072del, are susceptible to developing congenital cataracts and should be followed closely for other nonhematological complications.

Hereditary thrombocytopenias: a growing list of disorders

The introduction of high throughput sequencing (HTS) techniques greatly improved the knowledge of inherited thrombocytopenias (ITs) over the last few years. A total of 33 different forms caused by molecular defects affecting at least 32 genes have been identified; along with the discovery of new disease-causing genes, pathogenetic mechanisms of thrombocytopenia have been better elucidated. Although the clinical picture of ITs is heterogeneous, bleeding has been long considered the major clinical problem for patients with IT. Conversely, the current scenario indicates that patients with some of the most common ITs are at risk of developing additional disorders more dangerous than thrombocytopenia itself during life. In particular, MYH9 mutations result in congenital macrothrombocytopenia and predispose to kidney failure, hearing loss, and cataracts, MPL and MECOM mutations cause congenital thrombocytopenia evolving into bone marrow failure, whereas thrombocytopenias caused by RUNX1, ANKRD26, and ETV6 mutations are characterized by predisposition to hematological malignancies. Making a definite diagnosis of these forms is crucial to provide patients with the most appropriate treatment, follow-up, and counseling. In this review, the ITs known to date are discussed, with specific attention focused on clinical presentations and diagnostic criteria for ITs predisposing to additional illnesses. The currently available therapeutic options for the different forms of IT are illustrated.

Macrothrombocytopenia With Döhle Body-Like Granulocyte Inclusions: A Case Report of May-Hegglin Anomaly in a 33-Year-Old White Woman With an Update on the Molecular Findings of MYH9-Related Disease

A 33-year-old white woman arrived at the hospital to undergo a hysterectomy due to uterine fibroids. Blood smear review identified macrothrombocytopenia and Döhle body-like cytoplasmic leukocyte inclusions. Genetic testing identified a mutation in exon 39 of the myosin heavy chain gene (MHY9; OMIM 160775), which confirmed the diagnosis of May-Hegglin anomaly. May-Hegglin anomaly is one of a spectrum of MYH9 disorders that also includes Sebastian, Epstein, and Fechtner syndromes. Herein, we describe the clinical and laboratory presentation of a patient with May-Hegglin anomaly and provide an update on the molecular findings and a discussion of the genotypic-phenotypic correlations in this potentially underdiagnosed disorder.

Sporadic Epstein syndrome with macrothrombocytopenia, sensorineural hearing loss and renal failure

We report here a sporadic case of Epstein syndrome, one of the MYH9 disorders. A Japanese boy was first noted to have thrombocytopenia at 3 years of age. Blood smear showed giant platelets but no Döhle-like bodies in the neutrophils. He had no family history of thrombocytopenia, hearing loss, and/or renal failure. Thrombocytopenia took a chronic course and platelet count fluctuated in the range 18 000-46 000/μL, not responding to i.v. immunoglobulin or prednisolone treatment. The patient had episodes of gross nasal bleeding at 7 and 18 years of age. Mild hearing loss was suspected at 6, and proteinuria was first noted at 14 years of age. At the development of renal failure at 24 years of age, he was identified to have de novo R702H MYH9 mutation. This case illustrates the importance of suspecting MYH9 disorder even in cases of chronic macrothrombocytopenia without family history.

Diagnosis and treatment of inherited thrombocytopenias

Knowledge in the field of inherited thrombocytopenias (ITs) has greatly improved over the last 15 years. Several new genes responsible for thrombocytopenia have been identified leading to the definition of novel nosographic entities and to a much better characterization of the phenotypes of these diseases. To date, ITs encompass 22 disorders caused by mutations in 24 genes and characterized by different degrees of complexity and great variability in prognosis. Making a definite diagnosis is important for setting an appropriate follow-up, choosing the best treatments and providing proper counseling. Despite the abovementioned progress, diagnosis of ITs remains difficult and these disorders are still underdiagnosed. The purpose of this review is to provide an updated guide to the diagnosis of ITs based on simple procedures. Moreover, the currently available therapeutic options for these conditions are recapitulated and discussed.

