Unrelated hematopoietic stem cell transplantation for familial platelet disorder/acute myeloid leukemia with germline RUNX1 mutations

Germline mutations in RUNX1 result in rare autosomal-dominant familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML). As genetic analysis is becoming increasingly prevalent, the diagnosis rate of FPD/AML is expected to increase. In this report, we present two pedigrees, one diagnosed molecularly and another highly suspected to be FPD/AML, whose members both received allogeneic hematopoietic stem cell transplantation (HSCT). Both pedigrees had a family history of thrombocytopenia, platelet dysfunction, and hematological malignancies. One family inherited a frameshift mutation (p.P240fs) of RUNX1, a known pathogenic variant. Another family inherited a point mutation (p.G168R) in the runt-homology domain, the clinical significance of which is uncertain at this point. As this mutation was completely absent from all population databases and had a relatively high REVEL score of 0.947, we thought that it would be dangerous to ignore its possible pathogenicity. Consequently, we avoided choosing HSCT donors from relatives of both families and performed HSCT from unrelated donors. In conclusion, our experience with two families of FPD/AML highlights the importance of searching for gene mutations associated with germline predisposition and indicates the necessity of developing a donor coordination system for FPD/AML patients, as well as a support system for families.

Treatment of Inherited Platelet Disorders: Current Status and Future Options

Inherited platelet disorders (IPDs) comprise a heterogeneous group of entities that manifest with variable bleeding tendencies. For successful treatment, the underlying platelet disorder, bleeding severity and location, age, and sex must be considered in the broader clinical context. Previous information from the AWMF S2K guideline #086-004 (www.awmf.org) is evaluated for validity and supplemented by information of new available and future treatment options and clinical scenarios that need specific measures. Special attention is given to the treatment of menorrhagia and risk management during pregnancy in women with IPDs. Established treatment options of IPDs include local hemostatic treatment, tranexamic acid, desmopressin, platelet concentrates, and recombinant activated factor VII. Hematopoietic stem cell therapy is a curative approach for selected patients. We also provide an outlook on promising new therapies. These include autologous hematopoietic stem cell gene therapy, artificial platelets and nanoparticles, and various other procoagulant treatments that are currently tested in clinical trials in the context of hemophilia.

Progress in Hemostasis (Part 1): Improved Management of Inherited Platelet Disorders: Reality or Illusion?

Platelets are key drivers of hemostasis. Low platelet counts, dysfunction in platelet adhesion, and aggregation lead to increased bleeding tendency. Inherited platelet disorders (IPDs) form a highly heterogeneous group of rare diseases with variable bleeding tendency. IPDs may be associated with other signs and symptoms often referred to as "syndromic." The underlying genetic defect may prone patients to develop hematopoietic diseases such as leukemia. Over the last decade, accumulating knowledge in genetics has led to the detection of many "new" platelet disorders. However, still many patients with a well-described platelet dysfunction remain undetected until severe bleeding occurs.

Modeling genetic platelet disorders with human pluripotent stem cells: mega-progress but wanting more on our plate(let)

PURPOSE OF REVIEW

Megakaryocytes are rare hematopoietic cells that play an instrumental role in hemostasis, and other important biological processes such as immunity and wound healing. With the advent of cell reprogramming technologies and advances in differentiation protocols, it is now possible to obtain megakaryocytes from any pluripotent stem cell (PSC) via hematopoietic induction. Here, we review recent advances in PSC-derived megakaryocyte (iMK) technology, focusing on platform validation, disease modeling and current limitations.

RECENT FINDINGS

A comprehensive study confirmed that iMK can recapitulate many transcriptional and functional aspects of megakaryocyte and platelet biology, including variables associated with complex genetic traits such as sex and race. These findings were corroborated by several pathological models in which iMKs revealed molecular mechanisms behind inherited platelet disorders and assessed the efficacy of novel pharmacological interventions. However, current differentiation protocols generate primarily embryonic iMK, limiting the clinical and translational potential of this system.

SUMMARY

iMK are strong candidates to model pathologic mutations involved in platelet defects and develop innovative therapeutic strategies. Future efforts on generating definitive hematopoietic progenitors would improve current platelet generation protocols and expand our capacity to model neonatal and adult megakaryocyte disorders.

