Anti-platelet antibodies in childhood immune thrombocytopenia: Prevalence and prognostic implications

Variations of Redox Balance in Different Stages of Childhood Immune Thrombocytopenic Purpura

BACKGROUND

 Few previous studies indicated the role of oxidative stress in the pathogenesis of childhood idiopathic thrombocytopenic purpura (ITP), but there are little data regarding changes in redox balance in different forms of the disease, and changes after therapeutic procedures. We aimed to investigate the values of pro-oxidants and antioxidative capacity in various forms of ITP before and after the applying therapy.

MATERIALS AND METHODS

 The research included 102 children, classified into the following groups: (1) newly diagnosed ITP (ndITP), (2) persistent ITP, (3) chronic ITP (chITP), and (4) control groups: (A) healthy control and (B) previously experienced ITP-healthy children who had been suffering from ITP earlier. During the clinical assessment, a blood sample was taken from the patients, from which the value of pro-oxidants (index of lipid peroxidation measured as TBARS, nitrites [NO2 -], as measurement of nitric oxide [NO] production, superoxide anion radical [O2 -], and hydrogen peroxide [H2O2]) and the capacity of antioxidant protection (activity of superoxide dismutase and catalase, and quantity of reduced glutathione) were determined spectrophotometrically.

RESULTS

 Our results demonstrated that values of pro-oxidants, especially reflected through the TBARS and O2 -, were the highest in the ndITP and exacerbated chITP groups. Also, the activity of the endogenous antioxidative defense system was the lowest in these groups. Intravenous immunoglobulin therapy in the ndITP group exerted the most prominent effect on the redox balance.

CONCLUSION

 It can be concluded that severity and exacerbation of the ITP are closely related to the redox status.

Pathogenesis of refractory ITP: Overview

A subset of individuals with 'primary' or 'idiopathic' immune thrombocytopenia (ITP) who fail to respond to conventional first- and second-line agents or who lose responsiveness are considered to have 'refractory' disease (rITP), placing them at increased risk of bleeding and complications of intensive treatment. However, the criteria used to define the refractory state vary among studies, which complicates research and clinical investigation. Moreover, it is unclear whether rITP is simply 'more severe' ITP, or if there are specific pathogenic pathways that are more likely to result in refractory disease, and whether the presence or development of rITP can be established or anticipated based on these differences. This paper reviews potential biological features that may be associated with rITP, including genetic and epigenetic risk factors, dysregulation of T cells and cytokine networks, antibody affinity and specificity, activation of complement, impaired platelet production and alterations in platelet viability and clearance. These findings indicate the need for longitudinal studies using novel clinically available methodologies to identify and monitor pathogenic T cells, platelet antibodies and other clues to the development of refractory disease.

Re-evaluate the Prognostic Value of Absolute Lymphocyte Count in Pediatric Immune Thrombocytopenia

To re-evaluate the prognostic value of absolute lymphocyte count (ALC) in pediatric immune thrombocytopenia (ITP) from the perspective of age. A total of 242 ITP pediatric patients, including 141 newly diagnosed ITP (nITP), 89 chronic ITP (cITP), and 12 persistent ITP, were retrospectively reviewed for this study. These patients were divided into 3 groups according to age (group 1, ≤24 m; group 2, 24-72 m; and group 3, >72 m). The ALC detected at admission was significantly different between nITP and cITP patients without considering their age difference (5.22 vs. 3.55×10 9 /L, P <0.001). However, no significant difference was discovered after age stratification (≤24 m: 6.52 vs. 5.34×10 9 /L, P =0.161; 24-72 m: 3.78 vs. 3.63×10 9 /L, P =0.748; > 72 m: 2.53 vs. 2.40×10 9 /L, P =0.748). ROC analysis showed that the prognostic value of ALC in ITP children was limited (area under curve (AUC): ≤24 m, 24-72 m, and >72 m were 0.591, 0.570, and 0.542, respectively). Analysis of covariance showed there was no significant difference in ALC between nITP and cITP when considering age as a covariate ( P =0.131). Instead, the ROC showing that platelet to lymphocyte ratio (PLR) has prognostic value in pediatric ITP independent of age stratification (≤24 m: AUC, 0.688; 24-72 m: AUC, 0.741; >72 m: AUC, 0.680). In conclusion, there was no significant difference of ALC between nITP and cITP patients when stratified by different age groups, and PLR may be an optional prognostic indicator for ITP.

Primary immune thrombocytopenia: a 'diagnosis of exclusion'?

