Mechanisms in childhood idiopathic thrombocytopenic purpura (ITP)

The concepts of the pathological mechanisms in childhood idiopathic thrombocytopenic purpura (ITP) have, to a great extent, been based on clinical experience and on data generated in adults. Studies performed in children have demonstrated that platelet antigen-specific autoantibodies are present in chronic ITP and, to a lesser extent, in acute ITP. It is, however, likely that the mechanisms initiating the production of autoantibodies are different in the two entities. In acute ITP, production of autoantibodies and immune complexes is probably linked to a transient antiviral immune response. Chronic ITP in children is an autoimmune process which eventually is reversible in many cases. The initiating factors, as in other autoimmune disorders, are yet to be elucidated.     

Intravenous immunoglobulin for idiopathic thrombocytopenic purpura (ITP) in childhood

IgG-SRK (identical with Sandoglobulin) is a polyvalent IgG concentrate obtained by modified alcohol cryoprecipitation, including mild acidification at pH 4. This product was given in high doses intravenously for the treatment of six children with acute ITP, four children with intermittent ITP, and three children with severe chronic idiopathic thrombocytopenic purpura (ITP). An impressive initial response was observed in all patients, the extent of which may be of prognostic significance in acute ITP. Maintenance therapy was required in two of six patients with acute ITP, in three out of four patients with intermittent ITP, and in all of the patients with severe chronic ITP. In the cases of severe chronic ITP, the disease could not be adequately controlled over long periods of time, but bleeding episodes subsided or became considerably less frequent. Although little is known of the effects of IgG-SRK, possible mechanisms were discussed. It is emphasized that a new model has been discovered to study the interrelations between structure and function of human immunoglobulin molecules.     

Cytokines in idiopathic thrombocytopenic purpura (ITP)

Most research in idiopathic thrombocytopenic purpura (ITP) has focused on characterization of the autoantibodies directed against platelet antigens resulting in enhanced platelet elimination by macrophages. This report summarizes the current knowledge of cytokine pattern found in individuals with ITP. Serum assessment has demonstrated increased levels of interleukin (IL)-2 and interferon-gamma (IFN-7), while IL-4 was significantly decreased. In addition, thrombopoietin (TPO) has been found in normal levels while IL-11 has been reported to be elevated. These data indicate that ITP is associated with a Th1 type of T helper cytokine response, while that of type Th2 is downregulated. Initially, megakaryocytes are found at normal levels in bone-marrow aspirates, explaining the unchanged production of TPO. The increase in IL-11 may be reflected by the increased number of platelets being produced per megakaryocyte. However, there is little information on these events in immunocompetent sites such as bone marrow, spleen and lymph nodes.     

A cost-utility analysis of treatment for acute childhood idiopathic thrombocytopenic purpura (ITP)

BACKGROUND: The primary objective in the treatment of acute pediatric idiopathic thrombocytopenic purpura (ITP) is to rapidly increase the platelet count. METHODS: We built a decision analytic model to evaluate the cost-utility of four commonly used treatment strategies: intravenous immunoglobulin G (IVIG) 0.8 g/kg, anti-D 75 mcg/kg, methylprednisolone (30 mg/kg for 3 days), and prednisone (4 mg/kg/day for 4 days). In our baseline model, all children were hospitalized upon presentation, and discharged once the platelet count reached > or =20,000. We performed a literature search to estimate time to platelet count > or =20,000 for each strategy, as well as the probability of side effects. We obtained cost data and quality of life measures from institutional and published data sources. RESULTS: Total cost of one-time treatment for a 20 kg child was US dollars 786 with prednisone, US dollars 1,346 with methylprednisolone, US dollars 2,035 with anti-D, and US dollars 2,492 with IVIG. The strategies of IVIG and methylprednisolone were less effective and more expensive than anti-D and prednisone, respectively. Although anti-D caused the most rapid rise in platelet counts, the incremental cost-utility ratio (costs incurred by using anti-D instead of prednisone divided by health benefit of using anti-D instead of prednisone) was US dollars 7,616 per day of severe thrombocytopenia avoided, primarily due to the much higher medication cost of anti-D. Utilizing an outpatient model, the cost difference between anti-D and prednisone was even more striking. CONCLUSIONS: The clinical benefit of anti-D is offset by a substantial cost increase. Although often overlooked in favor of newer agents, a brief course of high-dose prednisone is an inexpensive and effective treatment for acute ITP.     

Intracranial hemorrhage in idiopathic thrombocytopenic purpura (ITP) (author's transl)]

Intracranial hemorrhage is a rare, lifethreatening complication of immun-allergic thrombocytopenia (ITP). A 4 8 1/2 year old boy, who developed intracranial hemorrhage while receiving long term steroid treatment for ITP, was successfully managed by emergency splenectomy. Possible treatment for this condition is discussed.     

Role of the T cell receptor in idiopathic thrombocytopenic purpura (ITP)

During the past few decades a number of studies has described T cell defects and attempted to elucidate their role in the pathogenesis of idiopathic thrombocytopenic purpura (ITP). Some studies implicate T cells as potential initiators of autoantibody production in ITP. However, only a few of these have studied the role that the T cell receptor may play in the pathogenesis of ITP. In a variety of autoimmune syndromes interest has focused on the α- and β-chains of the T cell receptor. Deviations from the normal T cell receptor gene usage have been reported in rheumatoid arthritis, systemic lupus erythaematosus and multiple sclerosis. Usually, these studies have shown a restricted heterogeneity of T cell receptor variable gene usage. The studies on the T cell receptor in ITP have included a limited number of patients, which makes it difficult to evaluate the significance of the role that the T cell receptor may play in the pathogenesis of ITP. Further studies are warranted.     