Inherited Platelet Disorders

Bleeding disorders due to platelet dysfunction are a common hematologic complication affecting patients, and typically present with mucocutaneous bleeding or hemorrhage. An inherited platelet disorder should be suspected in individuals with a suggestive family history and no identified secondary causes of bleeding. Genetic defects have been described at all levels of platelet activation, including receptor binding, signaling, granule release, cytoskeletal remodeling, and platelet hematopoiesis. Management of these disorders is typically supportive, with an emphasis on awareness, patient education, and anticipatory guidance to prevent future episodes of bleeding.

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.

Overview of Hemostasis and Thrombosis and Contribution of Laboratory Testing to Diagnosis and Management of Hemostasis and Thrombosis Disorders

Hemostasis is a complex and tightly regulated process whereby the body attempts to maintain a homeostatic balance to permit normal blood flow, without bleeding or thrombosis. When this balance is disrupted, due to trauma or underlying congenital bleeding or thrombotic disorders, clinical intervention may be required. To assist clinicians in diagnosing and managing affected patients, hemostasis laboratories offer an arsenal of tests, both routine (screening) and more specialized (diagnostic). In general, screening assays are used to screen for hemostasis-related disease or to monitor or measure the effect of anticoagulant therapy, which may be applied to treat patients with recent thrombosis or at risk of thrombosis. Diagnostic assays are used to diagnose or exclude specific hemostasis-related diseases, and in some cases, to monitor or measure the effect of anticoagulant therapy, or alternatively procoagulant therapy that may be applied to those at risk of bleeding. This chapter provides an overview of hemostasis and thrombosis with respect to laboratory tests that may be applied to affected patients.

Platelet-delivered therapeutics

We have proposed that modified platelets could potentially be used to correct intrinsic platelet defects as well as for targeted delivery of therapeutic molecules to sights of vascular injury. Ectopic expression of proteins within α-granules prior to platelet activation has been achieved for several proteins, including urokinase, factor (F) VIII, and partially for FIX. Potential uses of platelet-directed therapeutics will be discussed, focusing on targeted delivery of urokinase as a thromboprophylactic agent and FVIII for the treatment of hemophilia A patients with intractable inhibitors. This presentation will discuss new strategies that may be useful in the care of patients with vascular injury as well as remaining challenges and limitations of these approaches.

Inherited platelet function disorders: overview and disorders of granules, secretion, and signal transduction

Inherited disorders of platelet function are characterized by highly variable mucocutaneous bleeding manifestations. The platelet dysfunction arises by diverse mechanisms, including abnormalities in platelet membrane glycoproteins, granules and their contents, platelet signaling and secretion mechanisms: thromboxane production pathways and in platelet procoagulant activities. Platelet aggregation and secretion studies using platelet-rich plasma currently form the primary basis for the diagnosis of an inherited platelet dysfunction. In most such patients, the molecular and genetic mechanisms are unknown. Management of these patients needs to be individualized; therapeutic options include platelet transfusions, 1-desamino-8d-arginine vasopressin (DDAVP), recombinant factor VIIa, and antifibrinolytic agents.

[Desmopressin parenteral in patients with VWD1, VWD 2A and thrombocytopathy]

Desmopressin (DDAVP, Minirin® parenteral), which induces the release of von-Willebrand factor from endogenous stores, is indicated in von Willebrand disease type 1 (VWD 1). In the present study effectiveness of DDAVP was tested and side effects were recorded in patients with VWD 1, von Willebrand disease type 2 (VWD 2) or thrombocytopathy (TCP).

PATIENTS, METHODS

Subjects were analysed prior to and after Minirin parenteral infusion (0.4 μg/kg body weight (b.w.) over 60 minutes) for partial thromboplastin time (PTT, seconds), ADP/epinephrine triggered platelet-function analyzer (PFA-100) occlusion time (seconds), factor VIII activity (FVIII, %), VWF as ristocetin cofactor activity (VWF:RCo, %) and VWF antigen (VWF:Ag, %). Side effects of DDAVP during operative interventions were recorded per questionnaires by the patients.

RESULTS

The mean ± standard deviation dose (n = 165 patients) of Minirin parenteral administered was 0.37 ± 0.02 μg/kg b.w., most often upcoming dental operations (57%) necessitated testing. Coagulation parameters of patients with VWD 1 or TCP normalised in almost all patients, but only in approximately 50% of patients with VWD 2 respectively. Appraisal of effectiveness of Minirin parenteral as good was 96% in case of VWD 1 and 95 % in case of TCP. During minor surgeries (n = 23) in 91% of the patients no complications and in 2 patients (9%) postoperative haemorrhages without need for further interventions occurred, but 83% of the patients reported adverse reactions in the questionnaires, although Minirin parenteral was well tolerated by all patients during DDAVP efficacy tests.