MYH9 nephropathy

MYH9-related disorder is an autosomal dominant disease caused by a mutation in the MYH9 gene, which encodes nonmuscle myosin heavy chain IIA (NMMHC-IIA). This disease is characterized by giant platelets, thrombocytopenia, granulocyte inclusion bodies, proteinuria, and high-pitch sensorineural deafness. Nephropathy has been observed in 30% of patients with MYH9-related disorder. The characteristic features are early onset proteinuria and rapidly progressing renal disorder. However, the prognosis of MYH9 nephropathy remains unclear. Herein, we describe a 36-year-old woman who presented with proteinuria and was diagnosed with MYH9 nephropathy via renal biopsy and gene analysis. Her proteinuria improved after administration of an angiotensin II receptor blocker, but was aggravated after changing to a calcium channel blocker.

Congenital thrombocytopenia: clinical manifestations, laboratory abnormalities, and molecular defects of a heterogeneous group of conditions

Once considered exceptionally rare, congenital thrombocytopenias are increasingly recognized as a heterogeneous group of disorders characterized by a reduction in platelet number and a bleeding tendency that may range from very mild to life threatening. Although some of these disorders affect only megakaryocytes and platelets, others involve different cell types and may result in characteristic phenotypic abnormalities. This review elaborates the clinical presentation and laboratory manifestations of common congenital thrombocytopenias in addition to exploring our understanding of the molecular basis of these disorders and therapeutic interventions available.

MYH9-related disease: a novel prognostic model to predict the clinical evolution of the disease based on genotype-phenotype correlations

MYH9-related disease (MYH9-RD) is a rare autosomal-dominant disorder caused by mutations in the gene for nonmuscle myosin heavy chain IIA (NMMHC-IIA). MYH9-RD is characterized by a considerable variability in clinical evolution: patients present at birth with only thrombocytopenia, but some of them subsequently develop sensorineural deafness, cataract, and/or nephropathy often leading to end-stage renal disease (ESRD). We searched for genotype-phenotype correlations in the largest series of consecutive MYH9-RD patients collected so far (255 cases from 121 families). Association of genotypes with noncongenital features was assessed by a generalized linear regression model. The analysis defined disease evolution associated to seven different MYH9 genotypes that are responsible for 85% of MYH9-RD cases. Mutations hitting residue R702 demonstrated a complete penetrance for early-onset ESRD and deafness. The p.D1424H substitution associated with high risk of developing all the noncongenital manifestations of disease. Mutations hitting a distinct hydrophobic seam in the NMMHC-IIA head domain or substitutions at R1165 associated with high risk of deafness but low risk of nephropathy or cataract. Patients with p.E1841K, p.D1424N, and C-terminal deletions had low risk of noncongenital defects. These findings are essential to patients' clinical management and genetic counseling and are discussed in view of molecular pathogenesis of MYH9-RD.

Myosin heavy chain-9-related disorders (MYH9-RD): a case report

Myosin heavy chain-9-related disorders (MYH9-RDs) are a group of autosomal-dominant disorders caused by mutations in the MYH9 gene. The features include congenital macrothrombocytopaenia, inclusion bodies in neutrophils and a variable risk of developing sensorineural deafness, progressive renal impairment and presenile cataracts. A 44-year-old Caucasian man was initially thought to have Alport's syndrome and thrombocytopaenia secondary to idiopathic thrombocytopaenic purpura (ITP). A detailed family history and genetic analysis revealed a diagnosis of MYH9-RD. This case highlights the implications of a delayed diagnosis and the ongoing challenges encountered during management of individuals with this condition.

Familial cases with MYH9 disorders caused by MYH9 S96L mutation

We report familial cases with MYH9 disorders: a 1-year-old Japanese boy who presented only with macrothrombocytopenia, and his 33-year-old father who had been diagnosed with refractory chronic idiopathic thrombocytopenic purpura, and suffered from hearing loss and chronic renal failure. Peripheral blood smears revealed giant platelets but no Döhle body-like cytoplasmic inclusion bodies in neutrophils. Heterozygous MYH9 S96L mutations were found in the patient and his father, resulting in the diagnosis of a familial case with MYH9 disorders. The possibility of MYH9 disorders including Epstein syndrome should be assessed in cases of thrombocytopenia through the careful examination of hematological features.