Current diagnosis of primary immune thrombocytopenia (ITP) is presumptive, centered on excluding other causes of thrombocytopenia. The diagnosis of ITP is challenging because of the wide range of potential inherited and acquired causes of thrombocytopenia. The treatment of ITP is empiric with steroids, high-dose immunoglobulin, immunosuppressants and thrombopoietin agonists with potential side effects. We searched Medline and Cochrane databases, reviewed the study data and analyzed the individual diagnostic tests for their evidence-based role in the diagnosis of ITP. We then analyzed the strength of the scientific evidence for each diagnostic test in the diagnosis of ITP and identified gaps in the diagnostic accuracy. The diagnostic challenges in ITP include: insufficient evidence for the individual test for diagnosis of ITP, no standardized protocol/guideline for diagnosis, hurdles in accessing the available resources and failure to correlate the clinical data while reviewing the blood smear. We did not identify a diagnostic test that clinicians can use to confirm the diagnosis of ITP. In the absence of a diagnostic test of proven value in ITP, the clinician is best served by a comprehensive history and physical examination, complete blood count and review of the peripheral blood smear in evaluating thrombocytopenia.

Downregulation of ADAM17 in pediatric immune thrombocytopenia impairs proplatelet formation

BACKGROUND

Immune thrombocytopenia (ITP) is the most common etiology of acquired thrombocytopenia diseases in children. ITP is characterized by the immune-mediated decreased formation and excessive destruction of platelets. The pathogenesis and management of pediatric ITP are distinct from adult ITP. A disintegrin and metalloproteinase 17 (ADAM17) mediates the shedding of platelet receptor glycoprotein Ib α (GPIb α) in extracellular domain, functioning in the platelet activation and clearance. Our study aims to probe the roles and mechanisms of ADAM17 in pediatric ITP.

METHODS

The differently expressed ADAM17 in megakaryocytes was obtained from children with ITP through the next-generation RNA-Sequence. Hematoxylin-eosin and Giemsa staining were performed for cell morphology identification. Flow cytometry was applied to assess autoantibodies against platelets, subtypes of lymphocytes, the surface expression level of ADAM17 and polyploidization of megakaryocytes, as well as the full-length GP Ib α.

RESULTS

ADAM17 was significantly downregulated in megakaryocytes and platelets in children with ITP. Higher values of PDW and positive autoantibodies presence were observed in children with ITP. Loss of ADAM17 in mice led to defects in proplatelet formation and significantly elevated expression of phosphorylated myosin light chain (p-MLC) in megakaryocytes.

CONCLUSIONS

Our study indicated that the downregulation of ADAM17 might be an innate cause of inefficient platelet production in pediatric ITP.

An Update on Pediatric Immune Thrombocytopenia (ITP): Differentiating Primary ITP, IPD, and PID

Immune thrombocytopenia (ITP) is the most common acquired thrombocytopenia in children and is caused by both immune-mediated decreased platelet production and increased platelet destruction. In the absence of a diagnostic test, ITP must be differentiated from other thrombocytopenic disorders, including inherited platelet disorders (IPD). In addition, a diagnosis of secondary ITP due to a primary immune deficiency (PID) with immune dysregulation may not be apparent at diagnosis but can alter management and should be considered in an expanding number of clinical scenarios. The diagnostic evaluation of children with thrombocytopenia will vary based on the clinical history and laboratory features. Access to genotyping has broadened the ability to specify the etiology of thrombocytopenia, while increasing access to immunophenotyping, functional immunologic and platelet assays, and biochemical markers has allowed for more in-depth evaluation of patients. With this greater availability of testing, diagnostic algorithms in patients with thrombocytopenia have become complex. In this article, we highlight the diagnostic evaluation of thrombocytopenia in children with a focus on ITP, including consideration of underlying genetic and immune disorders, and utilize hypothetical patient cases to describe disease manifestations and strategies for treatment of pediatric ITP.

Biological stratification of clinical disease courses in childhood immune thrombocytopenia

BACKGROUND

In childhood immune thrombocytopenia (ITP), an autoimmune bleeding disorder, there is a need for better prediction of individual disease courses and treatment outcomes.

OBJECTIVE

To predict the response to intravenous immunoglobulins (IVIg) and ITP disease course using genetic and immune markers.

METHODS

Children aged younger than 7 years with newly diagnosed ITP (N = 147) from the Treatment With or Without IVIG for Kids with ITP study were included, which randomized children to an IVIg or observation group. A total of 46 variables were available: clinical characteristics, targeted genotyping, lymphocyte immune phenotyping, and platelet autoantibodies.

RESULTS

In the treatment arm, 48/80 children (60%) showed a complete response (platelets ≥100 × 109 /L) that lasted for at least 1 month (complete sustained response [CSR]) and 32 exhibited no or a temporary response (absence of a sustained response [ASR]). For a biological risk score, five variables were selected by regularized logistic regression that predicted ASR vs CSR: (1) hemoglobin; (2) platelet count; (3) genetic polymorphisms of Fc-receptor (FcγR) IIc; (4) the presence of immunoglobulin G (IgG) anti-platelet antibodies; and (5) preceding vaccination. The ASR sensitivity was 0.91 (95% confidence interval, 0.80-1.00) and specificity was 0.67 (95% confidence interval, 0.53-0.80). In the 67 patients of the observation arm, this biological score was also associated with recovery during 1 year of follow-up. The addition of the biological score to a predefined clinical score further improved the discrimination of favorable ITP disease courses.