CONCLUSION

Desmopressin is well tolerated and affective in patients with VWD 1 and thrombocytopathy.

Platelet disorders in adolescents

Acquired and inherited platelet disorders can present with bleeding symptoms during adolescence. Platelet disorders include disorders of platelet number and disorders of platelet function. In adolescent females with platelet disorders, menorrhagia is a common presenting bleeding symptom. Other associated bleeding symptoms are also primarily mucocutaneous, including epistaxis and bruising. Excessive bleeding may also occur after hemostatic challenges. Diagnosis of disorders of platelet function usually requires light transmission platelet aggregometry. Management of menorrhagia in the adolescent with platelet disorders requires both hematologic and gynecologic treatment.

[Progress in diagnostic evaluation of platelet function disorders]

Both for diagnosis of congenital and acquired platelet dysfunction as well as for therapy monitoring after application of platelet function inhibitors various methods have been established for evaluation of platelet function. In contrast to the gold standard of platelet function testing, the light transmission aggregometry in platelet rich plasma the Point-of-care (POC) analyzers allow fast analysis of platelet function without extensive laboratory work up. The conditions of the pre-analytical phase, however, are still of enormous importance in the prevention of medical errors. There is increasing clinical data in monitoring the effect of platelet aggregation inhibitors, showing that quantitative determination of the platelet function degree correlates with risk of increased bleeding or stent thrombosis. However, it is still unclear, which is the optimal test system, to predict the clinical outcome of these patients.

Methods for genetic modification of megakaryocytes and platelets

During recent decades there have been major advances in the fields of thrombosis and haemostasis, in part through development of powerful molecular and genetic technologies. Nevertheless, genetic modification of megakaryocytes and generation of mutant platelets in vitro remains a highly specialized area of research. Developments are hampered by the low frequency of megakaryocytes and their progenitors, a poor efficiency of transfection and a lack of understanding with regard to the mechanism by which megakaryocytes release platelets. Current methods used in the generation of genetically modified megakaryocytes and platelets include mutant mouse models, cell line studies and use of viruses to transform primary megakaryocytes or haematopoietic precursor cells. This review summarizes the advantages, limitations and technical challenges of such methods, with a particular focus on recent successes and advances in this rapidly progressing field including the potential for use in gene therapy for treatment of patients with platelet disorders.

[Acquired platelet function disorders: pathogenesis, classification, frequency, diagnosis, clinical management]

Given the high consumption of pharmacological agents in western societies, it is not surprising at all that drugs represent the most common cause of acquired platelet dysfunction. While acetylsalicylic acid, clopigogrel and integrin alphaIIbbeta3 (GPIIb-IIIa) receptor antagonists are well-known as prototypes of antiplatelet drugs, other widely used agents including non-steroidal anti-inflammatory drugs, antibiotics, serotonin reuptake inhibitors, and volume expanders can also impair platelet function and cause or aggravate haemorrhages. Besides pharmacological agents, certain clinical conditions are often associated with qualitative platelet disorders and bleeding diathesis. Consequently, in contrast to inherited platelet disorders, acquired platelet function defects are much more frequent in clinical practice and deserve special attention. Their pathogenesis is widespread and heterogeneous with various, sometimes overlapping abnormalities. Moreover, acquired platelet dysfunctions can occur at any age and range in severity from mild to life-threatening haemorrhages. Due to their heterogeneity, acquired platelet function disorders will be classified and discussed according to the underlying clinical setting or disease.

