Historical hematology: May-Hegglin anomaly

MYH9 disorder: Identification and a novel mutation in patients with macrothrombocytopenia

The diagnosis of MYH9 disorder is guided by recognizing granulocyte Döhle body-like inclusion bodies and large/giant platelets in the peripheral blood smear. Immunofluorescence study of nonmuscle myosin heavy chain IIA is a sensitive screening method for diagnosis of MYH9 disorder. The diagnosis can then be confirmed by genetic analysis. A total of 67 patients with macrothrombocytopenia were included, of which 11 patients (16%), aged 4 months to 22 years, were ultimately diagnosed with MYH9 disorder. One novel mutation in exon 30 at c.4338T>C (p.F1446A) was detected. This mutation was associated with nonhematologic manifestations presenting in late adolescence with cataracts, hearing loss, and hematuria.

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.

Identification of a Novel MYH9 Mutation in a Young Adult With Inherited Thrombocytopenia and Recurrent Seizures by Targeted Exome Sequencing

May-Hegglin anomaly (MHA) is a rare autosomal dominant disorder caused by a mutation in the myosin heavy chain 9 (MYH9) gene. MHA patients have variable clinical manifestations including thrombocytopenia, renal injury, hearing impairment, and cataracts. We describe a 25-year-old man with isolated thrombocytopenia initially. He experienced recurrent seizures with stable thrombocytopenia after the first seizures related to intracranial hemorrhage. He was identified a novel c.3452C>T mutation by targeted exome sequencing. If a patient with thrombocytopenia shows recurrent seizures as well as renal, hearing, visual symptoms, MHA should be suspected and the targeted exome sequencing is considered an effective diagnostic tool.

Genetic classification and confirmation of inherited platelet disorders: current status in Korea

Inherited platelet disorders (IPDs), which manifest as primary hemostasis defects, often underlie abnormal bleeding and a family history of thrombocytopenia, bone marrow failure, hematologic malignancies, undefined mucocutaneous bleeding disorder, or congenital bony defects. Wide heterogeneity in IPD types with regard to the presence or absence of thrombocytopenia, platelet dysfunction, bone marrow failure, and dysmegakaryopoiesis is observed in patients. The individual processes involved in platelet production and hemostasis are genetically controlled; to date, mutations of more than 50 genes involved in various platelet biogenesis steps have been implicated in IPDs. Representative IPDs resulting from defects in specific pathways, such as thrombopoietin/MPL signaling; transcriptional regulation; granule formation, trafficking, and secretion; proplatelet formation; cytoskeleton regulation; and transmembrane glycoprotein signaling are reviewed, and the underlying gene mutations are discussed based on the National Center for Biotechnology Information database and Online Mendelian Inheritance in Man accession number. Further, the status and prevalence of genetically confirmed IPDs in Korea are explored based on searches of the PubMed and KoreaMed databases. IPDs are congenital bleeding disorders that can be dangerous due to unexpected bleeding and require genetic counseling for family members and descendants. Therefore, the pediatrician should be suspicious and aware of IPDs and perform the appropriate tests if the patient has unexpected bleeding. However, all IPDs are extremely rare; thus, the domestic incidences of IPDs are unclear and their diagnosis is difficult. Diagnostic confirmation or differential diagnoses of IPDs are challenging, time-consuming, and expensive, and patients are frequently misdiagnosed. Comprehensive molecular characterization and classification of these disorders should enable accurate and precise diagnosis and facilitate improved patient management.

[Rare diseases recognizable from blood smears]

The examination of peripheral blood smears is not only essential for the differential diagnostics of hematological diseases but can also provide important indications for general internal diseases, infections, hereditary diseases and poisoning. By the systematic analysis of a blood smear for alterations to thrombocytes, erythrocytes and leukocytes, a blood smear investigation can make a decisive contribution to the formulation of a diagnosis. In this way evidence of rare diseases can also be gained when taking the corresponding clinical findings into consideration.

