Different forms of chronic childhood thrombocytopenic purpura defined by antiplatelet autoantibodies

Risk factors and disease trajectories of recurrent immune thrombocytopenia in children

This retrospective study aimed to analyse the course and outcome of recurrent immune thrombocytopenia (ITP) in children and to identify factors associated with recurrence. A total of 497 newly diagnosed ITP children with platelet <30 × 109/L between January 1988 and December 2019 were included. Recurrent ITP was defined as a new event of thrombocytopenia after at least 3 months of remission without treatment. Twenty-nine (5.8%) children experienced 48 recurrent episodes. The median time from diagnosis to recurrence was 22 months. Most recurrences occurred in children aged 1.5-10 years with a recent infection history. Compared to non-recurrent ITP, children with recurrent ITP had delayed remission with lower platelets at 1 month and 3 months postdiagnosis. Multivariate analysis identified aged 1.5-10 years (hazard ratio [HR] 3.65, 95% confidence interval [CI]: 1.35-9.82) and delayed remission at 7-12 months (HR 4.04, 95% CI: 1.37-11.95) as predictors for recurrence. Most recurrent ITP patients had minor or mild symptoms, higher platelet counts, did not require treatment, and achieved remission within 12 months. The similar remission trajectories among the first and recurrent ITP, but different from the courses in the non-recurrent ITP, suggest that recurrent ITP might have a unique biological basis.

Anti-platelet antibody immunoassays in childhood immune thrombocytopenia: a systematic review

BACKGROUND

In adult immune thrombocytopenia (ITP), an acquired autoimmune bleeding disorder, anti-platelet autoantibody testing may be useful as a rule-in test. Childhood ITP has different disease characteristics, and the diagnostic and prognostic value of anti-platelet antibody testing remains uncertain.

OBJECTIVE

To systematically review the diagnostic accuracy of anti-platelet autoantibody testing in childhood ITP.

METHODS

PubMed and EMBASE were searched for studies evaluating immunoassays in childhood ITP. Study quality was assessed (QUADAS2), and evidence was synthesized descriptively.

RESULTS

In total, 40 studies (1606 patients) were identified. Nine studies reported sufficient data to determine diagnostic accuracy measures. Anti-platelet IgG antibody testing showed a moderate sensitivity (0·36-0·80 platelet-associated IgG [direct test]; 0·19-0·39 circulating IgG [indirect test]). In studies that reported control data, including patients with non-immune thrombocytopenia, specificity was very good (0·80-1·00). Glycoprotein-specific immunoassays showed comparable sensitivity (three studies) and predominantly identified IgG anti-GP IIb/IIIa antibodies, with few IgG anti-GP Ib/IX antibodies. Anti-platelet IgM antibodies were identified in a substantial proportion of children (sensitivity 0·62-0·64 for direct and indirect tests).

CONCLUSION

The diagnostic evaluation of IgG and IgM anti-platelet antibodies may be useful as a rule-in test for ITP. In children with insufficient platelets for a direct test, indirect tests may be performed instead. A negative test does not rule out the diagnosis of ITP. Future studies should evaluate the value of anti-platelet antibody tests in thrombocytopenic children with suspected ITP.

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.

Flow cytometric measurement of platelet-associated immunoglobulin in children with newly diagnosed Immune Thrombocytopenia

OBJECTIVE

To explore the clinical utility of measuring platelet-associated immunoglobulin (PAIG) at the time of diagnosis in children with immune thrombocytopenia (ITP).

METHODS

PAIG was measured by flow cytometry using fluorescent murine anti-IgG and anti-IgM. In a cohort of 88 children with ITP, the assay was performed within 15 days of diagnosis and before any treatment in 68 cases. We reviewed the results and examined the relation of isotype profile and degree of elevation to clinical manifestations and course of disease.

RESULTS

PAIG was elevated in 74%, with raised IgM being more frequent than IgG (63% vs. 44%, P = 0.04) and with isotype profile depending on symptom onset. Platelet counts at presentation were similar in all subgroups, but mucosal bleeding was less frequent in PAIG-negative patients compared to the positive groups (5.5% vs. 34%, P = 0.03). Duration of thrombocytopenia was similar in negative and positive cases, but during follow-up, significant bleeding events occurred less frequently in PAIG-negative patients (0% vs. 14%, P = 0.18).

CONCLUSION

Approximately one-quarter of children are PAIG-negative, and these children have milder bleeding tendency at diagnosis and lower morbidity during follow-up. Raised PAIG possibly may cause some degree of platelet dysfunction.