The prevalence of disorders of haemostasis in adolescents with menorrhagia referred to a haemophilia treatment centre

Menorrhagia at the time of menarche is relatively common and historically attributed primarily to immaturity of the pituitary-ovarian-uterine axis. Intuitively, a proportion of these patients should have an underlying disorder of haemostasis, given the 5-20% prevalence of von Willebrand's disease and the > or =20% prevalence of platelet dysfunction in light of recent epidemiological studies in menorrhagia, although the average age of the patients in those studies has been approximately 35 years. However, there are a few comprehensive studies in the adolescent population determining whether widespread haemostasis evaluation should be carried out in adolescents presenting with menorrhagia. A retrospective chart review study of disorders of haemostasis was carried out in 61 consecutive adolescent patients, ages 11-19 at the time of evaluation referred to the Hemophilia Treatment Center (HTC)/Hematology unit. The mean and median ages were 15 +/- 2.2 and 14 years (11, 19), respectively. Standard evaluation included complete blood count, prothrombin time, partial thromboplastin time, von Willebrand factor (VWF) levels and platelet aggregation. The proportion of patients with VWF deficiency was 22/61 (36%) [95% confidence interval (CI), 24-49%]; the proportion of patients with platelet aggregation abnormalities was 4/61 (7%) (95% CI, 2-16%). There was no difference in the frequency of additional muco-cutaneous bleeding symptoms. A relatively high proportion of adolescents are identified with an underlying disorder of haemostasis when referred to an HTC for evaluation of menorrhagia. This involves in part a selective referral bias, but underscores the role of the HTC in evaluating adolescents referred with menorrhagia for an underlying bleeding disorder, given the relatively high yield of haemostatic disorders detected in this setting.

Congenital Platelet Disorders

Congenital platelet disorders represent a rare group of diseases classified by either a qualitative or quantitative platelet defect. This article outlines the historical, clinical, laboratory, and genetic features of various inherited platelet disorders with attention given to updated information on disease classification, diagnosis, and genotypes. A separate discussion regarding management addresses the difficulty in treatment strategies, particularly in patients who develop alloimmunization to platelets.

The Evidence for the Use of Recombinant Human Activated Factor VII in the Treatment of Bleeding Patients With Quantitative and Qualitative Platelet Disorders

There are increasing reports suggesting that high-dose recombinant human activated factor VII (rFVIIa) is effective in the treatment and prevention of bleeding in patients with quantitative and qualitative platelet disorders. These clinical observations are supported by evidence that FVIIa binds weakly to activated platelet surface and at high concentration improves thrombin generation. In experimental models, this improved thrombin generation enhances platelet adhesion in thrombocytopenic conditions and enhances adhesion and aggregation of platelets lacking glycoprotein IIbIIIa (integrin alpha(IIb)beta(3)), characteristic of the qualitative platelet disorder Glanzmann thrombasthenia (GT). There is a need for clinical trials to confirm the safety and efficacy of rFVIIa in patients with various quantitative and qualitative platelet defects, either by itself or in combination with other hemostatic agents such as platelet transfusion. Pending the availability of such data, rFVIIa may be considered in severe bleeding in thrombocytopenia and GT patients with platelet antibodies and refractory to platelet transfusions and other standard treatments. An international survey suggests that rFVIIa at about 90 microg/kg every 2 hours for 3 or more doses could be used for GT patients with severe bleeding, but confirmation by larger studies is needed. For GT patients undergoing surgery and for treatment and prevention of bleeding in thrombocytopenic patients, the optimal rFVIIa regimen remains to be defined.

Platelet dysfunction and end-stage renal disease

Patients with end-stage renal disease (ESRD) develop hemostatic disorders mainly in the form of bleeding diatheses. Hemorrhage can occur at cutaneous, mucosal, or serosal sites. Retroperitoneal or intracranial hemorrhages also occur. Platelet dysfunction is the main factor responsible for hemorrhagic tendencies in advanced kidney disease. Anemia, dialysis, the accumulation of medications due to poor clearance, and anticoagulation used during dialysis have some role in causing impaired hemostasis in ESRD patients. Platelet dysfunction occurs both as a result of intrinsic platelet abnormalities and impaired platelet-vessel wall interaction. The normal platelet response to vessel wall injury with platelet activation, recruitment, adhesion, and aggregation is defective in advanced renal failure. Dialysis may partially correct these defects, but cannot totally eliminate them. The hemodialysis process itself may in fact contribute to bleeding. Hemodialysis is also associated with thrombosis as a result of chronic platelet activation due to contact with artificial surfaces during dialysis. Desmopressin acetate and conjugated estrogen are treatment modalities that can be used for uremic bleeding. Achieving a hematocrit of 30% improves bleeding time in ESRD patients.

A review of inherited platelet disorders with guidelines for their management on behalf of the UKHCDO

The inherited platelet disorders are an uncommon cause of symptomatic bleeding. They may be difficult to diagnose (and are likely to be under-diagnosed) and pose problems in management. This review discusses the inherited platelet disorders summarising the current state of the art with respect to investigation and diagnosis and suggests how to manage bleeding manifestations with particular attention to surgical interventions and the management of pregnancy.

Congenital platelet disorders: overview of their mechanisms, diagnostic evaluation and treatment

The bleeding problems associated with common and rare inherited platelet disorders illustrate the importance of platelets to normal haemostasis. At sites of injury, platelets normally adhere, undergo activation, secretion and aggregate formation, and they provide the membrane surface for the assembly of coagulation to generate thrombin. The causes of inherited disorders that alter platelet haemostatic functions are quite diverse, ranging from defects in receptors critical to platelet adhesion and aggregation, to defects in signalling molecules or in transcription factors important for production of functional platelets. The mechanisms of impaired platelet function are largely unknown for the more common disorders that alter platelet activation, secretion and the secondary wave of platelet aggregation. The diagnostic evaluation of congenital platelet disorders has been challenging as some 'platelet-type' bleeding symptoms, such as bruising, are quite common in the general population. Moreover, the diagnostic tests used by clinical laboratories to evaluate disorders of platelet function have not been standardized. In individuals recognized to have an inherited defect in platelet function, therapy is important for controlling and preventing bleeding episodes. Presently, there are a number of choices to consider for the management of bleeding symptoms, including menorrhagia. This paper reviews the causes, diagnostic evaluation and therapies for common and rare congenital platelet disorders.

Successful Bilateral Lung Transplantation for Pulmonary Fibrosis Associated With the Hermansky-Pudlak Syndrome

Hermansky-Pudlak syndrome (HPS) is a genetic disorder characterized by oculocutaneous albinism, a bleeding diathesis, and in a subset of patients, pulmonary fibrosis. Lung transplantation, the only curative therapy for pulmonary fibrosis, has not been previously reported as a successful treatment strategy for patients with HPS because the bleeding diathesis was thought to contraindicate major thoracic surgery. We successfully performed bilateral sequential lung transplantation in a patient with pulmonary fibrosis and HPS after transfusion of 6 units of platelets. Lung transplantation is a viable therapeutic option in patients with pulmonary fibrosis and only a mild bleeding diathesis associated with HPS.

Management of bleeding in a multi-transfused patient with positive HLA class I alloantibodies and thrombocytopenia associated with platelet dysfunction refractory to transfusion of cross-matched platelets

Thrombocytopenia is a common condition in the critical care setting. Repetitive platelet transfusion might lead to formation of alloantibodies. HLA class I and human platelet antigen antibodies can lead to transfusion-refractory thrombocytopenia. Transfusion of cross-matched platelets often is effective in these patients. We report on the successful use of recombinant activated factor VII in an acute bleeding situation in a multi-transfused patient presenting with positive HLA class I alloantibody status and thrombocytopenia associated with platelet dysfunction refractory to even transfusion of cross-matched platelets. The 41-year-old female patient developed HLA class I antibodies during former episodes of massive transfusion. Her former medical history was empty concerning hemorrhagic events. During this specific bleeding episode the patient suffered from intractable profuse bleeding from the nasopharynx and oral cavity. Global coagulation tests were within the normal range. Platelet dysfunction was confirmed by PFA100. Initially the patient responded well to Desmopressin infusion, but after 36 h she became thrombocytopenic and refractory to even transfusion of cross-matched platelets. Recombinant activated factor VII was chosen as the last resort. Two identical boli of 160 microg/kg NovoSeven each were injected via a central line within an interval of 3 h. After the first injection bleeding was significantly reduced and vasopressor support discontinued. After the second bolus bleeding completely ceased and did not reoccur. We did not observe any side effects. The pluripotent hemostatic agent recombinant activated factor VII might be a new option in the treatment of hemorrhagic episodes in patients presenting with this rare disorder, especially when the patient is refractory to cross-matched platelets or matched platelets are not available.

