Efectividad de Rituximab en el tratamiento de citopenias autoinmunes refractarias en adultos / Effectiveness of Rituximab in the treatment of cytopenias refractory autoimmune in adults

The term autoimmune cytopenias is referred to a heterogeneous group of diseases characterized by a reduced peripheral blood cell counts in one or more cellular series, because an immunological disorder. The first line therapy is steroids, followed by splenectomy or immunesupressant therapy in non-responders. Rituximab is an anti CD20 monoclonal antibody used as a third line in refractory patients or as an alternative to splenectomy. We present a retrospective study of nine patients with autoimmune cytopenias treated in a public hospital setting with rituximab. Five patients with the diagnosis of inmune thrombocytopenic purpura received it, all of them achieved hematological response (4 complete and one partial). The median time to the best response was 6 weeks, staying in this category after 6 months of follow up. Four patients with autoimmune hemolytic anemia received rituximab, three of them achieving partial response and one was lost from follow up. No severe adverse effects related to rituximab were registered.

Distinct clinical correlates of immune thrombocytopenic purpura at diagnosis of childhood-onset and adult SLE.

OBJECTIVES: To compare clinical and laboratorial features between childhood-onset systemic lupus erythematosus (cSLE) and adult SLE (aSLE) at concomitant diagnosis of immune thrombocytopenic purpura (ITP). METHODS: This study evaluated 56 cSLE and 73 aSLE patients regularly followed at Pediatric and Rheumatology Divisions of the same University hospital with ITP (platelets count <100,000/mm3 in the absence of other causes) at lupus onset. RESULTS: Median current age was 11.6 and 27.3 years in cSLE and aSLE, respectively. cSLE had a higher frequency of ITP compared to aSLE (17% vs. 4%, p < .0001) and the former group had more hemorrhagic manifestations (36% vs. 16%, p = .0143). Constitutional symptoms and reticuloendothelial manifestations (p < .05), as well as pericarditis (25% vs. 10%, p = .029) and central nervous system (CNS) involvement (30% vs. 14%, p = .029) were more common in cSLE. Conversely, in aSLE, ITP was solely associated with cutaneous and articular involvements (p < .05). Concerning treatment, intravenous methylprednisolone, intravenous immunoglobulin, blood transfusion and platelets transfusion were more frequently used in the cSLE population (p < .05). CONCLUSION: ITP at cSLE has distinct features compared to aSLE with a more severe presentation characterized by concomitant constitutional/reticuloendothelial manifestations, CNS involvement and hemorrhagic manifestation. These findings reinforce the need for a more aggressive treatment in this age group.

Zika virus and autoimmunity. One-step forward.

Zika virus (ZIKV) infection has been associated with the development of Guillain-Barré syndrome (GBS) and idiopathic thrombocytopenic purpura (ITP). Whether ZIKV infection is related to other autoimmune diseases is unknown. Therefore, an association study to evaluate rheumatic and thyroid autoimmunity in patients with ZIKV disease was conducted through a panel of 14 autoantibodies. In addition, a literature review on ZIKV, and GBS and ITP was performed. Our results disclosed a lack of association of rheumatoid and thyroid autoimmunity with ZIKV disease. A total of 272 cases of GBS related to ZIKV were retrieved from the literature, the majority of them being males (54.8%). Electrophysiological findings indicated acute inflammatory demyelinating polyneuropathy as the most frequent subphenotype (75.7%). Up to date, twenty-four cases of ITP in patients with ZIKV disease have been published. Although a few fatal cases have been observed, most of the reported patients responded well to immunomodulatory treatment. A review of the mechanisms incriminated into the development of autoimmune phenomenon in ZIKV disease indicates molecular mimicry as the most plausible one. Nevertheless, more research aimed at deciphering ZIKV disease pathogenesis and its relationship with autoimmunity is warranted.

Circulating myeloid-derived suppressor cells predict disease activity and treatment response in patients with immune thrombocytopenia.

Immune thrombocytopenia (ITP) is a disease characterized by isolated thrombocytopenia. Abnormal effector T cell activation is an important mechanism in the pathogenesis of ITP. Regulatory T cells (Treg) have a strong immunosuppressive function for T cell activation and their importance in the pathophysiology and clinical treatment of ITP has been confirmed. Myeloid-derived suppressor cells (MDSCs) are other immunosuppressive cells, which can also suppress T cell activation by secreting arginase, iNOS and ROS, and are essential for Treg cells' differentiation and maturation. Therefore, we speculate that MDSCs might also be involved in the immune-dysregulation mechanism of ITP. In this study, we tested MDSCs and Treg cells in peripheral blood samples of twenty-five ITP patients and ten healthy donors. We found that MDSCs and Treg cells decreased simultaneously in active ITP patients. Relapsed ITP patients showed lower MDSCs levels compared with new patients. All patients received immunosuppressive treatment including dexamethasone alone or in combination with intravenous immune globulin. We found that MDSCs' level after treatment correlated with platelet recovery. Our study is the first that focused on MDSCs' role in ITP. Based on our results, we concluded that circulating MDSCs could predict disease activity and treatment response in ITP patients. This preliminary conclusion indicates a substantial significance of MDSCs in the pathophysiology and clinical treatment of ITP, which deserves further investigation.

Zika virus (ZIKV) infection related with immune thrombocytopenic purpura (ITP) exacerbation and antinuclear antibody positivity.

A 30-year-old Colombian woman with past history of immune thrombocytopenia (ITP) presented to the emergency room with two days of global headache, arthralgia, myalgia, and low level fever and generalized erythematous rash. