Platelets play a major role in hemostasis as ppwell as in many other physiological and pathological processes. Accordingly, production of about 10¹¹ platelet per day as well as appropriate survival and functions are life essential events. Inherited platelet disorders (IPDs), affecting either platelet count or platelet functions, comprise a heterogenous group of about sixty rare diseases caused by molecular anomalies in many culprit genes. Their clinical relevance is highly variable according to the specific disease and even within the same type, ranging from almost negligible to life-threatening. Mucocutaneous bleeding diathesis (epistaxis, gum bleeding, purpura, menorrhagia), but also multisystemic disorders and/or malignancy comprise the clinical spectrum of IPDs. The early and accurate diagnosis of IPDs and a close patient medical follow-up is of great importance. A genotype–phenotype relationship in many IPDs makes a molecular diagnosis especially relevant to proper clinical management. Genetic diagnosis of IPDs has been greatly facilitated by the introduction of high throughput sequencing (HTS) techniques into mainstream investigation practice in these diseases. However, there are still unsolved ethical concerns on general genetic investigations. Patients should be informed and comprehend the potential implications of their genetic analysis. Unlike the progress in diagnosis, there have been no major advances in the clinical management of IPDs. Educational and preventive measures, few hemostatic drugs, platelet transfusions, thrombopoietin receptor agonists, and in life-threatening IPDs, allogeneic hematopoietic stem cell transplantation are therapeutic possibilities. Gene therapy may be a future option. Regular follow-up by a specialized hematology service with multidisciplinary support especially for syndromic IPDs is mandatory.

Allogeneic hematopoietic stem cell transplantation recipients have an increasing risk of both hemorrhagic and thrombotic complications. However, the competing risks of two of these life-threatening complications in these complex patients have still not been well defined. We retrospectively analyzed data from 431 allogeneic transplantation recipients to identify the incidence, risk factors and mortality due to thrombosis and bleeding. Significant clinical bleeding was more frequent than symptomatic thrombosis. The cumulative incidence of a bleeding episode was 30.2% at 14 years. The cumulative incidence of a venous or arterial thrombosis at 14 years was 11.8% and 4.1%, respectively. The analysis of competing factors for venous thrombosis revealed extensive chronic graft-versus-host disease to be the only independent prognostic risk factor. By contrast, six factors were associated with an increased risk of bleeding; advanced disease, ablative conditioning regimen, umbilical cord blood transplantation, anticoagulation, acute III-IV graft-versus-host disease, and transplant-associated microangiopathy. The development of thrombosis did not significantly affect overall survival (P=0.856). However, significant clinical bleeding was associated with inferior survival (P<0.001). In allogeneic hematopoietic stem cell transplantation, significant clinical bleeding is more common than thrombotic complications and affects survival.

Primary immune thrombocytopenia (ITP) is a bleeding disorder that conventionally has been treated with steroids or other immunosuppressive treatments. The introduction of thrombopoietin receptor agonists (TPO-RAs), which increase platelet production, dramatically changed the treatment landscape for ITP by providing patients with well-tolerated, long-term treatment options. Two TPO-RAs, eltrombopag and romiplostim, have been approved in the United States and European Union for the treatment of ITP. Some patients do not benefit from the first TPO-RA they receive, so it is assumed that the alternate TPO-RA would have the same outcome. However, eltrombopag and romiplostim have distinct pharmacodynamic and pharmacokinetic properties and may have different tolerability and efficacy in individual patients with ITP. Published retrospective studies showed that >75% of patients who switched to the alternate TPO-RA maintained or achieved a response with the new treatment. Notably, most patients who switched due to lack of efficacy with the first TPO-RA responded to the alternate TPO-RA, which demonstrates an absence of cross-resistance between the two drugs. Therefore, switching to the alternate TPO-RA if the first TPO-RA fails to demonstrate a response should be considered before the use of a less-preferable option.

Immune thrombocytopenia (ITP) is an autoimmune disorder that induces a decrease in the number of circulating platelets due to spleen destruction and inability of megakaryocytes to restore normal counts. Immunosuppressive therapy with glucocorticoid drugs constitutes the first line of treatment. However, lack of response to these agents is not uncommon, and the management of refractory patients is a matter of controversy. In fact, day-to-day clinical practice shows that, in spite of the current guidelines, splenectomy, which is currently considered a suitable second-choice therapy, is being replaced by treatment with thrombopoietin receptor agonists. These boost platelet production by megakaryocytes. The use of one of these, namely eltrombopag, has been permitted for ITP patients refractory to first-line drugs or splenectomy, for the last 10 years. This review summarizes the experience reported using eltrombopag in ITP, paying attention to efficacy and safety. Results from clinical trials will be discussed, and studies performed in the course of daily clinical practice will also be reviewed, as these are useful to assess the potential of the drug in real-world settings. The management of adverse events and the use of eltrombopag in particular situations will also be covered. The experience reported so far permits us to suggest that eltrombopag efficiently induces recovery of platelet counts. Furthermore, recent papers have demonstrated that a sustained response after discontinuation, initially thought to be problematic, may be possible in a nonnegligible number of cases. The safety profile is satisfactory, although patients presenting with thromboembolism risk factors should be treated with caution until the eltrombopag-associated prothrombotic risk is fully established. In summary, although larger studies are still needed to clarify some issues, eltrombopag may be a useful alternative tool for ITP patients refractory to conventional medical management or splenectomy.