Immune regulation by B cells and antibodies a view towards the clinic

B lymphocytes contribute to immunity in multiple ways, including production of antibodies, presentation of antigen to T cells, organogenesis of secondary lymphoid organs, and secretion of cytokines. Recent clinical trials have shown that depleting B cells can be highly beneficial for patients with autoimmune diseases, implicating B cells and antibodies as key drivers of pathology. However, it should be kept in mind that B cell responses and antibodies also have important regulatory roles in limiting autoimmune pathology. Here, we analyze clinical examples illustrating the potential of antibodies as treatment for immune-mediated disorders and discuss the underlying mechanisms. Furthermore, we examine the regulatory functions of activated B cells, their involvement in the termination of some experimental autoimmune diseases, and their use in cell-based therapy for such pathologies. These suppressive functions of B cells and antibodies do not only open new ways for harnessing autoimmune illnesses, but they also should be taken into account when designing new strategies for vaccination against microbes and tumors.

T-cell-mediated cytotoxicity toward platelets in chronic idiopathic thrombocytopenic purpura

Chronic idiopathic thrombocytopenic purpura (ITP) is a bleeding disorder that is characterized by increased platelet destruction and is believed to be autoantibody mediated. In this study, CD3+ T cells from ITP patients had increased expression of genes involved in cell-mediated cytotoxicity. In addition, cytotoxic cell-mediated lysis of autologous platelets was shown in active ITP. Our data suggest that T-cell-mediated cytotoxicity is an alternative mechanism for platelet destruction in ITP.

Immune thrombocytopenic purpura

Although many advances have been achieved in the understanding of ITP, critical issues regarding the pathophysiology and biology of the disease remain to be elucidated. The recent characterization of the human genome along with new sophisticated molecular biology techniques will allow basic researchers to study genes that may affect the presentation and clinical course of the disease. Different patterns of gene expression in this population can be studied, leading to the identification of subsets of patients with ITP at higher risk of bleeding. The multigene patterns of expression might also provide clues about regulatory mechanisms and broader cellular functions. In order to answer essential clinical questions, like the incidence of ICH in relation to drug treatment or observation alone, clinical trials should be appropriately designed. More studies are necessary to better define the optimal treatment approach for each child with ITP. Even though the incidence of intracranial hemorrhage cannot be used as the primary outcome measure because of its rarity, numerous other outcomes, such as rate of rise in platelet count, cost and side effects of therapy, health related quality of life of the patient and family, and severity of hemorrhage can be measured and compared between treatment groups. Future investigators should find it attractive to conduct trials in children with this common hematological disease so that decision making can be based more on scientific evidence than on anecdote and opinion.

Chronic childhood idiopathic thrombocytopenic purpura

Childhood idiopathic thrombocytopenic purpura (ITP) is a largely trivial disorder from which over 95% of children sooner or later recover spontaneously, and for most of whom the risks of unnecessary or ineffective therapy are arguably greater than those of the untreated disease. There are, however, a few patients who continue to have very low platelet counts and remain symptomatic for many months or years. They are rare, and they present difficult management problems. Splenectomy is probably the most effective treatment but is also the most dangerous and is not always successful. It is also irreversible. Most other regimens are either ineffective, unacceptably toxic, or both. Planning management for an individual patient requires a realistic risk:benefit appraisal, a process that is impeded by inadequate epidemiological data and a scarcity of large-scale randomized clinical trials. International collaborative studies may help in the future.

Virus-associated idiopathic thrombocytopenic purpura

Two-thirds of children with acute idiopathic thrombocytopenic purpura (ITP) have a history of an infectious illness a few days to a few weeks before the onset of thrombocytopenia. In a subset of affected children, identification of a specific virus can be made, such as varicella zoster virus, rubella, Epstein-Barr virus, influenza, or human immunodeficiency type 1 virus, indicating an etiological role for preceding viral infection in these children with ITP. While inhibition of thrombopoiesis has been established to play a role in thrombocytopenia associated with infection with some viruses, it does not appear to play a major role in the etiology of most typical ITP cases. Rather, enhanced clearance of platelets by the reticuloendothelial system is considered to be, at least in part, responsible for the thrombocytopenia which occurs during the viremic phase of acute virus infection or which develops days to weeks following the virus illness. Molecular mimicry between viral antigens and host proteins has been implicated in a number of autoimmune phenomena, and may be involved in the enhanced platelet clearance in virus-associated ITP.

