Novel approaches to refractory immune thrombocytopenic purpura

Fcγ receptor gene polymorphisms in childhood immune thrombocytopenic purpura

Immune thrombocytopenic purpura (ITP) is a common hematological disorder in the childhood, and it is one of the most common forms of autoimmune disease in pediatric patients. The ITP basis is a primary dysfunction of the immune system. This study aimed to analyze the genetic polymorphisms of the Fcγ receptors IIA and IIIA. The genetic polymorphisms of the Fc receptors γIIA (131H/R) and γRIIIA (158V/F) were analyzed by polymerase chain reaction-restriction fragment length polymorphism technique. Odds ratio and 95% confidence interval were calculated by χ(2) test. Homozygous polymorphic genotype for the FcγRIIIA was significantly more frequent among patients compared with controls (odds ratio = 0.27; 95% confidence interval, 0.09-0.80; P = 0.03). There was no statistical difference between the ITP group and the controls in the analysis of combinations of alleles of the high-affinity Fc receptor, but the ITP individuals with this combination had a lower duration of disease (P = 0.01). Genetic polymorphisms in immune system genes can be important for ITP pathogenesis and disease outcome.

New-generation drugs that stimulate platelet production in chronic immune thrombocytopenic purpura

Idiopathic thrombocytopenic purpura is an acquired disease characterised by a low platelet count. Development of autoantibodies is a main cause of the disease. Although many patients have few symptoms, life-threatening bleeding can arise and hence, when platelet counts fall to unacceptable values treatment should be initiated. However, conventional immunosuppressive approaches can fail, perhaps because of the heterogeneous nature of the disease. Newly developed agents that increase platelet production by stimulating megakaryocytes-such as drugs that bind to the thrombopoietin receptor c-MPL-offer an alternative treatment strategy. Although initial thrombopoietin analogues caused adverse immune reactions, second-generation thrombopoietin-receptor agonists that are in late-stage clinical development seem promising. In particular, eltrombopag and romiplostim safely increase and maintain platelet production in patients with refractory disease. However, long-term side-effects are being assessed and the exact role of these agents in the overall treatment strategy of chronic idiopathic thrombocytopenic purpura remains to be established.

Rituximab treatment for chronic refractory idiopathic thrombocytopenic purpura

Idiopathic thrombocytopenic purpura (ITP) is characterized by mucocutaneous bleeding and a low platelet count caused by increased autoantibodies against self-antigens and T-cell mediated cytotoxicity. About 10-30% patients with ITP will become refractory ITP. Most of them will become refractory to corticosteroids and splenectomy, as well as other available agents such as intravenous immunoglobulins, danazol, or chemotherapy. B cells not only are the passive producers of immunoglobulins, but also play an important immunoregulatory role in pathophysiology of ITP. Rituximab, a chimeric anti-CD20 monoclonal antibody that specifically targets the CD20 molecule on the B-cell surface, is useful in the treatment of ITP through B cells depletion. Rituximab has multiple mechanisms of inducing cytotoxicity in vivo, including antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), direct apoptosis signaling, and possible vaccine effects. In most clinical reports, rituximab was given as an intravenous infusion at a dose of 375 mg/m(2) weekly for four doses. A total complete response (CR) of 33.2% and a total response of 52.9% were reported. Most results found that no clinical or laboratory parameters could predict treatment outcome. Though the infusion-related side effects of rituximab were common in ITP, it was well tolerated with rare severe side effects. In general, rituximab appears to be a promising immunotherapeutic agent for the treatment of refractory ITP. More controlled clinical trials are necessary to evaluate both the efficacy and long-term safety of the drug.

Health-related quality of life measured by the Short Form 36 in immune thrombocytopenic purpura: a cross-sectional survey in China

OBJECTIVES

The aim of this study is to assess the quality of life (QoL) of Chinese adults with idiopathic thrombocytopenic purpura (ITP).

METHODS

The Chinese (mainland) version of Medical Outcome Study SF-36 form (SF-36) Health Survey was used to measure health-related QoL of 236 adults with ITP in a cross-sectional study.

RESULTS

Comparison of SF-36 subscores of patients with ITP with healthy individuals revealed the reduction of QoL in all of the eight SF-36 dimensions. The difference on statistical significance presented in six of eight dimensions of SF-36 including physical functioning (PF), role limitations due to physical problems, body pain, general health perception (GH), social functioning (SF), and role limitations due to emotional problems (RE) between the patients with ITP and the normal population (P < 0.01). The acute ITP group showed better scores in three dimensions including GH, energy/vitality, and RE than chronic ITP (P < 0.01). Meanwhile through classification with platelet count, three subgroups of patients also experienced significant differences in PF, GH, and SF from the eight dimensions. Age was a significant negative predictor of all eight dimensions other than the SF while current platelet count was a significant negative predictor of GH. Moreover, the treatment cost and family income also influenced the QoL scores. The subjective feeling of fear about bleeding had a detrimental impact on QoL.

