Summary Multifactorial mechanisms leading to diminished platelet counts in immune thrombocytopaenia (ITP) might condition the ability of patients with ITP to respond to treatments. Examining their platelet and immune features, we aimed to detect singular characteristics of patients with ITP who do not respond to any treatment. We studied patients with chronic primary ITP who had been without treatment, or untreated (UT‐ITP), for at least six months; included were responders to agonists of thrombopoietin receptors (TPO‐RA), patients who showed no response to first‐ and second‐line treatments (NR‐ITP), and healthy controls. Platelets from NR‐ITP patients exposed a reduced amount of sialic acid residues. Increased loss of platelet surface sialic acid residues was associated with increased platelet apoptosis. NR‐ITP patients had an increased fraction of naive lymphocyte (L) B cells and a reduced LTreg (Lymphocyte T‐regulator) subset. They also presented an anomalous monocyte and NK (Natural Killer) cells distribution. TPO‐RA‐treated patients seemed to recover an immune homeostasis similar to healthy controls. In conclusion, our results indicate a severe deregulation of the immune system of NR‐ITP. The inverse correlation between loss of sialic acid and LTreg count suggests a potential relationship between glycan composition on the platelet surface and immune response, positing terminal sugar moieties of the glycan chains as aetiopathogenic agents in ITP.

Introduction: We present the first registry of patients with congenital bleeding disorders and COVID-19. The study has been carried out in the Community of Madrid, which has the highest number of cases in Spain. The objective is to understand the incidence of COVID-19, the course of the disease if it occurs and the psychosocial and occupational impact on this population. Methods: We included 345 patients (246 of haemophilia, 69 of von Willebrand Disease, two rare bleeding disorders and 28 carriers of haemophilia). A telephone survey was used to collect the data. Results: Forty-two patients presented symptoms suggestive of infection by COVID-19, and in six cases, the disease was confirmed by RT-PCR. The cumulative incidence of our series was 1.73%. It is worth noting the complexity of the management of COVID-19 in two patients on prophylaxis with non-factor replacement therapy. Adherence to

Summary Thrombocytopenia has been identified as a common complication of severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) infection in the general population. In an attempt to determine the impact of coronavirus disease 2019 (COVID‐19) in patients with immune thrombocytopenia (ITP), a retrospective single‐centre study was performed. Thrombocytosis was observed in patients with chronic ITP after SARS‐CoV‐2 infection, frequently needing treatment adjustment or even discontinuation of therapy. Relapses and newly diagnosed cases showed a fast response after initial treatment compared to ITP. Reduced immune activity due to lymphopenia during COVID‐19 could explain this paradoxical effect, although further studies are needed.

The treatment goal for patients with immune thrombocytopaenia (ITP) is to raise platelet counts to levels that minimize or stop bleeding. Thrombopoietin receptor agonists (TPO-RAs) have been successfully and extensively employed as second-line therapy for ITP. However, TPO-RAs have a small but significant increase in the risk of thrombosis. The aim of this study was to elucidate the mechanisms involved in the pro-coagulant effect of TPO-RAs to take them into account when considering their use in ITP patients with concomitant diseases/conditions that might increase risk of suffering thrombotic events. Eighty-two patients with chronic primary ITP (40 untreated and 42 undergoing TPO-RA therapy) and 112 healthy individuals were recruited. The patients with ITP undergoing TPO-RA therapy presented a pro-coagulant profile due to the formation of a more fibrinolysis-resistant clot because of increased plasminogen activator inhibitor-1 (PAI-1) levels. Increase in platelet content of PAI-1 might be the result of the effect of TPO-RA during megakaryopoiesis, as suggested by experiments performed in MEG-01 cells. Moreover, patients under TPO-RA treatment presented an enhanced pro-coagulant activity associated with microparticles and an increased platelet apoptosis that causes a higher exposure of phosphatidylserine and, consequently, a larger surface for the binding of the prothrombinase complex.

Thrombopoietin receptor agonists (TPO-RA) have recently been introduced for the treatment of immune thrombocytopenia (ITP), an anti-platelet-antibodies autoimmune disease. The observation of a low frequency of bleeding episodes despite their thrombocytopenia suggests the existence of a compensatory mechanism. This study aimed to evaluate the effect of TPO-RA treatment on platelet function and on the procoagulant state in ITP patients before (ITP-bR) and after responding (ITP-aR) to treatment. Plasma- and microparticle (MP)-associated procoagulant capacity from ITP patients was similar before and after responding to the TPO-RA regimen but higher than the healthy control values. High MP-associated procoagulant activity did not seem to be due to increased platelet activation, since platelet stimulation by agonists was reduced in ITP-bR and ITP-aR patients. It could be related to increased platelet apoptosis, evaluated in terms of surface phosphatidylserine (PS), observed in both ITP groups. In summary, TPO-RA treatment increased platelet count but did not ameliorate their function and did not change plasma- and MP-associated procoagulant state of ITP patient responders to this therapy.