Diagnosis and Management of Mild Bleeding Disorders

Mild bleeding disorders are a common reason for a referral to a hematologist and these conditions can be challenging to evaluate. Recent research has highlighted that some bleeding symptoms are quite common in the general population and that there is clinical variability in symptom expression among individuals with defined bleeding problems. Moreover, bleeding risks for many bleeding disorders are unknown. This article reviews symptoms and problems that can be considered suspicious of a mild form of bleeding disorder and the diagnostic investigations useful to evaluate these problems. A stepwise approach is presented for the diagnostic evaluation, to allow detection of common and rare coagulation and fibrinolytic defects, and adequate assessments of potential von Willebrand factor and platelet problems. Some common problems in the diagnosis and management of mild bleeding problems are reviewed, including the common failure to establish a diagnosis with testing. An approach is proposed for translation of knowledge to patients who are challenged by mild bleeding problems.

Acquired disorders of platelet function

A qualitative abnormality of platelet function should be considered in patients with mucocutaneous bleeding in the absence of thrombocytopenia or von Willebrand disease. Antiplatelet drugs are the most common cause of acquired platelet disorders leading to bleeding. Uremia, hepatic cirrhosis, myeloma and related disorders, polycythemia vera, essential thrombocythemia, and cardiopulmonary bypass have long been recognized as clinical situations in which platelet dysfunction may contribute to bleeding. When an acquired platelet disorder is suspected, it is useful to examine platelet function by measuring the bleeding time, examining platelet-dependent closure time in a platelet function analyzer and performing platelet aggregometry. When a specific acquired platelet disorder is diagnosed, many treatment options are available including controlling the underlying disease, giving platelet transfusions and administering a hemostatic drug.

[Case of uremic platelet dysfunction]

The present case was a 59-year-old woman who underwent a right nephrectomy at 30 years of age, and in whom renal dysfunction occurred at 51 years of age. In November 199X, when her creatinine level reached 7 mg/dl, renal replacement therapy was recommended. She refused this therapy and began her own diet therapy, which consisted of taking only supplement beverage, but no food. Afterwards she became unable to do daily work, and entered our hospital in July of the next year. On admission, her bleeding time was over 10 minutes, but coagulation function tests showed normal values. Platelet function tests showed that coagulation with the addition of ADP was mildly decreased and that coagulation with the addition of aggregation was severely decreased. These data and her bleeding tendency improved with hemodialysis. Therefore, a diagnosis of aggregation non-responsive uremic platelet dysfunction was made. On admission, we were not able to insert a catheter for hemodialysis because of her severe bleeding tendency. A platelet transfusion was made so that we could insert the catheter without severe bleeding. However, this hemostatic effect lapsed after about five to six hours. Six hours after insertion of the catheter, oozing from the orifice of the catheter was seen and a red blood transfusion was necessary. Three days after beginning hemodialysis, the bleeding tendency was no longer seen. Her platelet function and coagulation test results also improved. We can make two conclusions regarding this case. The first is when the physician's medical strategy cannot be carried out due to uremic platelet dysfunction, a platelet transfusion can temporarily eliminate the bleeding tendency. The second is that the pathophysiology of uremic platelet dysfunction involves suppression of the primary step of platelet aggregation with collagen. Experience with the present case revealed the appropriate therapeutic strategy for the pathophysiology of uremic platelet dysfunction.

A practical concept for preoperative management of patients with impaired primary hemostasis

In a prospective study, 254 of 5649 unselected patients scheduled for surgery at our hospital were identified preoperatively as having either acquired (n=182) or inherited (n=72) impaired primary hemostasis (platelet dysfunction including von Willebrand disease). All patients were initially pretreated with desmopressin (DDAVP). Response to DDAVP or subsequent treatment(s) was defined as correction of any one of the abnormal PFA-100 platelet function tests. The non-responders were additionally treated with tranexamic acid or aprotinin; those with von Willebrand disease (vWD) received factor VIII concentrates with von Willebrand factor (vWF). Those still unresponsive to therapy received conjugated estrogens and, as a last attempt, a platelet transfusion. The administration of DDAVP led to a correction of platelet dysfunction in 229 of the 254 patients treated (90.2%). Tranexamic acid was effective in 12 of 16, aprotinin in 3 of 5, and factor VIII concentrates with vWF in all 4 patients with unresponsive to DDAVP. The remaining 6 patients were pretreated with conjugated estrogens, and 2 of these patients were additionally treated with platelet transfusion. The frequency of blood transfusion was lower, but not statistically significant (9.4% vs. 12.2%: p = 0.202) in preoperatively treated patients with impaired hemostasis than in patients without impaired hemostasis. In a retrospective group, the frequency of blood transfusion was statistically significant higher (89.3% vs. 11.3%: p < 0.001) in patients without preoperative correction of impaired hemostasis than in patients without impaired hemostasis. Preoperative correction of impaired primary hemostasis is possible in nearly all patients affected, and results in a reduction of homologous blood transfusions.