Clinical, pathological, and genetic analysis of ten patients with MYH9-related disease

MYH9-related disease (MYH9-RD) is an autosomal dominant disorder caused by mutations in the MYH9 gene. It is characterized by a triad of giant platelets, thrombocytopenia, and characteristic Döhle body-like granulocyte inclusions. In this study we report 10 unrelated patients with MYH9-RD in whom the following seven MYH9 gene mutations were found: W33R, p.Q1443_K1445dup, R702H, D1424N, E1841K, R1933X, and E1945X (the first two were novel mutations). The region of the MYH9 mutation determines in some regards the phenotype, but clinical expression can vary between individuals with the same mutation. The neutrophil inclusion bodies of two patients were too small to be detected, but could be found with immunofluorescence staining. Immunoblotting analysis revealed that the calculated NMMHC-IIA/β-actin ratio for MYH9-RD neutrophils was 39% of normal controls. Kidney biopsy showed segmental glomerulosclerosis and NMMHC-IIA expression was decreased in podocytes. This disease is not as rare as originally thought. In any individual with persistent macrothrombocytopenia and no response to corticosteroids and immunosuppressive agents, even if neutrophil inclusions were inconspicuous in routine staining, MYH9-RD should be suspected.

MYH9-related disease: five novel mutations expanding the spectrum of causative mutations and confirming genotype/phenotype correlations

MYH9-related disease (MYH9-RD) is a rare autosomal dominant syndromic disorder caused by mutations in MYH9, the gene encoding for the heavy chain of non-muscle myosin IIA (myosin-9). MYH9-RD is characterized by congenital macrothrombocytopenia and typical inclusion bodies in neutrophils associated with a variable risk of developing sensorineural deafness, presenile cataract, and/or progressive nephropathy. The spectrum of mutations responsible for MYH9-RD is limited. We report five families, each with a novel MYH9 mutation. Two mutations, p.Val34Gly and p.Arg702Ser, affect the motor domain of myosin-9, whereas the other three, p.Met847_Glu853dup, p.Lys1048_Glu1054del, and p.Asp1447Tyr, hit the coiled-coil tail domain of the protein. The motor domain mutations were associated with more severe clinical phenotypes than those in the tail domain.

Inherited thrombocytopenias: the evolving spectrum

The chapter of inherited thrombocytopenias has expanded greatly over the last decade and many "new" forms deriving from mutations in "new" genes have been identified. Nevertheless, nearly half of patients remain without a definite diagnosis because their illnesses have not yet been described. The diagnostic approach to these diseases can still take advantage of the algorithm proposed by the Italian Platelet Study Group in 2003, although an update is required to include the recently described disorders. So far, transfusions of platelet concentrates have represented the main tool for preventing or treating bleedings, while haematopoietic stem cell transplantation has been reserved for patients with very severe forms. However, recent disclosure that an oral thrombopoietin mimetic is effective in increasing platelet count in patients with MYH9-related thrombocytopenia opened new therapeutic perspectives. This review summarizes the general aspects of inherited thrombocytopenias and describes in more detail MYH9-related diseases (encompassing four thrombocytopenias previously recognized as separate diseases) and the recently described ANKRD26-related thrombocytopenia, which are among the most frequent forms of inherited thrombocytopenia.

MYH9-related disorders: report on a patient of Greek origin presenting with macroscopic hematuria and presenile cataract, caused by an R1165C mutation

Myosin heavy chain-9 (MYH9)-related disorders represent a heterogenous group of hereditary diseases caused by mutations in the gene encoding the heavy chain of nonmuscle myosin IIA. May-Hegglin anomaly and Fechtner, Sebastian, and Epstein syndromes are the four phenotypes of the disease, characterized by congenital macrothrombocytopenia and distinguished by different combinations of clinical signs that may include glomerulonephritis, sensorineural hearing loss, and presenile cataract. The spectrum of mutations responsible for the disease is wide and the existence of genotype-phenotype correlation remains a critical issue. We report the first case of an MYH9-RD in a patient of Greek origin presenting with macroscopic hematuria and presenile cataract caused by a p.R1165C mutation. The same mutation was present in the patient's father, who exhibited no extrahematological features of the disease. The p.R1165C mutation is one of the MYH9 alterations whose prognostic significance is still poorly defined. Thus, the patients described add to the limited existing data on the MYH9 mutations and their resultant phenotypes.

Alteration of liver enzymes is a feature of the MYH9-related disease syndrome

Background

MYH9-related disease (MYH9-RD) is a rare autosomal dominant genetic syndrome characterized by congenital thrombocytopenia associated with the risk of developing progressive nephropathy, sensorineural deafness, and presenile cataract. During the collection of a large case-series of patients with MYH9-RD we noticed several cases with unexplained elevation of liver enzymes. Our aim was to evaluate if the alteration of liver tests is a feature of the MYH9-RD and to define its clinical significance.

