Abstract
A population of 26 children of both sexes mean age 8.5 ± 5.8 years with thrombocytopaenic purpura, disease duration at least 7 months (2.5 ± 1.8 years), platelet count 22 000 ± 12 000/mm3 was studied. Patients were divided into three age groups; I: 2–6 years (8 children); II: 7–10 years (10 children); III: 11–16 years (8 patients). Careful history, physical examination, complete blood count with blood smear, platelet autoantibodies, bone marrow aspirate, and response to intravenous immunoglobulins (IV Igs) were evaluated. Statistical analysis was performed by χ2 test. Platelet count, duration of disease, megakaryocytic reduction, need of splenectomy were significantly lower in younger children than older children of III group (P < 0.05). All patients were responsive to IV Ig. No significant differences of presence of platelet autoantibodies, were found among the groups. Relapse after splenectomy was observed in four older patients among whom three had Evans syndrome: complete remission was obtained with rituximab. Disease duration appears to be associated to megakaryocytic alterations and patient age.
Introduction
Immune thrombocytopaenic purpura (ITP), previously defined as idiopathic thrombocytopaenic purpura, represents the most common autoimmune haematological disorder characterized by peripheral platelet destruction. More recently the current knowledge on the pathogenesis of this disorder has highlighted a frequent involvement of bone marrow precursors with interest at the same time of both peripheral and bone marrow cells.Citation1–Citation6
In childhood the incidence of ITP is 3–10 cases/100 subjects <16 years/year, with a higher incidence peak between 2 and 4 years of life. Recovery, most spontaneous, occurs in 80–90% of cases within a couple of months and at most within the first 6 months after diagnosis.Citation7
About 20% of cases present a chronic form of ITP (C ITP) with duration of disease over the 12 months from the onset, despite traditional treatments.Citation7 In 50% of children with C ITP recovery occur within the first 3–4 years after diagnosis. On the contrary, in adulthood, C ITP represents the most frequent form (80%).Citation8
In some rare cases thrombocytopaenia is associated with autoimmune haemolytic anaemia (Evans syndrome).
Treatment options for immune-mediated haematological disorders include not only corticosteroids and/or intravenous immunoglobulins (IV Igs) as first line-therapy, but also other immuno-modulating drugs and, in refractory cases, splenectomy.
The aim of this study is to evaluate retrospectively – in the last 10 years – in a cohort of 26 paediatric patients with C ITP the interaction between pathogenetic mechanisms and severity of the disease for appropriate management.
Methods
In the last 10 years we have followed 26 children mean age 8.9 ± 6.3 years (2–16 years) of both sexes (16 girls and 10 boys) affected by ITP with disease duration 2.5 ± 1.8 years (15 months–5 years) with mean platelet count 22 000 ± 12 200/mm3 (8000–38 000/mm3) unresponsive to given traditional treatments. Patients were divided in three age groups; I: 2–6 years (8 patients); II: 7–10 years (10 patients); and III: 11–16 years (8 patients).
Diagnosis of ITP was made by a careful history, physical examination, and complete blood count with blood smear. In patients with anaemia indirect bilirubin, lactate dehydrogenase, and direct antiglobulin test were evaluated.
Response to initial treatment with IV Ig and detection of antiplatelet autoantibodies supported and confirmed immuno-pathogenesis of thrombocytopaenia. Antinuclear antibody (ANA), Helicobacter pylori detection was also made to exclude secondary ITP. Bone marrow aspirate was performed.
Antecedent or preceding infections as well as immuno-prophylaxis and family history of thrombocytopaenia or other blood diseases were also evaluated. Informed consent was obtained from parents. Principles outlined in the Declaration of Helsinki were followed. Procedures followed were in accordance with the ethical standards.
Statistical analysis was performed by χ2 test. Significant values was set at P ≤ 0.05.
Results
None patient had family history of blood diseases (data not shown). Antecedent vaccinations performed 1–6 weeks before the onset of ITP were detected only in 25% of I group children (data not shown).
Detection of ANA and H. pylori was negative in all patient groups (data not shown).
Younger patients showed at physical examination more frequent skin petechiae, mucosal bleeding, and easy bruising (87.5% in I group) than older patients (40 and 25% in II and III group, respectively) (I vs. III P < 0.05) ().
Table 1. Differences in the clinical course among the three groups of ITP patients
We also observed that younger children belonging to I group (2–6 years) had significant lower platelet count but shorter disease duration than those of III group (11–16 years) (P < 0.05) ().
Retrospective evaluation on our cohort of children with C ITP shows no significant differences on detection of antiplatelet autoantibodies and response to high doses of IV Ig among the three groups ().
Megakaryocytic reduction (<3/smear) was observed particularly in patients belonging to II and III group (60 and 75%, respectively) and in 12.5% of younger patients (P < 0.05) ().
Furthermore, 25% of I group and 80% of II group patients needed splenectomy (P < 0.05), while all patients belonging to III group were splenectomized (I vs. III P < 0.05) ().