Gene therapy for platelet disorders: studies with Glanzmann's thrombasthenia

Current research aimed at correcting platelet defects are designed to further our knowledge in the use of hematopoietic stem cells for gene therapies of hemorrhagic disorders. Information gained from these studies may be directly applicable to treatment of disorders affecting platelets (e.g. Glanzmann's thrombasthenia, Bernard Soulier syndrome, gray platelet syndrome, and von Willebrand disease) as well as other disorders affecting distinct hematopoietic cell lineages. This work specifically addresses three questions: (i) can bone marrow stem cells be given sufficient genetic information to induce abnormal megakaryocytes to synthesize transgene products that help newly formed platelets to participate in normal hemostasis? (ii) can the newly synthesized receptor be maintained as a platelet-specific protein at therapeutic levels for a reasonable period of time? and (iii) will newly expressed proteins be tolerated by the immune system or become a target for B- and T-cell mediated immunity resulting in the premature destruction and clearing of the genetically altered megakaryocytes and platelets? Answers to these questions should indicate the feasibility of targeting platelets with genetic therapies that will in turn enable better management of patients with inherited bleeding disorders. The long-range benefit of this research will be an improved understanding of the regulation of protein expression during normal megakaryocytopoiesis, and the accumulation of additional scientific knowledge about normal platelet function and the way in which platelets and other cells recognize and interact with each other.

[Congenital and acquired platelet function disorders]

A survey is given on congenital and acquired platelet functional disorders. Congenital platelet functional disorders are extremely rare. Acquired platelet functional disorders are probably the most frequent disturbances of haemostasis. The knowledge of the defects leading to inherited platelet function disorders much improved our understanding of platelet function in general. Acquired platelet functional disorders are due to various diseases and drugs.

Inherited platelet disorders

Inherited platelet disorders are important causes of bleeding that can quantitatively and qualitatively alter platelets, impairing their function. The purpose of this review is to summarize current knowledge on the different types of inherited platelet disorders, their clinical and laboratory features, molecular genetic causes, and the therapies used in clinical practice to manage these conditions.

Platelet dosing

Many patients with thrombocytopenia require transfusion of platelet concentrates, and numerous factors may influence the observed response to transfusion. One factor gaining growing recognition in recent years is the consideration of the dose of platelets to administer. Review of the available data regarding the effect of platelet dose on transfusion outcome is presented in this summary, with attention to those situations that seem to require higher platelet doses. Appropriate dosing may not only improve the immediate response to transfusion, but also lead to a decrease in further platelet transfusion requirements. Recommendations supported by actual clinical data are outlined, but controlled studies are needed to determine optimum platelet doses for many common clinical situations.

Possible hemostatic effect of synthetic liposomes in experimental studies under flow conditions

BACKGROUND AND OBJECTIVES

The possibility of developing synthetic platelet substitutes is a subject of current interest. We explored the possible hemostatic effect of synthetic phospholipid incorporated in multilamellar vesicles (MLVs) or intermediate unilamellar vesicles (IUVs) using a well-characterized experimental system with circulating human thrombocytopenic blood (10 min, 250 s(-1)).

DESIGN AND METHODS

The ability of the liposomes containing different combinations of dipalmitoylphosphatidylcholine (DPPC), phosphatidylethanolamine (PE) and dipalmitoylphosphatidylserine (DPPS) to promote fibrin formation (%F) on the damaged subendothelium was morphometrically evaluated. Generation of thrombin in the system was monitored through prothrombin fragment F1+2 determination.

RESULTS

IUV liposomes containing DPPC, 1DPPS:9DPPC, 1DPPS:3DPPC, 1PE:1DPPC increased fibrin deposition on the subendothelium (53.87 +/- 11.0%; 39.76 +/- 6.75%; 40.69 +/- 10.54% and 32.22 +/- 7.35%, respectively vs. thrombocytopenic blood 11.5 +/- 1.2%; p<0.05), while 9PE:1DPPS IUV liposome failed to promote a procoagulant effect. MLV liposomes containing DPPC alone, 1DPPS:3DPPC and 1PE:1DPPC showed a positive effect on fibrin deposition (85.50 +/- 5.95%, 59.86 +/- 11.55% and 43.73 +/- 7.84% respectively; p<0.05). However, no effect was observed in those experiments performed with liposomes containing 3DPPS:1DPPC. After perfusion experiments, the coagulation system became activated, but differences were not statistically significant vs. control experiments, except for MLV liposomes containing DPPC alone (p<0.05).