CONCLUSIONS

QoL was impaired in patients with ITP, especially in the acute patients. The platelet count and the feeling of fear about bleeding had a detrimental impact on QoL.

Critical issues of current and future developments in the treatment of immune thrombocytopenic purpura

B-cell depletion with rituximab has become a reasonable option for thrombocytopenic purpura (ITP) patients who are refractory for corticosteroids and/or splenectomy, with a response rate of about 55%. The side effects are mostly mild and easily manageable. Long lasting responses are likely in patients who achieve normal platelet counts. The mechanism of action of rituximab in immune-mediated disease in general and ITP in particular is not completely clear. Most probably, depletion of the memory B-cell compartment causes a decrease in autoantibody formation. To date it is impossible to predict the response to rituximab, although the presence of a high affinity Fc receptor for IgG seems to have positive predictive value. Future studies will have to clarify these issues, as well as possible effects of repeated rituximab treatment on primary and secondary immune responses.

Treatment of immune thrombocytopenic purpura in children : current concepts

Treatment of immune thrombocytopenic purpura (ITP), the most common bleeding disorder of childhood, is a controversial subject for most practitioners. Diagnosis and management of ITP has historically been based primarily on expert opinion rather than on evidence. Due to a paucity of carefully conducted clinical trials in children, the management of ITP varies widely, ranging from observation only, to aggressive management with intravenous immunoglobulin (IVIG), intravenous anti-D rhesus (Rh)0 immunoglobulin (IV RhIG), corticosteroids, and splenectomy. To address the controversies, the American Society of Hematology (ASH) and the British Society for Hematology (BSH) have developed ITP practice guidelines. These guidelines, based on expert opinion, differ in their recommendations for treatment. The ASH guidelines favor therapy based on a low platelet count, and the more current BSH guidelines recommend a more conservative 'wait and watch' approach. In addition to treating children with severe bleeding symptoms, there is a tendency (not evidence based) to treat early in order to prevent a life-threatening bleeding episode, including intracerebral hemorrhage. Corticosteroids are a highly effective therapy, inexpensive, and can usually increase the platelet count within hours to days. However, chronic or prolonged use is associated with toxicity. In the US, based on the knowledge of known toxicities of corticosteroids, as well as the efficacy of alternative treatments (IV RhIG, IVIG), many pediatricians prefer to treat with IVIG and IV RhIG, reserving corticosteroid treatment for serious bleeding or refractory disease. However, in the UK, for the most part, corticosteroids are used as first-line therapy in children with ITP. Splenectomy is rarely indicated in children except for those with life-threatening bleeding and chronic, severe ITP with impairment of quality of life. For children who develop chronic or refractory ITP, immunosuppressive drugs and/or chemotherapy agents may offer some promise. However, the long-term effects of these drugs in children are unknown and they should not be considered unless there is unequivocal evidence that the patient is refractory to IV RhIG, IVIG, and corticosteroids. To date, virtually all of the randomized clinical trials conducted in children with ITP have focused on platelet counts as the sole outcome measure. Only carefully designed, multicenter, randomized clinical trials comparing the effects of different treatment modalities in terms of bleeding, quality of life, adverse effects, and treatment-related costs will be able to address the controversies surrounding childhood ITP treatment and allow management of this condition to be based on scientific data rather than treatment philosophy.

Autoimmune thrombocytopenia

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder in which platelets coated with mainly antibodies against platelet GPIIb/IIIa and GPIb/IX are destroyed in the spleen. Recent evidence suggests that platelets are also destroyed by cytotoxic T cells. The diagnosis is made by exclusion for other causes of thrombocytopenia. As routine blood counts are becoming more available, many mild cases of ITP (platelets >30 x 10(9) L(-1)) are being diagnosed and they usually do not require treatment. In patients with platelet counts persistently <30 x 10(9) L(-1), treatment with corticosteroids, and/or intravenous immunoglobulin (IVIG) or anti-D may be required. The primary goal of treatment is to maintain the platelet count at a safe level with minimal side effects. After 3-6 months, if spontaneous remission has not occurred and if the side effects are significant, splenectomy is recommended. This is the single most effective treatment of ITP. The refractory patients who fails splenectomy and subsequently first- and second-line therapies, is a management dilemma. Therapeutic options are limited, available treatments potentially toxic and the chances of sustained response low. Observation with no active treatment is a reasonable option. With the increased availability of the thrombopoietic agents in the future, there may be a good prospect of keeping the platelet counts of these refractory patients at a safe long-term level with one of these drugs.

Mycophenolate mofetil as a treatment for refractory idiopathic thrombocytopenic purpura

AIM

To determine whether mycophenolate mofetil (MMF) has beneficial effects on refractory idiopathic thrombocytopenic purpura (ITP) and the corresponding cellular mechanism.

