Inherited platelet disorders

Outcomes in Mild to Moderate Isolated Thrombocytopenia

OBJECTIVES

Incidental isolated mild to moderate thrombocytopenia is a frequent laboratory finding prompting a referral to pediatric hematology-oncology. We tested the hypothesis that patients with isolated asymptomatic mild thrombocytopenia would not progress to require an intervention from a pediatric hematologist-oncologist.

METHODS

This is a 5-year retrospective review of 113 patients referred to pediatric hematology-oncology for isolated thrombocytopenia. Initial, lowest, and current platelet counts along with clinical course and need for interventions were recorded. Thrombocytopenia was categorized as mild (platelet count: 101-140 × 10³/μL), moderate (platelet count: 51-100 × 10³/μL), severe (platelet count: 21-50 × 10³/μL), and very severe (platelet count: ≤20 × 10³/μL).

RESULTS

Eight of 48 patients (17%) referred for initial mild isolated thrombocytopenia progressed to moderate thrombocytopenia at 1 visit. At present, 2 of these patients have moderate thrombocytopenia, 17 remain with mild thrombocytopenia, and 29 patients have resolved thrombocytopenia. Nine of 65 patients (14%) referred for moderate thrombocytopenia progressed to severe or very severe thrombocytopenia on 1 occasion. At present, no patients have severe thrombocytopenia, 18 remain with moderate thrombocytopenia, 14 improved to mild thrombocytopenia, and 33 have resolved thrombocytopenia. Only 3 patients required interventions from a hematologist, whereas 10 patients required therapy from other subspecialties.

CONCLUSIONS

We only identified 3 patients (3%) with mild to moderate thrombocytopenia who required an intervention from a hematologist to improve platelet counts. Patients with isolated mild thrombocytopenia with a normal bleeding history and physical examination findings frequently have normalized their platelet counts within 1 month.

Diagnostic approach to platelet function disorders

Platelet disorders are common bleeding disorders, with a variety of congenital and acquired causes. The diagnostic evaluation of platelet disorders challenges both clinicians and clinical laboratories, as testing for these conditions is complex, not well standardized and time consuming. An understanding of normal platelet function has provided insights on the pathogenesis of many platelet function disorders. Knowledge of the key features of platelet disorders aids their diagnostic assessment. Tests for aggregation, secretion and dense granule defects continue to be the most helpful for the evaluation of suspected platelet function disorders.

Inherited platelet function disorders versus other inherited bleeding disorders: an Indian overview

Inherited deficiencies of plasma proteins involved in blood coagulation generally lead to lifelong bleeding disorders, whose severity is directly proportional to the degree of factor deficiency. Platelet and other coagulation factors play an important role in the haemostasis mechanism. We attempted to study the prevalence of inherited platelet function disorders (PFDs) and correlate with other coagulation factor disorders in the Indian population. Patients with PFDs and other coagulation factor disorders who presented at our hospital during the 5 year period (from January, 2001 to December, 2005) were the subjects of the study. A total of 1576 patients were diagnosed to have congenital bleeding disorders including PFDs, von Willebrand disease, haemophilia A and B and rare coagulation disorder cases. Haemophilia A (HA) was the most common and was seen in 52.31% of the patients followed by total PFDs seen in 27.77% of the patients. Based on severity of the disease, the results of PFDs were highly significant when compared to haemophilia and von Willebrand disease (VWD) (p=0.000). Severity was found higher in HA (77.8%) followed by HB (69.6%) and was found lower for PF3 availability defect (9.0%). It has been concluded that the prevalence of PFDs is relatively low as compared to coagulation factors related disorder and also it has been established that type-1 VWD is relatively less frequent in India as compared to the West.

Diagnostic approach to inherited bleeding disorders

The appropriate development of hemostasis encompasses a delicate equilibrium between anti- and prothrombotic forces developing during three distinct phases (primary hemostasis, coagulation and fibrinolysis) that are closely linked to each other and precisely regulated to close vessel wounds, promote vascular healing and maintain vessel patency. Imbalance in each of these systems produces either hemorrhagic or thrombotic disorders. Inherited bleeding disorders, caused by quantitative or qualitative alterations of either platelets or plasma proteins involved in blood coagulation and fibrinolysis, may lead to serious and lifelong bleeding conditions, the severity of which is inversely associated with the degree of the underlying defect. Rapid and reliable identification of these pathologies is worthy of focus to allow the adoption of appropriate substitutive or supportive antihemorrhagic therapies. Evaluation of the hemorrhage-prone patient requires careful recording of the medical history, attention to pertinent physical findings and the discretionary use of laboratory resources. Owing to the low diagnostic efficiency of clinical history and examination, an appropriate and reliable laboratory approach, encompassing first- and second-line testing, is essential to screen, diagnose and monitor patients with bleeding diatheses. As both the analytical sensitivity and responsiveness of traditional coagulation assays to different abnormalities differ widely, each laboratory should establish individual guidelines based on field experience and on reagent and instrument characteristics. Emerging evidence indicates that the implementation of global coagulation tests, such as the thrombin generation assay and clot waveform analysis, would provide additional information for clinical decision-making for patients with inherited bleeding disorders.

