Pathophysiology, Clinical Manifestations and Diagnosis of Immune Thrombocytopenia: Contextualization from a Historical Perspective

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by an isolated decrease in the platelet count and an increased risk of bleeding. The pathogenesis is complex, affecting multiple components of the immune system and causing both peripheral destruction of platelets and impaired central megakaryopoiesis and platelet production in the bone marrow. Here, we intend to contextualize the current knowledge on the pathophysiology, terminology, epidemiology, clinical manifestations, diagnosis, and prognosis of ITP from a historical perspective and the first references to the never-stopping garnering of knowledge about this entity. We highlight the necessity to better understand ITP in order to be able to provide ITP patients with personalized treatment options, improving disease prognosis and reducing the incidence or frequency of refractoriness.

Gut microbiota alterations in children and their relationship with primary immune thrombocytopenia

Introduction

Gut microbiota reportedly play a critical role in some autoimmune diseases by maintaining immune homeostasis. Only a few studies have examined the correlation between gut microbiota and the onset of primary immune thrombocytopenia (ITP), especially in children. The purpose of this study was to investigate changes in the composition and diversity of the fecal microbiota of children with ITP, as well as the correlation between such microbiota and the onset of ITP.

Methods

Twenty-five children newly diagnosed with ITP and 16 healthy volunteers (controls) were selected for the study. Fresh stool samples were collected to identify changes in the composition and diversity of gut microbiota as well as for potential correlation analysis.

Results

In ITP patients, the phyla that were most frequently encountered were Firmicutes (54.3%), followed by Actinobacteria (19.79%), Bacteriodetes (16.06%), and Proteobacteria (8.75%). The phyla that were predominantly found in the controls were, Firmicutes (45.84%), Actinobacteria (40.15%), Bacteriodetes (3.42%), and Proteobacteria (10.23%). Compared with those of the controls, the proportions of Firmicutes and Bacteriodetes in the gut microbiota of ITP patients were increased while the proportions of Actinobacteria and Proteobacteria were decreased. Furthermore, gut microbiota in ITP patients varied by age group, showed specific changes in diversity, and were correlated with antiplatelet antibodies. IgG levels were significantly positively correlated with Bacteroides (P<0.01).

Conclusions

The gut microbiota of children with ITP are imbalanced, as shown by the increase in Bacteroidetes, which was positively correlated with IgG. Thus gut microbiota may contribute to ITP pathogenesis via IgG.

Clinical Trial Registration

The clinical trial were registered and approved by the Institutional Review Committee of The Affiliated Huaian No.1 People's Hospital of Nanjing Medical University. Ethics number KY-2023-106-01.

Antiplatelet Antibodies Do Not Predict the Response to Intravenous Immunoglobulins during Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is a rare autoimmune disease due to autoantibodies targeting platelet glycoproteins (GP). The mechanism of platelet destruction could differ depending on the specificity of antiplatelet antibodies: anti-GPIIb/IIIa antibodies lead to phagocytosis by splenic macrophages, in a Fcγ receptor (FcγR)-dependent manner while anti-GPIb/IX antibodies induce platelet desialylation leading to their destruction by hepatocytes after binding to the Ashwell–Morell receptor, in a FcγR-independent manner. Considering the FcγR-dependent mechanism of action of intravenous immunoglobulins (IVIg), we assumed that the response to IVIg could be less efficient in the presence of anti-GPIb/IX antibodies. We conducted a multicentric, retrospective study including all adult ITP patients treated with IVIg who had antiplatelet antibodies detected between January 2013 and October 2017. Among the 609 identified, 69 patients were included: 17 had anti-GPIb/IX antibodies and 33 had anti-GPIIb/IIIa antibodies. The response to IVIg was not different between the patients with or without anti-GPIb/IX (88.2% vs. 73.1%). The response to IVIg was better in the case of newly diagnosed ITP (odds ratio (OR) = 5.4 (1.2–24.7)) and in presence of anti-GPIIb/IIIa (OR = 4.82 (1.08–21.5)), while secondary ITP had a poor response (OR = 0.1 (0.02–0.64)). In clinical practice, the determination of antiplatelet antibodies is therefore of little value to predict the response to IVIg.

