Resource-Platelets

Complete plasminogen activator inhibitor type 1 (PAI-1) deficiency is an exceedingly rare autosomal recessive bleeding disorder previously identified and reported in a large Old Order Amish (OOA) kindred in Indiana [Fay et al. Blood 1997; 90: 204]. Mouse models suggest that proteolysis via the plasminogen activator/plasmin system plays a crucial role in reproduction including degradation of the follicular wall during ovulation, fertilization, embryo implantation and embryogenesis [Leonardsson et al., Proc Natl Acad Sci USA 1995; 92: 12446]. We report the obstetric, gynaecological and fertility histories of OOA individuals with homozygous PAI-1 deficiency. In this family, there are 10 affected members identified to date ranging in age between 10 and 32 years, including seven female patients and three male patients. To date, two women have achieved pregnancies without difficulty; however, they experienced antenatal bleeding and preterm labour. The early initiation and continuation of antifibrinolytic agents, Epsilon-aminocaproic acid or tranexamic acid, during the pregnancy and in the postpartum period, was believed to be successful in preventing major bleeding complications in our patients with complete PAI-1 deficiency.

Platelet counts of less than 150,000 per cubic millimeter during uncomplicated pregnancies are described as gestational thrombocytopenia if no alternative cause is identified. Platelet counts may be even lower in women with pregnancy-related complications. However, the occurrence and severity of thrombocytopenia throughout pregnancy are not defined.

Thrombocytopenia is a common hematologic issue encountered by obstetricians and hematologists, detected in about 10% of all pregnancies. In the vast majority of cases, the thrombocytopenia will be attributed to gestational thrombocytopenia (GT), where the thrombocytopenia is mild, does not necessitate active management, and does not introduce maternal or fetal bleeding risk. Although GT is common, the specific mechanism responsible for it is not known with certainty, and therefore, differentiating it from other causes of thrombocytopenia can be challenging. Previously proposed explanations for GT suggest that a decrease in platelet count is universal in pregnancy, and women diagnosed with GT are simply those with a baseline platelet count on the lower end of normal range. This concept is challenged in this review, and a possible mechanism for GT is proposed. Additionally, a framework for approaching the diagnosis and management of thrombocytopenia in pregnancy is presented.

Immune thrombocytopenia (ITP) is mediated by platelet autoantibodies that accelerate platelet destruction and inhibit their production. Most cases are considered idiopathic, whereas others are secondary to coexisting conditions. Insights from secondary forms suggest that the proclivity to develop platelet-reactive antibodies arises through diverse mechanisms. Variability in natural history and response to therapy suggests that primary ITP is also heterogeneous. Certain cases may be secondary to persistent, sometimes inapparent, infections, accompanied by coexisting antibodies that influence outcome. Alternatively, underlying immune deficiencies may emerge. In addition, environmental and genetic factors may impact platelet turnover, propensity to bleed, and response to ITP-directed therapy. We review the pathophysiology of several common secondary forms of ITP. We suggest that primary ITP is also best thought of as an autoimmune syndrome. Better understanding of pathogenesis and tolerance checkpoint defects leading to autoantibody formation may facilitate patient-specific approaches to diagnosis and management.

The two thrombopoietin receptor agonists (TPO-RA), eltrombopag and romiplostim, were licensed in the US for treatment of immune thrombocytopenia (ITP) in 2008 and, since then, their use has progressively increased around the world; they are currently used in more than 100 countries. The six largest randomized controlled trials conducted in ITP have used one of these two agents. All studies have demonstrated a platelet response rate between 50-90%, depending on the criteria used, with good safety and tolerability. TPO-RA were shown to be effective in reducing bleeding and the need for concomitant or rescue medication. Many other investigations of their mechanism of effect, prospective and retrospective trials, and studies focusing on toxicity have been performed widening our knowledge of these two agents. Initial concerns on issues such as myelofibrosis have not been confirmed. Only a small number of patients develop moderate-severe reticulin fibrosis and/or collagen fibrosis; however, these are usually reversed after discontinuation of TPO-RA. Studies indicate, however, that TPO-RA may increase the risk of venous thromboembolism. Both TPO-RA are currently approved in patients with chronic ITP aged >1-year who are refractory to at least one other treatment. Eltrombopag has acquired two additional indications: severe aplastic anemia refractory to first-line treatment and hepatitis C patients undergoing treatment with interferon-ribavirin. Despite these wide-ranging studies, important questions still need to be answered. This summary review on TPO-RA will summarize what is known regarding efficacy in ITP, evaluate safety concerns in more depth, and focus on the questions that remain.