CONCLUSIONS

The prediction of disease courses and IVIg treatment responses in ITP is improved by using both clinical and biological stratification.

Diagnostic and Predictive Contribution of Autoantibodies Screening in a Large Series of Patients With Primary Immunodeficiencies

Objectives

To evaluate the diagnostic and predictive contribution of autoantibodies screening in patients with primary immunodeficiencies (PIDs).

Methods

In the present study, PID patients and healthy controls have been screened for 54 different autoantibodies. The results of autoantibodies screening in PID patients were correlated to the presence of autoimmune diseases.

Results

A total of 299 PID patients were included in this study with a predominance of antibody deficiencies (27.8%) followed by immunodeficiencies affecting cellular and humoral immunity (26.1%) and complement deficiencies (22.7%). Autoimmune manifestations were present in 82 (27.4%) patients. Autoimmune cytopenia (10.4%) was the most common autoimmune disease followed by gastrointestinal disorders (10.0%), rheumatologic diseases (3.7%), and endocrine disorders (3.3%). Autoantibodies were found in 32.4% of PID patients and 15.8% of healthy controls (P < 0.0005). Anti-nuclear antibodies (ANA) (10.0%), transglutaminase antibody (TGA) (8.4%), RBC antibodies (6.7%), anti-smooth muscle antibody (ASMA) (5.4%), and ASCA (5.0%) were the most common autoantibodies in our series. Sixty-seven out of the 82 patients with autoimmune manifestations (81.7%) were positive for one or more autoantibodies. Eleven out of the 14 patients (78.6%) with immune thrombocytopenia had positive platelet-bound IgM. The frequencies of ASCA and ANCA among patients with IBD were 47.4% and 21.0% respectively. All patients with celiac disease had TGA-IgA, while six out of the 11 patients with rheumatologic diseases had ANA (54.5%). Almost one third of patients (30/97) with positive autoantibodies had no autoimmune manifestations. ANA, rheumatoid factor, ASMA, anti-phospholipid antibodies and ANCA were often detected while specific AID was absent. Despite the low positive predictive value of TGA-IgA and ASCA for celiac disease and inflammatory bowel disease respectively, screening for these antibodies identified undiagnosed disease in four patients with positive TGA-IgA and two others with positive ASCA.

Conclusion

The present study provides valuable information about the frequency and the diagnostic/predictive value of a large panel of autoantibodies in PIDs. Given the frequent association of some AIDs with certain PIDs, screening for corresponding autoantibodies would be recommended. However, positivity for autoantibodies should be interpreted with caution in patients with PIDs due to their low positive predictive value.

Anti-platelet antibodies in childhood immune thrombocytopenia: Prevalence and prognostic implications

BACKGROUND

Anti-platelet antibody testing may be useful for the diagnosis and management of childhood immune thrombocytopenia (ITP).

OBJECTIVES

Here we aimed to assess the prevalence and prognostic significance of anti-platelet glycoprotein-specific IgM and IgG antibodies.

METHODS

Children with newly diagnosed ITP were included at diagnosis and randomized to an intravenous immunoglobulins (IVIg) or careful observation group (TIKI trial). In this well-defined and longitudinally followed cohort (N = 179), anti-platelet glycoprotein-specific IgM and IgG antibodies were determined by monoclonal antibody-immobilization of platelet antigens.

RESULTS

The dominant circulating anti-platelet antibody class in childhood ITP was IgM (62% of patients); but IgG antibodies were also found (10%). Children without IgM platelet antibodies were older and more often female. There was weak evidence for an association between IgM anti-GP IIb/IIIa antibodies and an increased bleeding severity (P = .03). The IgM and IgG anti-platelet responses partially overlapped, and reactivity was frequently directed against multiple glycoproteins. During 1-year follow-up, children with IgM antibodies in the observation group displayed a faster platelet recovery compared to children without, also after adjustment for age and preceding infections (P = 7.1 × 10-5 ). The small group of patients with detectable IgG anti-platelet antibodies exhibited an almost complete response to IVIg treatment (N = 12; P = .02), suggesting that IVIg was particularly efficacious in these children.

CONCLUSIONS

Testing for circulating anti-platelet antibodies may be helpful for the clinical prognostication and the guidance of treatment decisions in newly diagnosed childhood ITP. Our data suggest that the development of even more sensitive tests may further improve the clinical value of antibody testing.