Inherited thrombocytopenia and platelet disorders with germline predisposition to myeloid neoplasia

Advances in molecular genetic sequencing techniques have contributed to the elucidation of previously unknown germline mutations responsible for inherited thrombocytopenia (IT). Regardless of age of presentation and severity of symptoms related to thrombocytopenia and/or platelet dysfunction, a subset of patients with IT are at increased risk of developing myeloid neoplasms during their life time, particularly those with germline autosomal dominant mutations in RUNX1, ANKRD26, and ETV6. Patients may present with isolated thrombocytopenia and megakaryocytic dysmorphia or atypia on baseline bone marrow evaluation, without constituting myelodysplasia (MDS). Bone marrow features may overlap with idiopathic thrombocytopenic purpura (ITP) or sporadic MDS leading to misdiagnosis. Progression to myelodysplastic syndrome/ acute myeloid leukemia (MDS/AML) may be accompanied by progressive bi‐ or pancytopenia, multilineage dysplasia, increased blasts, cytogenetic abnormalities, acquisition of bi‐allelic mutations in the underlying gene with germline mutation, or additional somatic mutations in genes associated with myeloid malignancy. A subset of patients may present with MDS/AML at a young age, underscoring the growing concern for evaluating young patients with MDS/AML for germline mutations predisposing to myeloid neoplasm. Early recognition of germline mutation and predisposition to myeloid malignancy permits appropriate treatment, adequate monitoring for disease progression, proper donor selection for hematopoietic stem cell transplantation, as well as genetic counseling of the affected patients and their family members. Herein, we describe the clinical and diagnostic features of IT with germline mutations predisposing to myeloid neoplasms focusing on mutations involving RUNX1, ANKRD26, and ETV6.     

Investigation of platelet function and platelet disorders using flow cytometry

Patients with thrombocytopenia or platelet disorders are at risk of severe bleeding. We report the development and validation of flow cytometry assays to diagnose platelet disorders and to assess platelet function independently of platelet count. The assays were developed to measure glycoprotein levels (panel 1) and platelet function (panel 2) in sodium citrated blood. Twenty healthy volunteers and five patients diagnosed with different platelet disorders were included. Glycoprotein expression levels of the receptors Ia, Ib, IIb, IIIa and IX were measured and normalised with forward scatter (FS) as a measurement of platelet size. Platelet function was assessed by CD63, P-selectin and bound fibrinogen in response to arachidonic acid, adenosine diphosphate (ADP), collagen-related peptide, ristocetin and thrombin receptor-activation peptide-6. All patients except one with suspected δ-granule defect showed aberrant levels of glycoproteins in panel 1. Glanzmann's thrombasthenia and genetically verified Bernard–Soulier syndrome could be diagnosed using panel 1. All patients showed reduced platelet function according to at least one agonist. Using panel 2 it was possible to diagnose Bernard–Soulier syndrome, δ-granule defect and GPVI disorder. By combining the two assays, we were able to diagnose different platelet disorders and investigate platelet function independent of platelet count.     

Use of DDAVP in inherited and acquired platelet dysfunction

Twenty-one patients with prolonged bleeding times secondary to inherited disorders of platelet function and eight patients with prolonged bleeding times secondary to acquired platelet dysfunction were given 0.3 micrograms per kilogram of DDAVP, 1-deamino-8-D-arginine vasopressin, intravenously. Sixteen of twenty-two DDAVP trials in patients with inherited platelet dysfunction (73%) and seven of the nine DDAVP trials in patients with acquired platelet dysfunction (78%) resulted in normalization or shortening of the prolonged bleeding times by at least 4 min. The bleeding time response did not correlate with changes in the levels of von Willebrand factor (vWf) antigen or ristocetin cofactor activity, nor was it associated with changes in vWf multimeric analysis or in vitro platelet aggregations following the administration of DDAVP. Shortening of the bleeding time with DDAVP was seen in patients with a failure to release/storage pool type defect, thromboxane synthesis type defect, Bernard-Soulier syndrome, Glanzmann's thrombasthenia, the May-Hegglin anomaly, liver disease, nonuremic renal disease, myelofibrosis, and Tangier's disease.     