ABSTRACT: Over the last decade, there have been numerous developments and changes in treatment practices for the management of patients with immune thrombocytopenia (ITP). This article is an update of the International Consensus Report published in 2010. A critical review was performed to identify all relevant articles published between 2009 and 2018. An expert panel screened, reviewed, and graded the studies and formulated the updated consensus recommendations based on the new data. The final document provides consensus recommendations on the diagnosis and management of ITP in adults, during pregnancy, and in children, as well as quality-of-life considerations.

ABSTRACT: In a previous publication on new terminology, definitions, and outcome criteria for immune thrombocytopenia (ITP), the International Working Group (IWG) on ITP acknowledged that response to treatment should consist of clinically meaningful end points such as bleeding manifestations and that platelet count may not be the ideal parameter for capturing the benefits of therapy. The IWG now proposes a consensus-based ITP-specific bleeding assessment tool (ITP-BAT) with definitions and terminology consistent with those adopted for other bleeding disorders. Bleeding manifestations were grouped into three major domains: skin (S), visible mucosae (M), and organs (O), with gradation of severity (SMOG). Each bleeding manifestation is assessed at the time of examination. Severity is graded from 0 to 3 or 4, with grade 5 for any fatal bleeding. Bleeding reported by the patient without medical documentation is graded 1. Within each domain, the same grade is assigned to bleeding manifestations of similar clinical impact. The “worst bleeding manifestation since the last visit” (observation period) is graded (a suitable database collection form is provided), and the highest grade within each domain is recorded. The SMOG system provides a consistent description of the bleeding phenotype in ITP, and the IWG unanimously supports its adoption and validation in future clinical studies.

Medical therapies for the treatment of immune thrombocytopenia (ITP) complicating SLE are increasingly being investigated as alternatives to splenectomy and IVIG. The purpose of this review is to highlight the therapies that are utilized in the treatment of primary ITP and ITP secondary to lupus.

Recent findings 

Corticosteroids are still the standard initial treatment of ITP, with the addition of IVIG when a rapid response is needed. There are few studies dedicated to assessing the efficacy of disease-modifying antirheumatic (DMARD), biologic, and nonimmunosuppressive agents as treatment for lupus thrombocytopenia/lupus ITP. Rituximab and thrombopoeitin mimetics have been the most extensively studied therapies for primary ITP in recent years. Results of trials show adequate initial responses; however, the duration of therapy and sustainability of responses are variable. Splenectomy is less often utilized.

Summary 

Although corticosteroids, intravenous immunoglobulin and splenectomy have proven to be effective measures to treat immune thrombocytopenia, newer studies have demonstrated positive outcomes of immunosuppressives and thrombopoeitin mimetics. In most cases, the reported duration of therapy was not prolonged. More studies are needed to fully assess the effect of medical therapy in lupus ITP and to determine how long to continue maintenance therapy.

Immune thrombocytopenia is an autoimmune condition characterized by an isolated thrombocytopenia. Despite the low platelet levels, severe bleeding episodes are relatively rare suggesting that patients with ITP may have a protective factor against bleeding. Platelet microparticles (PMP) are thought to play a role in clot formation and some studies have demonstrated higher levels of circulating PMP in patients with ITP. This article provides a review of the epidemiology, mechanism, clinical presentation, management, and prognosis of ITP as well as a review of the literature and discussion regarding PMP and bleeding risk in ITP patients.

ABSTRACT: Immune thrombocytopenia (ITP) is an autoimmune disease defined by low platelet counts which presents with an increased bleeding risk. Several genetic risk factors (e.g., polymorphisms in immunity-related genes) predispose to ITP. Autoantibodies and cytotoxic CD8⁺ T cells (Tc) mediate the anti-platelet response leading to thrombocytopenia. Both effector arms enhance platelet clearance through phagocytosis by splenic macrophages or dendritic cells and by induction of apoptosis. Meanwhile, platelet production is inhibited by CD8⁺ Tc targeting megakaryocytes in the bone marrow. CD4⁺ T helper cells are important for B cell differentiation into autoantibody secreting plasma cells. Regulatory Tc are essential to secure immune tolerance, and reduced levels have been implicated in the development of ITP. Both Fcγ-receptor-dependent and -independent pathways are involved in the etiology of ITP. In this review, we present a simplified model for the pathogenesis of ITP, in which exposure of platelet surface antigens and a loss of tolerance are required for development of chronic anti-platelet responses. We also suggest that infections may comprise an important trigger for the development of auto-immunity against platelets in ITP. Post-translational modification of autoantigens has been firmly implicated in the development of autoimmune disorders like rheumatoid arthritis and type 1 diabetes. Based on these findings, we propose that post-translational modifications of platelet antigens may also contribute to the pathogenesis of ITP.