Epidural anesthesia for labor and delivery in a patient with May-Hegglin anomaly: a case report

We report a case of May-Hegglin anomaly (MHA) in a woman who had a successful labor and delivery under epidural anesthesia. MHA is an inherited thrombocytopenia easily misdiagnosed as idiopathic (immune) thrombocytopenic purpura (ITP). Early and appropriate diagnosis of MHA during pregnancy is essential for optimal maternal and neonatal delivery outcome. Additionally, it can avoid unnecessary diagnostic studies, such as bone marrow aspiration and biopsy, and even harmful therapies with corticosteroids, immunosuppressive agents, and splenectomy. Consequently, the most serious impacts of this disease are iatrogenic managements due to misdiagnosis. It seems that in patients with MHA, adequate clinical coagulation is far more dependent on adequate platelet function than any particular platelet count. The diagnosis of MHA may pose a challenge for clinicians managing pregnant women with thrombocytopenia.

Inherited thrombocytopenias: the beat goes on

In this issue of Blood, Bottega et al document mutations in ACTN1, which encodes the cytoskeletal protein α-actinin 1, in 10 of 239 consecutive probands with an inherited thrombocytopenia--making ACTN1 an important cause of familial thrombocytopenia.

Historical perspective and future directions in platelet research

Platelets are a remarkable mammalian adaptation that are required for human survival by virtue of their ability to prevent and arrest bleeding. Ironically, however, in the past century, the platelets' hemostatic activity became maladaptive for the increasingly large percentage of individuals who develop age-dependent progressive atherosclerosis. As a result, platelets also make a major contribution to ischemic thrombotic vascular disease, the leading cause of death worldwide. In this brief review, I provide historical descriptions of a highly selected group of topics to provide a framework for understanding our current knowledge and the trends that are likely to continue into the future of platelet research. For convenience, I separate the eras of platelet research into the "Descriptive Period" extending from ~1880-1960 and the "Mechanistic Period" encompassing the past ~50 years since 1960. We currently are reaching yet another inflection point, as there is a major shift from a focus on traditional biochemistry and cell and molecular biology to an era of single molecule biophysics, single cell biology, single cell molecular biology, structural biology, computational simulations, and the high-throughput, data-dense techniques collectively named with the "omics postfix". Given the progress made in understanding, diagnosing, and treating many rare and common platelet disorders during the past 50 years, I think it appropriate to consider it a Golden Age of Platelet Research and to recognize all of the investigators who have made important contributions to this remarkable achievement..

Renal manifestations of patients with MYH9-related disorders

MYH9-related disorders are a group of autosomal, dominantly inherited disorders caused by mutations of the MYH9 gene, which encodes the non-muscle myosin heavy chain IIA (NMMHC-IIA). May-Hegglin anomaly and Sebastian, Fechtner, and Epstein syndromes belong to this group. Macrothrombocytopenia is a common characteristic associated with MYH9-related disorders, and basophilic cytoplasmic inclusion bodies in leukocytes (Döhle-like bodies), deafness, cataracts, and glomerulopathy are also found in some patients. In this study, renal manifestations of 7 unrelated Korean patients with MYH9-related disorders were analyzed. Of a total of 7 patients, 4 had disease-related family histories. One familial case had a mutation in the tail domain of NMMHC-IIA and showed milder renal involvement with preserved renal function by his 30s. Among the 3 familial cases without renal involvement, 2 had mutations in the tail domain of NMMHC-IIA and 1 had a mutation in the motor domain. The remaining 3 sporadic cases had severe renal involvement with rapid progression to end-stage renal disease and mutations located in the motor domain. In summary, mutations in the motor domain of NMMHC-IIA and negative family history were associated with severe renal involvement in patients with MYH9-related disorders. These results are in agreement with those of previous reports.