Particularly, we observed recovery after splenectomy in all younger patients (I group), while 20 and 25% of ITP children belonging to II and III group, respectively, showed relapse after splenectomy (P < 0.05) (). These last were treated with rituximab using a dose of 375 mg/m2/weekly for 4 weeks, obtaining complete remission. However, three older patients (II and III group) not responsive to splenectomy showed, in course of ITP, haemolytic anaemia diagnosed on the basis of blood smear, haemolytic indices, and positive direct antiglobulin test (Evans syndrome) (data not shown).
Discussion
Our study shows that older patients had longer duration of ITP than younger children and less remission of disease after splenectomy with need, in some cases, of further treatment with rituximab ().
In addition analysis of bone marrow (BM) specimens highlighted a higher percentage of older children with megakaryocytes reduction than younger patients (P < 0.05) ().
Early studies suggested ITP was primarily due to immune-mediated platelet destruction in reticulo-endothelial system by platelet autoantibodies. However, it has been highlighted that an additional pathogenetic factor could be an immuno-mediated decrease of platelet production.Citation1–Citation6
Moreover, platelet autoantibodies were detected in 50% of our ITP children while all patients were responsive to IV Ig (). Data are in agreement with other studies that detected platelet antibodies in 40–80% of ITP patients.Citation9
The absence of detectable antibodies does not rule out a diagnosis of ITP, because many patients without detectable antibodies respond to traditional ITP therapies and, in our cases, to IV Ig.
On the other hand, antiplatelet antibodies may occur in patients affected by other diseases, such as liver alterations, without clinical thrombocytopaenia.Citation6 However, a minority of children have the refractory chronic form of ITP. It has been also noted that older children with C ITP often have higher platelet associated autoantibody level than younger one. That suggests possible different forms of childhood C ITP. Moreover, it has been observed that younger children have more frequently increased likelihood of remission, whereas in older children the course of chronic disease seems similar to that of adults with unusual remission.Citation10
Process of the humoral immune response in the pathogenesis of the disorder is a complex interaction between antigen-presenting cells and T and B cells.
It has been reported that process of macrophage-mediated platelet destruction and further presentation of new platelet proteins to T and B lymphocytes may contribute to epitope spreading observed over time and more refractory disease in patients with longer duration of ITP.Citation11,Citation12
In addition, it has been pointed out that ITP patients may present a defective immune self-tolerance.Citation11,Citation12 Autoreactive cytotoxic T lymphocytes may induce directly platelet destruction and also megakaryocyte injury reducing platelet turnover.Citation13 Previous autologous platelet turnover studies reported in most patients normal or reduced platelet turnover while it would be expected increased turnover to balance peripheral destruction.Citation5,Citation14 More recent studies supporting suppressed platelet production have shown that in 80% of C ITP forms platelet turnover is reduced with frequent evidence of megakaryocyte damage and autoantibody-induced suppression of megakaryocytopoiesis in vitro.Citation4 Antiplatelet autoantibodies could bind to both platelets and megakaryocytes interfering with their proliferation/maturation or causing intramedullary destruction.Citation3
Furthermore it has been shown that, in many cases, whereas megakaryocytes appeared normal in BM specimens at light microscopy, if the same are observed at electron microscopy showed alterations of both number and appearance.Citation15
So it has been suggested that alterations in regulatory T lymphocytes may be correlated to chronic evolution of ITP unresponsive to traditional treatments.Citation11–Citation13
Recently, the evidence of reduced megakaryocytopoiesis has induced some researchers to detect thrombopoietin (TPO) levels in C ITP patients that, in some cases, resulted low for the degree of thrombocytopaenia.Citation16,Citation17
Furthermore, it has been suggested that in the circulation TPO receptors binding to proteins on platelet surface are cleared with the platelets as well as TPO binding on megakaryocytes.Citation16
On these theoretical basis recently some authors have reported their experience in the C ITP course after failure of traditional therapy with TPO receptors agonists, even if this last therapy remains controversial.Citation18
Moreover, in our cohort of older children we also observed that three patients had association with haemolytic anaemia started in the course of ITP (Evans syndrome) and are unresponsive to usual therapy and to splenectomy.
In our unresponsive cases with relapse after splenectomy we have used treatment with rituximab, an anti-CD20 monoclonal antibody that has gained widespread acceptance in the management of B cell malignancies, obtaining complete remission since 5 years. Moreover, the safety of this approach must be better evaluated by studies on larger populations, even if we think, in agreement with other authors that immunosuppresive risks may be lower in ITP patients that in patients with B cell malignancies because ITP patients are not intrinsically immunosuppressed and not receive additional immunosuppressive therapies.Citation6,Citation19,Citation20
Conclusion
Our experience underlines that immuno-mediated platelet destruction associated with megakaryocytic alterations induce in childhood as well as in adulthood longer duration of the disease. However, we conclude that disease duration is related to patient age. Teenagers appear more like adults in their form of disease than younger children.
We think that in childhood the management of refractory C ITP relapsing after splenectomy needs of further and larger cooperative studies to evaluate the safety of various approaches monitoring some severe reported side effects.Citation21,Citation22
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