Thrombopoietin is synergistic with other hematopoietic growth factors and physiologic platelet agonists for platelet activation in vitro

Thrombopoietin (TPO) is the primary physiologic regulator of platelet production. The effect of TPO on platelet function, both alone and in combination with other hematopoietic growth factors, adenosine diphosphate (ADP), and epinephrine, was investigated using fluorescent-labeled antibodies to the activation-dependent antigen CD62 (P-selectin) and flow cytometry. TPO stimulated CD62 expression on normal human platelets, and this expression was completely inhibited by the soluble extracellular domain of the TPO receptor, MPL. The growth factors granulocyte colony-stimulating factor (G-CSF) and erythropoietin (EPO), but not interleukin-3 (IL-3) or stem-cell factor (SCF), also stimulated platelet activation. The combination of EPO, SCF, ADP, and epinephrine with TPO were synergistic for platelet CD62 expression. These data further support a role for TPO in modulating platelet function. Am. J. Hematol. 54:225–232, 1997 © 1997 Wiley-Liss, Inc.     

Current status and future prospects for platelet function testing in the diagnosis of inherited bleeding disorders

Platelets play a crucial role in haemostasis by preventing bleeding at the site of vascular injury. Several defects in platelet morphology and function have been identified and described over the years. Although a range of methodologies is available to assess platelet function, a significant proportion of subjects with bleeding symptoms and normal coagulation parameters still appear to have normal results on platelet function testing. This might suggest that the reason for bleeding is multifactorial and is due to a combination of several minor defects in platelet function and/or other parts of the haemostatic system or might indicate that the currently available platelet function tests do not provide optimal diagnostic power. This review will summarize the established platelet function tests used for diagnosing inherited platelet abnormalities in adults and children, and discuss the newly developed methodologies as well as unmet challenges and potential areas for further improvement in this field.     

Inherited combined deficiency of factor V and factor VIII: report of a case with normal factor VIII antigen and ristocetin-induced platelet aggregation

A patient with inherited combined deficiency of factor V and factor VIII is reported, who demonstrated normal levels of factor VIII antigen and plasma cofactor for ristocetin-induced platelet aggregation. The relationship of this condition to classical hemophilia and von Willebrand's disease is discussed. The data presented suggest that multiple loci on at least 2 chromosomes are necessary for the normal expression of factor VIII activity.     

Autoimmune disorders of platelet function: systematic review of cases of acquired Glanzmann thrombasthenia and acquired delta storage pool disease

Acquired platelet function disorders (PFD) are rare bleeding diseases that should be suspected in all patients with unexplained mucocutaneous bleedings of recent onset, with no previous history of haemorrhages, and with normal coagulation test and platelet count. Drug-induced platelet function bleeding disorders are the most frequent PFDs and can easily be identified on the basis of recent administration of platelet-inhibiting drugs. Apart from these, the most challenging acquired PFDs are those caused by autoimmune mechanisms. In fact, demonstration of autoantibodies inhibiting platelet function may be difficult in most non-specialised centres. Among autoimmune PFDs (aPFDs), acquired Glanzmann thrombasthenia (aGT), which is caused by autoantibodies that bind to platelet αIIbβ3 integrin, inhibiting its function, is the most frequent. aGT can be associated with underlying haematological malignancies or autoimmune diseases but can also be idiopathic. More rarely, other immune-mediated PFDs can occur, such as acquired delta storage pool disease (aδSPD). Treatment of aPFDs must rely on the control of acute and chronic bleedings, treatment of the underlying disease in secondary forms, and immunosuppressive treatment for autoantibody reduction or eradication. aPFDs may completely resolve upon treatment of any underlying disease that may be present. In primary aPFDs, and in the majority of secondary forms, treatment relies on immunosuppressive therapies.Here we present a systematic review of previously described immune-mediated aGT and aδSPD cases. Clinical and laboratory characteristics, treatments for the control of bleedings and for the eradication of autoantibodies, and responses to treatments are also discussed. Although no guidelines are available for the management of these very rare conditions, presentation of all cases reported so far can help clinicians in the diagnosis and treatment of these life-threatening diseases.     