Risk of excessive bleeding associated with marginally low von Willebrand factor and mild platelet dysfunction

BACKGROUND

Bleeding symptoms are so commonly reported that it is not known whether they associate causally or coincidentally with mild but measurable primary hemostatic defects. OBJECTIVES/PATIENTS/METHODS: In order to evaluate if the mild primary hemostatic defects are truly causative of increased bleeding symptoms, we surveyed a population of healthy teenagers for bleeding symptoms. Using a case-control approach, we then estimated the risk of excessive bleeding associated with low von Willebrand factor (defined as VWF below the 5th percentile of a normal reference population), and with mild platelet dysfunction [PD, defined as concurrent reduced platelet aggregation responses to two agonists (adenosine diphosphate and epinephrine)].

RESULTS

Excessive bleeding was present in 63 out of 809 teenagers (7.8%). Among the 49 cases who were tested for VWF, low values by three measures were more commonly present than in 166 controls, specifically, ristocetin cofactor (RCo) activity [20.4% vs. 5.4%, odds ratio (OR) 4.5], collagen binding (14.3% vs. 4.2%, OR 3.8), and antigen level (20.4% vs. 6.0%, OR 4.0). The low RCo values ranged from 35 to 45 U dL(-1) except for a single case with 26 U dL(-1). Of the 47 teenagers with excessive bleeding who underwent platelet aggregation studies, reduced responses were more common than in controls (12.8% vs. 4.4%, OR 3.2). Twenty-nine per cent of cases with excessive bleeding had either low RCo or PD.

CONCLUSION

Almost one in three teenagers who report excessive bleeding is likely to have a measurable hemostatic disturbance manifested either by marginally low VWF (by three measures) or by mild PD.

Coagulation Defects

The present understanding of the coagulation process emphasizes the final common pathway and the proteolytic systems that result in the degradation of formed clots and the prevention of unwanted clot formations, as well as a variety of defense systems that include tissue repair, autoimmune processes, arteriosclerosis, tumor growth, the spread of metastases, and defense systems against micro-organisms. This article discusses diagnosis and management of some of the most common bleeding disorders. The goals are to provide a simple guide on how best to manage patients afflicted with congenital or acquired clotting abnormalities during the perioperative period, present a brief overview of the methods of testing and monitoring the coagulation defects, and discuss the appropriate pharmacologic or blood component therapies for each disease.

The obstetric and gynaecological management of women with inherited bleeding disorders - review with guidelines produced by a taskforce of UK Haemophilia Centre Doctors' Organization

The gynaecological and obstetric management of women with inherited coagulation disorders requires close collaboration between obstetrician/gynaecologists and haematologists. Ideally these women should be managed in a joint disciplinary clinic where expertise and facilities are available to provide comprehensive assessment of the bleeding disorder and a combined plan of management. The haematologist should arrange and interpret laboratory tests and make provision for appropriate replacement therapy. These guidelines have been provided for healthcare professionals for information and guidance and it is also intended that they are readily available for women with bleeding disorders.

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.

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.

Bleeding risks associated with inheritance of the Quebec platelet disorder

Quebec platelet disorder (QPD) is an autosomal dominant bleeding disorder associated with increased urokinase-type plasminogen activator in platelets and α-granule protein degradation. To determine bleeding risks and common manifestations of QPD, a history questionnaire was developed and administered to 127 relatives in a family with QPD. Data entry was done blinded to affected and unaffected status, determined by assays for platelet urokinase-type plasminogen activator (u-PA) and fibrinogen degradation. Odds ratios (ORs), with 95% confidence intervals (CIs), were determined for items queried. Summative bleeding scores for each individual were calculated using items with OR more than 1. Mean ages (34 years; range, 1-89 years) were similar for affected (n = 23) and unaffected (n = 104) family members. Affected individuals had higher mean bleeding scores (P < .0001) and a much higher likelihood (OR > 20) of having bleeding that led to lifestyle changes, bruises that spread lower or as large or larger than an orange or both, joint bleeds, bleeding longer than 24 hours after dental extractions or deep cuts, and received or been recommended other treatments (fibrinolytic inhibitors) for bleeding. Individuals with QPD and exposure(s) to hemostatic challenges had experienced excessive bleeding only when fibrinolytic inhibitors had not been used. These data illustrate that QPD is associated with increased risks of bleeding that can be modified by fibrinolytic inhibitors.