Methods and Findings

Data concerning liver tests, prospectively recorded in the Italian Registry for MYH9-RD, were collected and compared with those of three control populations: patients with autoimmune thrombocytopenia, patients with inherited thrombocytopenias other than MYH9-RD, and the participants to a large epidemiologic survey in an Italian geographic isolate. Thirty-eight of 75 evaluable MYH9-RD patients (50.7%) showed an elevation of ALT and/or AST, and 17 of 63 (27.0%) an increase of GGT. The increases ranged from 1.9±0.7 to 2.7±1.6 fold the upper normal limit. The prevalence of liver test alterations was significantly higher in MYH9-RD patients than in each of the control populations, with odds ratios ranging from 8.2 (95% CIs 2.2–44.8) to 24.7 (14.8–40.8). Clinical follow-up and more detailed liver studies of a subset of patients, including ultrasound liver scan, liver elastography and liver biopsy in one case, did not show any significant structural damage or evolution towards liver insufficiency.

Conclusions

Elevation of liver enzymes is a frequent and previously unrecognized feature of the MYH9-RD syndrome; however, this defect does not appear to have poor prognostic value.

Mutations in ANKRD26 are responsible for a frequent form of inherited thrombocytopenia: analysis of 78 patients from 21 families

Until recently, thrombocytopenia 2 (THC2) was considered an exceedingly rare form of autosomal dominant thrombocytopenia and only 2 families were known. However, we recently identified mutations in the 5'-untranslated region of the ANKRD26 gene in 9 THC2 families. Here we report on 12 additional pedigrees with ANKRD26 mutations, 6 of which are new. Because THC2 affected 21 of the 210 families in our database, it has to be considered one of the less rare forms of inherited thrombocytopenia. Analysis of all 21 families with ANKRD26 mutations identified to date revealed that thrombocytopenia and bleeding tendency were usually mild. Nearly all patients had no platelet macrocytosis, and this characteristic distinguishes THC2 from most other forms of inherited thrombocytopenia. In the majority of cases, platelets were deficient in glycoprotein Ia and α-granules, whereas in vitro platelet aggregation was normal. Bone marrow examination and serum thrombopoietin levels suggested that thrombocytopenia was derived from dysmegakaryopoiesis. Unexplained high values of hemoglobin and leukocytes were observed in a few cases. An unexpected finding that warrants further investigation was a high incidence of acute leukemia. Given the scarcity of distinctive characteristics, the ANKRD26-related thrombocytopenia has to be taken into consideration in the differential diagnosis of isolated thrombocytopenias.

MYH-9 Related Platelet Disorders: Strategies for Management and Diagnosis

MYH-9 related platelet disorders belong to the group of inherited giant platelet disorders. The MYH-9 gene encodes the non-muscular myosin heavy chain IIA (NMMHCIIA), a cytoskeletal contractile protein. Several mutations in the MYH-9 gene lead to macrothrombocytopenia, and cytoplasmic inclusion bodies within leukocytes, while the number of megakaryocytes in the bone marrow is normal. Four overlapping syndromes, known as May-Hegglin anomaly, Epstein syndrome, Fechtner syndrome and Sebastian platelet syndrome, describe different clinical manifestations of MYH9 gene mutations. Macrothrombocytopenia is present in all affected individuals, whereas only some develop additional clinical manifestations such as renal failure, hearing loss and presenile cataracts. The bleeding tendency is usually moderate, with menorrhagia and easy bruising being most frequent. The biggest risk for the individual is inappropriate treatment due to misdiagnosis of chronic autoimmune thrombocytopenia. More than 30 mutations within the 40 exons of the MYH-9 gene leading to macrothrombocytopenia have been identified, of which the upstream mutations up to amino acid ~1400 are more likely associated with syndromic manifestations than the downstream mutations. Diagnosis is based on identification of the granulocyte inclusion bodies using blood smears and immunofluorescence and is finally confirmed by identifying the mutation. Treatment is supportive and should be aimed to prevent iron deficiency anemia. Beside renal failure, the biggest risk for patients affected by a MYH-9 disorder are the adverse effects resulting form treatment based on the misdiagnosis of immune thrombocytopenia.