Immune thrombocytopenic purpura ITP

Immune thrombocytopenic purpura ITP is characterized by early platelet destruction due to an imbalanced immune response. In acute ITP, a transient increase of HLA-DR molecules has been detected while in individuals with chronic ITP, in addition, increased serum concentrations of IL-2 and other cytokines reflecting in vivo T-cell activation have been observed. Clinically, the hemorrhagic manifestation of ITP rather than the platelet count should define the indication for active intervention. In a staging system a patient with stage III has bleeding signs and platelet counts below 10 or 20 x 10(9)/L and needs treatment, a patient with stage II should be treated on an individual level (prevention of bleeding) and a patient with stage I (no bleeding, platelet count above 50 x 10(9)/L) should be observed only.

Platelet antibody detection in pediatric immune thrombocytopenic purpura: evaluation of three screening methods

BACKGROUND AND OBJECTIVES

Immune thrombocytopenic purpura (ITP) is a common hematologic disorder, two forms of which occur in children. The detection of circulating platelet antibodies is helpful in diagnosis.

MATERIALS AND METHODS

We evaluated three different immunological methods for detecting platelet antibodies in the serum of children with ITP. These were: a solid-phase red-cell adherence test (SPRCA), an enzyme immunoassay (EIA), and an immunofluorescence test (PSIF).

RESULTS

The sensitivity of the methods in detecting IgG antibodies ranged from 28.1 (EIA) to 39.4% (SPRCA). We also looked for IgM antibodies by PSIF, thus raising the sensitivity of this test from 32.0 to 40.0%. A combination of two tests (SPRCA and EIA) allowed us to detect 61.8% positive samples. By doing all three tests, we obtained 71.3% positive samples. Finally, we reached 73.5% by adding PSIF for IgM. We found a higher frequency of circulating antibodies in both acute and chronic ITP at onset than in clinical remission. There were a few positive sera in chronic ITP, but not in the acute form in remission.

CONCLUSION

The individual tests each have a relatively low sensitivity, but the combination of all three increases the diagnostic effectiveness. The finding of platelet antibodies during remission may predict evolution toward a systemic autoimmune state.

Intra-abdominal bleeding in a 14-year-old girl with acute immune thrombocytopenic purpura

We describe a 14-year-old girl with acute immune thrombocytopenic purpura. She presented with acute abdominal pain, and her hematocrit decreased from 44% to 29%. The bleeding was due to the rupture of a distended follicle on about the 14th day of her menstrual cycle. The patient's low platelet count made possible the continuous oozing of blood from the follicle into the abdominal cavity, causing peritoneal irritation and the fall in hematocrit. She received treatment with intravenous Ig. This case indicates that unnecessary surgery can be avoided if there is reason to believe that the cause of internal bleeding does not require surgical intervention.

Characterization of autoantibodies against the platelet glycoprotein antigens IIb/IIIa in childhood idiopathic thrombocytopenia purpura

The majority of children with idiopathic thrombocytopenia (ITP) have an acute self-limiting course and no diagnostic test has been identified which will predict the course of thrombocytopenia and detect those with the chronic autoimmune form. The detection of autoantibodies directed against the platelet glycoprotein complex IIB/IIIa, may identify patients with chronic ITP. Serum anti-GP IIb/IIIa antibodies were assessed by the indirect MAIPA assay in 54 children with immune thrompocytopenia at initial presentation along with an additional 7 children previously diagnosed with chronic ITP, to determine if there was a difference in antibody positivity between acute and chronic ITP patients, and whether the identification of antibodies could be used as a predictive test at diagnosis. There was no significant difference in the percentage of antibodies detected in children classified with acute ITP (27/40-68%) compared to children with chronic ITP (13/21-62%, P > 0.05). Patients with acute ITP had significantly lower mean platelet counts at diagnosis compared to the chronic ITP group (16,225/mm3 vs 32,250/mm3, P < 0.05), though there was no significant difference in the bleeding manifestations between the acute and chronic ITP groups. Serum anti-GP IIb/IIIa antibodies are detected in a high percentage of children with ITP and autoantibodies appear to be involved in the pathogenesis of both acute and chronic ITP. The detection of anti-GP IIb/IIIa antibodies at diagnosis, however, does not appear to be a useful prognostic test in childhood ITP.