Genotype–phenotype relationship for six common polymorphisms in genes affecting platelet function from 286 healthy subjects and 160 patients with mucocutaneous bleeding of unknown cause

Polymorphisms affecting platelet receptors and intracellular proteins have been extensively studied in relation to their potential influence in thrombosis and haemorrhages. However, few reports have addressed their impact on platelet function, with contradictory results. Limitations of these studies include, among others, small number of patients, the platelet functional parameters analyzed and their known variability in the healthy population. We studied the effect of six polymorphisms [ ITGB3 1565T > C (HPA-1), GPIBA variable number tandem repeat and 524C > T (HPA-2), ITGA2 807C > T , ADRA2A 1780A > G , and TUBB1 Q43P ] on platelet function in 286 healthy subjects and their potential pathogenetic role in 160 patients with hereditary mucocutaneous bleeding of unknown cause. We found no effect of any of these polymorphisms on platelet aggregation, secretion, PFA-100^®, and thrombin generation in platelet rich plasma. Furthermore, patients and controls showed no significant differences in the frequency of any of these polymorphisms. Thus, our study demonstrated that polymorphisms in genes affecting platelet function do not influence significantly major platelet functions and appear irrelevant in the pathogenesis of bleeding disorders.     

肝富集转录因子对乙型肝炎病毒转录与复制的调控

乙肝病毒具有明显的嗜肝性.在非肝源乙肝病毒复制体系中,发现肝富集转录因子在HBV肝特异性复制过程中起重要作用.其中.肝富集转录因子HNF4和RXRα-PPARα是调节前基因组RNA转录和病毒复制所必需,是病毒嗜肝性的重要决定因素之一,而肝富集转录因子HNF3对HNF4和RXRα-PPARα介导的HBV转录和复制具有抑制作用.从而揭示HBV的嗜肝机制涉及HBV感染进入细胞和HBV基因转录复制两个水平的调控.     

糖尿病肾病大鼠肾小球叉头状转录因子O1的表达和作用

目的观察糖尿病肾病大鼠肾小球叉头状转录因子O1（FoxO1）的表达,探讨其与糖尿病肾病发生、发展的关系。方法8周龄健康雄性sD大鼠30只,链脲佐菌素（STZ）诱导建立糖尿病大鼠模型,采用随机数字表法分为糖尿病组（13只,普通饲料连续喂养4周）和糖尿病肾病组（13只,普通饲料连续喂养12周）。选取健康同龄大鼠18只作为正常对照组（NC组）。4、12周末检测体质量（BW）、血糖（BG）、血肌酐（Scr）、尿素氮（BUN）、24h尿蛋白（UPro／24h）及尿白蛋白定量（UAIb）。处死动物后计算肾重指数（KI）;分光光度计测定大鼠肾皮质丙二醛（MDA）含量和总超氧化物歧化酶（SOD）活性;免疫组化法检测肾小球FoxO1蛋白、胶原Ⅳ及纤连蛋白水平;RT—PCR检测肾皮质Fox01mRNA水平;光镜及电镜下观察肾脏组织形态学变化。组间比较采用独立样本t检验。结果糖尿病肾病组肾皮质MDA蛋白、肾小球胶原Ⅳ和纤连蛋白水平显著高于糖尿病组[分别为（3．49±0．31）VS（2．34±0．28）nmol／mgProt,20．1±1．3VS10．1±1．0,10．6±1．3VS6．3±1．0,t值分别为9．290、20．967、9．119,均P〈0．05];糖尿病肾病组肾皮质SOD活性蛋白、Fox01mRNA表达水平明显低于糖尿病组[分别为（23±8）VS（43±6）U／mgProt,0．20±0．06VS0．35±0．05,t值分别为7．069、6．717,均P〈0．05]。FoxO1蛋白表达水平各组问比较无显著差异（均P〉0．05）。结论糖尿病肾病大鼠肾皮质FoxO1 mRNA表达水平降低,其机制可能通过下调其抗氧化靶基因使。肾脏氧化应激反应增强,从而参与糖尿病肾病发生发展的过程。