Diagnostics of thrombocytopenias

Laboratory methods used for the diagnostics of thrombocytopenias are reviewed. Differential diagnosis is usually carried out between immune and hypoproductive forms of thrombocytopenia. Immune thrombocytopenias are caused by appearance in blood of antiplatelet abtibodies and accelerated destruction of platelets sensibilized by those antibodies, and hypoproductive thrombocytopenias - by impaired platelet production in the bone marrow. Main directions of the laboratory diagnostics of thrombocytopenias - analysis of auto- and alloautoantibodies and evaluation of platelet production and turnover in the blood stream. The following methods are used for the investigation of antiplatelet antibodies: 1) measurement of platelet associated immunoglobulins; 2) determination of circulating antibodies reacting with platelets; 3) determination of antibodies using antigen specific methods - by their reactivity with isolated platelet antigens (glycoproteins). Efficacy of platelet production could be assessed by measuring in blood the amount of "young" (reticulated) platelets. One more method for the evaluation of platelet production as well as the rate of platelet turnover - measurement of plasma soluble glycocalicin, glycoprotein Ib fragment shed from the surface of platelets upon their destruction in spleen and liver. In patients with immune thrombocytopenia autoantibodies are evaluated in all cases, the percentage of reticulated platelets is significantly increased and the amount of plasma glycocalicin is within the normal range or increased. In patients with hypoproductive thrombocytopenia autoantibodies are not detected or detected at low level, the percentage of reticulated platelets is within the normal range or slightly increased and the amount of plasma glycocalicin is lowered. Diagnostics of hapten forms of immune thromocytopenias (heparin-induced thrombocytopenia and others) and of alloimmune thrombocytopenias (neonatal alloimmune thrombocytopenia in particular) are considered in the separate sections of this review.

Recognition of the human antibody-mediated platelet destruction in adult ITP patients by C-reactive protein

Immune thrombocytopenia purpura (ITP) is characterized by destruction of circulating platelets and the presence of antiplatelet IgG antibodies, which opsonize platelets for splenic clearance resulting in low levels of circulating platelets, and the disease severity can be predicted neither by antibody isotype nor by titer, indicating that other factors also play a role. Although the main cause of ITP remains unclear, but its relationship with some infection was demonstrated, including viral or bacterial infections. C-reactive protein (CRP), a member of the pentraxin family, is a major acute-phase protein in humans and is a clinical marker of infection. We aimed to investigate the correlation between the levels of CRP and the presence of antiplatelet IgG antibodies in adults with newly diagnosed ITP. CRP levels and platelet counts were measured in the blood samples from a 60 ITP patient (with confirmed anti-GPIIb/IIIa antibodies), 60 infection patients (all without anti-GPIIb/IIIa antibodies) and 60 normal individuals. The bleeding score, recover time of intravenous immune globulin (IVIg) therapy and the number of megakaryocytes in bone marrow were recorded in ITP patients. The platelet count, bleeding score, recover time of intravenous immune globulin (IVIG) therapy and the number of megakaryocytes in bone marrow and CRP concentrations were compared in ITP group using Spearman's correlation coefficient. We examined the influence of intraperioneal CRP administration on antibody-mediated platelet destruction in mice. There were no statistical differences in gender, age and body mass index among the three groups (P>0.05). Though CRP levels are significantly elevated in ITP patients and infection patients (P<0.05), the platelet count was markedly lower only in ITP patients. We found that CRP was inert toward platelets without antiplatelet antibodies in this study. There are a significant correlation between CRP levels and platelet counts, bleeding severity and the number of megakaryocytes in bone marrow aspiration (r=-0.5079, r=0.5498, r=0.4172, P<0.001, respectively). Moreover, a significant correlation was observed between the recovery time of platelet count and CRP levels (r=-0.5569, P<0.001). In mice, platelet count was lower in Anti-CD41 (0.75 μg)+, CRP (200 μg) group as compared with Anti-CD41 (0.75 μg)+, CRP(-) group and Anti-CD41 (0.75 μg)-, CRP (200 μg) group (P<0.05). In summary, this study indicated that CRP levels are significantly elevated in ITP patients all with confirmed anti-GPIIb/IIIa antibodies, which is able to predict the clinical bleeding severity of ITP patients. The slower CRP levels reduction after IVIg treatment predicted slower platelet count recovery in ITP.

Recognition and management of platelet-refractory bleeding in patients with Glanzmann's thrombasthenia and other severe platelet function disorders

Patients with rare qualitative platelet disorders or platelet function disorders (PFDs) may present to the hospital physician with severe bleeding episodes or excessive surgical bleeding. Although standard treatment consists of platelet transfusions, repeated transfusions may result in the development of antiplatelet antibodies (APA) or clinical refractoriness, rendering further platelet therapy ineffective. In such settings, an approved treatment option for patients with Glanzmann’s thrombasthenia (GT), one of the well-known rare PFDs, is recombinant activated coagulation factor VII (rFVIIa). Data regarding the efficacy of rFVIIa in patients with GT and platelet refractoriness are available from a large patient registry, an international survey, and multiple case reports and demonstrate efficacy in patients with and without refractoriness or APA. This article reviews the rFVIIa clinical data in patients with GT and platelet refractoriness and discusses clinical implications relevant to the hospital-based physician. Because uncontrolled bleeding can be life-threatening, hospital physicians should be alert to the signs of platelet refractoriness, be able to recognize continued internal or external bleeding, and know how to adapt treatment regimens for the effective management of bleeding. The management of patients who receive rFVIIa should occur in consultation with a hematologist with experience in PFDs, and patients with suspected platelet refractoriness should be referred to such a hematologist as early as possible. A critical unmet need is the development of a definition of an adequate response to platelet transfusion, which would facilitate early recognition of platelet refractoriness in patients with PFDs who exhibit a normal platelet count.