INTERPRETATION AND CONCLUSIONS

These results confirm that, at an experimental level, liposomes containing phospholipids could potentially be used to improve hemostasis in patients with quantitative or qualitative platelet disorders.

Management of dental extractions in patients with bleeding disorders

OBJECTIVE

This study evaluated the effectiveness of a protocol to prevent bleeding after dental extraction in patients with hemophilia, von Willebrand's disease (VWD), or platelet disorders.

STUDY DESIGN

Replacement therapy was used in cases involving general anesthesia, and nerve trunk infiltration was used in patients with severe bleeding disorders (severe-to-moderate hemophilia or type 2-3 VWD). Desmopressin was used in good responders with mild hemophilia A, type 1 VWD, and platelet disorders. Local hemostatic measures and antifibrinolytic treatment were used systematically.

RESULTS

Ninety-three patients underwent 103 dental extractions; 2 of these patients had secondary bleeding requiring surgical hemostasis.

CONCLUSION

The indication for replacement therapy depended on the type of anesthesia that was used. Coagulation factor concentrates or desmopressin were necessary to avoid upper airway hematoma with general anesthesia or nerve trunk infiltration. With local anesthesia, substitutive treatment was indicated in patients with severe-to-moderate hemophilia and type 2-3 VWD. Inexpensive desmopressin was effective in those who responded well. Local hemostatic measures and antifibrinolytic treatment were performed systematically.

Platelet transfusion trigger in difficult patients

There is general consensus that a prophylactic pre-transfusion trigger at 10.000 platelets/microL in stable oncohematological patients is as safe as the traditional trigger of 20.000/microL, and that perioperative triggers at 50.000 and 100.000/microL are adequate in most surgical and neurosurgical conditions respectively. Guidelines on the trigger and other issues related to platelet transfusion can be found in nine documents published during 1987-2001 by the National Institutes of Health (NIH), the British Committee on Standardization in Hematology, the Royal College of Physicians of Edinburgh, the College of American Pathologists, the American Society of Anesthesiology and the American Society of Clinical Oncology (ASCO). Although consensus may be less evident on specific triggers for 'difficult' patients, the following triggers, listed by progressively increasing levels, have been proposed in the literature and have found general agreement: a stable oncohematological recipient: 10.000; lumbar puncture in a stable pediatric leukemic patient: 10.000; thrombocytopenia secondary to gpIIb/IIIa receptor inhibitors [corrected]:10.000; bone marrow aspiration and biopsy: 20.000; gastrointestinal endoscopy in cancer: 20.000-40.000; disseminated intravascular coagulation: 20.000-50.000; fiber-optic bronchoscopy in a bone marrow transplant recipient: 20.000-50.000; neonatal alloimmune thrombocytopenia: 30.000; major surgery in leukemia: 50.000; thrombocytopenia secondary to massive transfusion: 50.000; invasive procedures in cirrhosis: 50.000; cardiopulmonary bypass: 50.000-60.000; liver biopsy: 50.000-100.000; a nonbleeding premature infant: 60.000; neurosurgery: 100.000. The proposed values must be considered within the context of careful clinical evaluation of each individual patient, and attention should be given to the power of discrimination of platelet counters at low counts and to the prompt availability of good quality platelet products in the case of emergency.

Platelet disorders in pregnancy

Before the advent of automated cell counters, thrombocytopenia was looked for and identified after a clinical question. With automation, thrombocytopenia in pregnancy was commonly found, and with its commonality its clinical meaning went out of focus. For the majority of women, thrombocytopenia is benign and, as a marker of fetal thrombocytopenia, the value of maternal thrombocytopenia is almost non-existent.

May-Hegglin anomaly and pregnancy

A hypertensive patients with thrombocytopenia is reported who had two pregnancies complicated by preeclampsia and cesarean deliveries without hemorrhage. During her first pregnancy corticosteroids were given for presumed autoimmune thrombocytopenia. Thereafter she was splenectomised. Ten years later May-Hegglin anomaly and renal failure were diagnosed. One of her children had easy bruising.