METHODS

Twenty refractory ITP patients resistant to corticosteroid and/or splenectomy and chemical therapy were given MMF 1.5-2.0 g/d orally for a 2 to 4-month period. Serum immunoglobulin was detected by rate nephelometry. Platelet-associated antibodies (PAIgG) were assayed by enzyme-linked immunosorbant assay. The immunophenotypic analysis was performed on a flow cytometer and cell apoptosis was detected with transferase mediated dUTP biotin nick end labeling (TUNEL) method.

RESULTS

Sixteen of the 20 (80%) patients had responses to MMF treatment; 9 (45%) achieved a complete response, 4 (20%) achieved a partial response, and 3 (15%) achieved a minor response. The therapeutic effects were found to be better in male patients than female patients. The number of CD3+ peripheral blood cells (PBCs) and CD4+ PBCs increased and the number of CD8+ PBCs decreased. The plasma level of IgG, IgM, IgA and platelet associated IgG (PAIgG) decreased in 86% of the patients. TUNEL assay showed that mycophenolate acid (MPA) 0.1 mmol/L induced apoptosis of peripheral blood mononuclear cells isolated from refractory ITP patients. The apoptosis rate was increased in male patients after treatment with MPA, but was unchanged in female patients.

CONCLUSION

Therapy for a period of 8 to 16 weeks with median-dose of MMF was valuable for the treatment of refractory ITP.

Immune thrombocytopenic purpura – current management practices

The treatment of patients with immune thrombocytopenic purpura (ITP) is changing rapidly, as new agents demonstrate the capability of improving outcomes and decreasing toxicity. Prior to 1981, the only effective treatment options available to increase platelet counts in persons with ITP were corticosteroids and splenectomy. In recent years, intravenous immunoglobulin (IVIg) and intravenous Rh immunoglobulin (IV RhIg) have demonstrated efficacy comparable to that of corticosteroids for increasing platelet counts in ITP. In addition, IVIg and IV RhIg have demonstrated efficacy for maintaining corticosteroid-induced increased platelet counts by periodic infusion, causing a transient impairment of reticuloendothelial clearance function (medical splenectomy). Thus, the time-proven efficacy of corticosteroids for initial treatment of ITP (induction) may now be supplemented with IVIg or IV RhIg infusions for patients requiring ongoing treatment to support a timely and complete steroid taper, while sustaining the increased platelet count (maintenance) with less toxicity. Several investigators have reported that rituximab (anti-CD20) induced sustained remissions with minimal toxicity, in patients with chronic ITP. These reports are promising and, if confirmed, will provide another effective (spleen-sparing) option for managing acute ITP and a long-awaited option for patients who have had a splenectomy and are refractory to conventional agents. Other treatments, including danazol, azathioprine, cyclophosphamide, vinca alkaloids and cyclosporin A, have advocates, but evidence of their efficacy is limited to relatively small and mostly uncontrolled clinical trials. In our opinion, these agents should be reserved for symptomatic thrombocytopenia after refractoriness to corticosteroids, IVIg, IV RhIg, splenectomy and rituximab has been clearly established.

Reduction of human anti-tetanus toxoid antibody in hu-PBL-SCID mice by immunodominant peptides of tetanus toxoid

Immunotherapy of murine autoimmune and allergic diseases by administration of peptides corresponding to the dominant T cell epitope is a reality. However, problems remain in applying this therapy to reduce antibody responses in humans. To overcome these difficulties, a preclinical system was developed to test the effect of immunodominant peptides from a common antigen, tetanus toxoid (TT), on the long-term human anti-TT response. Individuals whose T cells proliferated against dominant TT peptides were identified. Peripheral blood leucocytes (PBL) from these donors were injected intraperitoneally (i.p.) into mice with severe combined immunodeficiency (SCID) that had been depleted of murine natural killer (NK) cells (hu-PBL-SCID mice). Peptides or PBS were injected i.p. before a further injection of PBL and immunization with TT. The concentration of human IgG and anti-TT in murine plasma was followed for 10 weeks. The total IgG was similar in both groups. By contrast, there was a statistically significant reduction in IgG anti-TT from eight weeks onwards. It is considered that the hu-PBL-SCID model system may provide a means by which the efficacy of peptide immunotherapy for reduction of pathological antibodies in humans can be examined.

21. Immunohematologic disorders

Immunohematologic disorders are a broad group of entities in which hematologic diseases, usually cytopenias, are caused by immune reactions. These reactions lead to the development of hemolytic anemia, thrombocytopenia, or neutropenia, either separately or in combination. Common underlying mechanisms include immunodeficiency, systemic autoimmunity, and drug-induced reactions. Transplacental transfer of maternal alloantibodies can lead to fetal and neonatal cytopenias. Other immune reactions include antibodies to clotting factors, which result in both thrombosis and hemorrhage, and hemolytic and nonhemolytic reactions during transfusion of blood products.