Immunthrombocytopenic purpura as a model for pathogenesis and treatment of autoimmunity

In honour of Professor Rossi's 80th birthday we review the development of our understanding of the immune and auto-immune nature of the pathogenesis of immune thrombocytopenic purpura (ITP). The immune aspects have been documented by postviral alterations of the cellular and humoral immune system, by new methods of specific auto-antibody detection against platelet glycoproteins and by the therapeutic effect of administering immunoglobulin concentrate from healthy blood donors. The various possible mechanisms of action of immunoglobulin treatment have led to use of this treatment as an alternative for other immune-related disorders. The treatment of severe chronic ITP in children, however, remains unsatisfactory. With a new international clinical and laboratory study of children and adolescents with early chronic ITP we are continuing the investigation of the pathogenesis and treatment of ITP.

HLA class-I and -II antigens in chronic idiopathic autoimmune thrombocytopenia

We studied MHC class-I and -II phenotypes in adult Caucasian patients with chronic idiopathic autoimmune thrombocytopenia (cAITP). Forty-five patients (median age 51 years, range 21-78 years) with a median disease duration of 7 years (range 2-26 years) were phenotyped for HLA-A, -B, -C by the standard lymphocytotoxicity test, HLA-DR and -DQ by restriction fragment-length polymorphism (RFLP), and -DP by oligonucleotide typing. Antiplatelet antibodies directed against glycoproteins Ib/IX and IIb/IIIa were determined by monoclonal antibody-specific immobilization of platelet antigens (MAIPA). The comparison of antigen frequencies of the whole group of patients with healthy controls revealed no significant difference for any of the MHC class-I or class-II specificities (p > 0.05). Patients were then divided into groups based on (a) their response to therapy, and (b) on whether they did or did not have detectable anti-platelet antibodies (n = 16 versus n = 29). All patients with a poor response to splenectomy carried the HLA-DPB1*0402 phenotype. The HLA-DPB1*1501 allele was found only among patients with detectable antiplatelet antibodies. These differences were not significant after correction for the number of tested antigens, however. Our data suggest that there is no association between MHC class-I/II alleles and adult cAITP or subgroups thereof.

Coincidence of familial platelet glycoprotein Ib/IX deficiency (Bernard-Soulier syndrome), idiopathic autoantibody against platelet glycoprotein Ib/IX, familial appearance of antiphospholipid antibodies, and familial factor XII deficiency

The case of an 8-year-old boy with apparently homozygous Bernard-Soulier syndrome (platelet GP Ib/IX complex deficiency) and a transient idiopathic autoantibody against GP Ib/IX is described. He had been diagnosed with chronic autoimmune thrombocytopenia (due to the detection of antiplatelet autoantibodies) before Bernard-Soulier syndrome was proven. Both parents and his brother displayed intermediate deficiency of GP Ib/IX, thus indicating a heterozygote state for Bernard-Soulier syndrome. Alloimmunization as an explanation for the appearance of GP Ib/IX antiplatelet antibodies in the propositus can be excluded. A so-called pseudo Bernard-Soulier syndrome due to selective antibodies was also excluded. Flow cytometric analysis revealed residual expression of 2% GP Ib and 13% GP IX on the propositus' platelets. It seems that the propositus showed an idiopathic autoantibody against a platelet glycoprotein in which he is genetically deficient (but which is not completely lacking). Thus, in patients with untypical behavior upon therapy of "autoimmune thrombocytopenia", other differential diagnoses should also be considered even if antiplatelet antibodies are detected. In addition, all family members displayed elevated concentrations of antiphospholipid antibodies. These findings raise the question of a genetic predisposition for the development of autoantibodies. Moreover, an F. XII deficiency was found in all family members except the mother.

Immune thrombocytopenic purpura and intravenous immunoglobulin

The observation, in 1980, of a rapid increase in platelet counts as a result of administration of intravenous immunoglobulin (IVIG) in a patient with immune thrombocytopenic purpura (ITP) was followed by clinical studies confirming the efficacy of this new treatment alternative in ITP. Simultaneously, new sensitive assays using monoclonal antibodies against platelet glycoproteins showed that chronic ITP in adults and children is often an autoimmune disorder. There seem to be both immediate and long-term effects of IVIG in ITP which may be explained by mechanisms of action other than immunoglobulin G substitution. The mode of action of IVIG could correspond to interference with Fc receptors on phagocytes or be a result of antiidiotypic antibodies in IVIG that may induce secondary changes in the complex immunologic network. These immunomodulatory effects were the basis for the use of IVIG in the treatment of patients with other immune-related disorders. New aspects regarding definition and treatment of ITP, the possible mechanisms of action of IVIG, and the implications thereof are discussed and updated.