HLA frequencies and haplotypes in children with idiopathic thrombocytopenic purpura (ITP)

26 patients with an acute reversible ITP and 6 with chronic ITP were tissue typed, together with their healthy first-degree relatives. The HLA frequencies of the different groups were compared with those of a normal control population. The only significant difference between the groups was an increase in the frequency of Aw32 in acute ITP patients. HLA-Aw32 was present in 26.9% of patients, but in only 0.8% of the controls (corrected P=0.000027). The possible importance of associations between antigens of the HLA-A locus with certain diseases are discussed. Family analyses and haplotype determinations proved to be unproductive because no familial clustering of ITP was found.     

Current management issues of childhood and adult immune thrombocytopenic purpura (ITP)

The management of acute and chronic immune thrombocytopenic purpura (ITP) of children differs in many aspects from that of adults. Current paediatric and adult treatment options are discussed in this review in the light of the recently published practice guidelines for the diagnosis and treatment of ITP issued by a panel of paediatric and adult haematologists on behalf of the American Society of Hematology. Uncontrolled rather than controlled randomized studies often represent the basis for treatment decisions. Important issues in improving the management of patients with ITP include the identification of research priorities resulting in controlled clinical trials with well-defined study endpoints, the logistics and coordination of research activities and their presentation at international meetings.     

Directions for research in autoimmune thrombocytopenic purpura (ITP)

All attendees participated in a round-table discussion regarding directions for research in autoimmune thrombocytopenic purpura (ITP). Suggested areas for study were grouped into five main areas: (i) improved classification of ITP identifying subsets of patients with differing clinical syndromes and response to treatment, and those more likely to have serious bleeding manifestations; identification of patients with reduced thrombopoiesis was emphasized; (ii) studies aimed at elucidating the aetiology and pathophysiology of ITP, with emphasis on distinctions between acute and chronic ITP and between patients responsive or refractory to therapy; these studies focused on measures of humoral and cellular immune dysregulation; (iii) studies of platelet function in ITP, with the intent of defining these abnormalities and correlating them with the clinical manifestations of the disease; (iv) new approaches to treatment, particularly of refractory patients; and (v) a miscellaneous group, which included development of an ITP registry, evaluation of the "burden" of disease, investigation of mood changes in ITP, etc. The discussion was not intended to be all-inclusive, but focused on the content of other talks in this symposium. It is hoped that some of thesesuggestions will be further developed for investigation in multicentre co-operative studies to improve the diagnosis, understanding and treatment of ITP.     

Antiplatelet antibodies in childhood idiopathic thrombocytopenic purpura

The serotonin release test using platelets from a panel of donors and autologous platelets after recovery was used to detect platelet antibodies in 42 children with idiopathic thrombocytopenic purpura. The test was done with sera obtained in the thrombocytopenic phase, in partial recovery, and after recovery. The test results for sera from 23 (55%) of 42 patients with thrombocytopenia were positive against platelets from the donors; 14 (61%) of 23 were positive against autologous platelets; and 28 (88%) of 32 were positive against either donor or autologous platelets. Complete recovery occurred in 17 (52%) of 33 patients whose sera had positive tests against the donor platelets at the time of diagnosis. Postrecovery sera from all patients had negative tests against donor platelets, and two (12%) had positive tests against autologous platelets. These results indicate that childhood idiopathic thrombocytopenic purpura is an autoimmune disease caused by platelet antibody that usually disappears with recovery from the thrombocytopenia.     

Interferon-alpha therapy in idiopathic thrombocytopenic purpura

BACKGROUND: Acute idiopathic thrombocytopenic purpura (ITP) represents the most frequent hemorrhagic diathesis in childhood. Up to 30% of patients with ITP are regarded as refractory to standard therapy. The rare mortality from acute ITP in childhood is almost exclusively due to intracranial hemorrhage. This complication occurs in less than 1% of ITP patients. This study was designed to evaluate the effect of alpha-interferon (IFN-alpha) in eight patients whom did not respond to conventional therapy. METHOD: In spite of conventional therapies, the patient whose platelet count could not be increased to 50;10(9)/L were accepted as refractory ITP. Eight of these patients whose platelet count lower than 20;10(9)/L were included in the prospective cohort study. Interferon alpha 2b 5 MU/m(2) was administered subcutaneously three times a week, totalling 12 times in a month. According to the platelet count on the 28th day of therapy, we grouped the patients into three categories. After 60 days, the survey was re-evaluated according to the platelet count. RESULTS: The mean age of children was 3.5+/-2.5 (ranged between 3.5 and 9) years. Six of them were boys and two were girls. There was no response in one patient, partial response in one, and good response in six patients on the 28th day of therapy. The maximum rise in platelet count was observed from 7 to 14 days after the initiation of interferon. The median platelet count which was 15+/-5;10(9)/L before therapy, raised to 60+/-12;10(9)/L after therapy. However, on the 60th day of therapy, there were only two patients who had a platelet count over 100;10(9)/L. CONCLUSION: In our study, we did not observe the long-term benefit of IFN-alpha therapy in refractor ITP in childhood. However, in good responding patients, platelet levels were increased in a short time. Alpha-interferon may be alternative therapy for patients whom had a platelet count below 20;10(9)/L and not responding to standard therapy, or for patients whom immunosuppressive therapy is contraindicated.