Prevalence of HIV-related thrombocytopenia among clients at Mbarara Regional Referral Hospital, Mbarara, southwestern Uganda

Aims/objectives

We aimed to determine the prevalence and correlates of thrombocytopenia among people living with human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) and to assess occurrence of antiplatelet antibodies, among thrombocytopenic HIV clients at Mbarara Regional Referral Hospital, southwestern Uganda.

Materials and methods

This was a retrospective review of hematologic results at enrollment to HIV care from 2005 to 2013. The prevalence and correlates of thrombocytopenia were estimated based on the Immune Suppressed Syndrome (ISS) Clinic electronic database. A cross-sectional study determined the occurrence of antiplatelet antibodies, using the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) technique.

Results

We reviewed 15,030 client records. The median age was 35.0 (range 18–78; interquartile range [IQR] 28–42) years, and there were 63.2% (n=9,500) females. The overall prevalence of thrombocytopenia was 17.4% (95% confidence interval [CI]: 16.8%–18.0%). The prevalence of thrombocytopenia was 17.8% (95% CI: 17.1%–18.4%) among antiretroviral therapy (ART)-naïve clients (n=2,675) and was 13.0% (95% CI: 0.3%–21.9%) for clients who were on ART (n=6). The study found a significant association between thrombocytopenia and other cytopenias, CD4 counts, ART, and deteriorating HIV stage (P<0.05). Two of the 40 participants (5.0%) had antiplatelet antibodies.

Conclusion

This study has showed a high prevalence of HIV-related thrombocytopenia. Antiplatelet antibodies were found in 5.0% of HIV-infected thrombocytopenic participants. Our study shows a significant association of thrombocytopenia burden in a high-HIV study population (Southwest Uganda); therefore, there is need to monitor platelet counts and initiate platelet transfusion in our blood banking practices, to avert possible risks of bleeding.

A case of alloimmune thrombocytopenia, hemorrhagic anemia-induced fetal hydrops, maternal mirror syndrome, and human chorionic gonadotropin-induced thyrotoxicosis

Fetal/neonatal alloimmune thrombocytopenia (FNAIT) can be a cause of severe fetal thrombocytopenia, with the common presentation being intracranial hemorrhage in the fetus, usually in the third trimester. A very unusual case of fetal anemia progressed to hydrops. This was further complicated by maternal Mirror syndrome and human chorionic gonadotropin-induced thyrotoxicosis. Without knowledge of etiology, and possibly due to associated cardiac dysfunction, fetal transfusion resulted in fetal demise. Subsequent testing revealed FNAIT as the cause of severe hemorrhagic anemia. In cases with fetal anemia without presence of red blood cell antibodies, FNAIT must be ruled out as a cause prior to performing fetal transfusion. Fetal heart may adapt differently to acute hemorrhagic anemia compared with a more subacute hemolytic anemia.

Platelet IgG antibodies are significantly increased in chronic liver disease

BACKGROUND

The aim of this study was to investigate the presence of IgG antiplatelet (anti-P) IgG antibodies in patients with chronic liver disease (CLD) of diverse but well defined etiology.

METHODS

One-hundred fifty-six consecutive patients with CLD (65 with chronic hepatitis B, 57 with chronic hepatitis C, 23 with alcoholic liver disease and 11 with primary biliary cirrhosis), and 240 healthy blood donors were investigated for the presence of anti-P antibodies.

RESULTS

Anti-P antibodies were present in 36.5% (57/156) of patients with CLD, and 2.9% (7/240) of controls (P=0.0001). In detail, anti-P antibodies were detected in 35.4% (23/65) of patients with chronic hepatitis B, 26.3% (15/57) of patients with chronic hepatitis C, 47.8% (11/23) of patients with alcoholic liver disease and 72.7% (8/11) of those with primary biliary cirrhosis. The study also demonstrated the significantly higher prevalence of anti-P antibodies in patients with cirrhosis (53.0%) than in non cirrhotic patients (26.4%, P=0.0018). The association of anti-P antibodies with thrombocytopenia was inconsistent.

CONCLUSIONS

This study showed a high prevalence of anti-P IgG antibodies in patients with CLD compared to healthy controls.