Genomewide linkage scan for diabetic renal failure and albuminuria: the FIND study

BACKGROUND

Diabetic nephropathy (DN) is a leading cause of mortality and morbidity in patients with type 1 and type 2 diabetes. The multicenter FIND consortium aims to identify genes for DN and its associated quantitative traits, e.g. the urine albumin:creatinine ratio (ACR). Herein, the results of whole-genome linkage analysis and a sparse association scan for ACR and a dichotomous DN phenotype are reported in diabetic individuals.

METHODS

A genomewide scan comprising more than 5,500 autosomal single nucleotide polymorphism markers (average spacing of 0.6 cM) was performed on 1,235 nuclear and extended pedigrees (3,972 diabetic participants) ascertained for DN from African-American (AA), American-Indian (AI), European-American (EA) and Mexican-American (MA) populations.

RESULTS

Strong evidence for linkage to DN was detected on chromosome 6p (p = 8.0 × 10(-5), LOD = 3.09) in EA families as well as suggestive evidence for linkage to chromosome 7p in AI families. Regions on chromosomes 3p in AA, 7q in EA, 16q in AA and 22q in MA displayed suggestive evidence of linkage for urine ACR. The linkage peak on chromosome 22q overlaps the MYH9/APOL1 gene region, previously implicated in AA diabetic and nondiabetic nephropathies.

CONCLUSION

These results strengthen the evidence for previously identified genomic regions and implicate several novel loci potentially involved in the pathogenesis of DN.

Single-step separation of platelets from whole blood coupled with digital quantification by interfacial platelet cytometry (iPC)

We report the efficient single-step separation of individual platelets from unprocessed whole blood, enabling digital quantification of platelet function using interfacial platelet cytometry (iPC) on a chip. iPC is accomplished by the precision micropatterning of platelet-specific protein surfaces on solid substrates. By separating platelets from whole blood using specific binding to protein spots of a defined size, iPC implements a simple incubate-and-rinse approach, without sample preparation, that enables (1) the study of platelets in the physiological situation of interaction with a protein surface, (2) the choice of the number of platelets bound on each protein spot, from one to many, (3) control of the platelet-platelet distance, including the possibility to study noninteracting single platelets, (4) digital quantification (counting) of platelet adhesion to selected protein matrices, enabling statistical characterization of platelet subpopulations from meaningfully large numbers of single platelets, (5) the study of platelet receptor expression and spatial distribution, and (6) a detailed study of the morphology of isolated single platelets at activation levels that can be manipulated. To date, we have demonstrated 1-4 of the above list. Platelets were separated from whole blood using iPC with fibrinogen, von Willebrand factor (VWF), and anti-CD42b antibody printed "spots" ranging from a fraction of one to several platelet diameters (2-24 μm). The number of platelets captured per spot depends strongly on the protein matrix and the surface area of the spot, together with the platelet volume, morphology, and activation state. Blood samples from healthy donors, a May-Hegglin-anomaly patient, and a Glanzmann's Thrombasthenia patient were analyzed via iPC to confirm the specificity of the interaction between protein matrices and platelets. For example, the results indicate that platelets interact with fibrinogen spots only through the fibrinogen receptor (αIIbβ3) and, relevant to diagnostic applications, platelet adhesion correlates strongly with normal versus abnormal platelet function. A critical function of platelets is to adhere to regions of damage on blood vessel walls; in contrast to conventional flow cytometry, where platelets are suspended in solution, iPC enables physiologically relevant platelet bioassays based on platelet/protein-matrix interactions on surfaces. This technology should be inexpensive to implement in clinical assay format, is readily integrable into fluidic microdevices, and paves the way for high-throughput platelet assays from microliter volumes of whole blood.

Patients with Epstein-Fechtner syndromes owing to MYH9 R702 mutations develop progressive proteinuric renal disease

Recent linkage analyses of nondiabetic African-American patients with focal segmental glomerulosclerosis (FSGS) have identified MYH9, encoding nonmuscle myosin heavy chain IIA (NMMHC-IIA), as a gene having a critical role in this disease. Abnormalities of the MYH9 locus also underlie rare autosomal dominant diseases such as May-Hegglin anomaly, and Sebastian, Epstein (EPS), and Fechtner (FTNS) syndromes that are characterized by macrothrombocytopenia and cytoplasmic inclusion bodies in granulocytes. Among these diseases, patients with EPS or FTNS develop progressive nephritis and hearing disability. We analyzed clinical features and pathophysiological findings of nine EPS-FTNS patients with MYH9 mutations at the R702 codon hot spot. Most developed proteinuria and/or hematuria in early infancy and had a rapid progression of renal impairment during adolescence. Renal histopathological findings in one patient showed changes compatible with FSGS. The intensity of immunostaining for NMMHC-IIA in podocytes was decreased in this patient compared with control patients. Thus, MYH9 R702 mutations display a strict genotype-phenotype correlation, and lead to the rapid deterioration of podocyte structure. Our results highlight the critical role of NMMHC-IIA in the development of FSGS.

Epstein syndrome presenting as renal failure in young patients

Two young Chinese patients presented with renal failure and thrombocytopenia. Further investigations showed the presence of large platelets and high-frequency sensorineural hearing deficit. Genetic studies confirmed mutations in the gene encoding the myosin heavy chain (MYH-9), and Epstein Syndrome was diagnosed. One patient underwent deceased-donor kidney transplantation with satisfactory graft function. Epstein Syndrome is a rare genetic disorder with autosomal dominant inheritance. Clinicians should be aware of this entity when a young patient presents with renal failure and thrombocytopenia.

Anesthetic management of seven deliveries in three sisters with the May-Hegglin anomaly

May-Hegglin anomaly is a rare genetic hematological disorder characterized by thrombocytopenia, but platelet function is usually normal. Three sisters with May-Hegglin anomaly and thrombocytopenia (platelet counts 14,000-100,000/mm(3)) were given neuraxial anesthesia for a total of 7 deliveries, 5 vaginal and 2 cesarean. None of the women had complications and no blood products were transfused.

MYH9 is associated with nondiabetic end-stage renal disease in African Americans

As end-stage renal disease (ESRD) has a four times higher incidence in African Americans compared to European Americans, we hypothesized that susceptibility alleles for ESRD have a higher frequency in the West African than the European gene pool. We carried out a genome-wide admixture scan in 1,372 ESRD cases and 806 controls and found a highly significant association between excess African ancestry and nondiabetic ESRD (lod score = 5.70) but not diabetic ESRD (lod = 0.47) on chromosome 22q12. Each copy of the European ancestral allele conferred a relative risk of 0.50 (95% CI = 0.39-0.63) compared to African ancestry. Multiple common SNPs (allele frequencies ranging from 0.2 to 0.6) in the gene encoding nonmuscle myosin heavy chain type II isoform A (MYH9) were associated with two to four times greater risk of nondiabetic ESRD and accounted for a large proportion of the excess risk of ESRD observed in African compared to European Americans.

Identification and characterization of the first large deletion of the MYH9 gene associated with MYH9 disorders

MYH9 disorders are autosomal dominant macrothrombocytopenias with leukocyte inclusion bodies. Single point mutations in the protein-coding sequence of the MYH9 gene are the most common cause. So far no large gene deletion/insertion and splicing defects have been reported. Conventional DNA sequencing of each MYH9-coding exon showed no abnormalities in a patient. Reverse transcription- polymerase chain reaction (PCR) amplification and sequencing of neutrophil mRNA identified an inframe deletion of exon 25. Further long-range PCR amplification of genomic DNA revealed a deletion of 1220 nucleotides including entire exon 25. Immunoblot analysis showed a small, abnormal protein in neutrophils but not in platelets. This is the first report of a large deletion of the MYH9 gene leading to the development of MYH9 disorders.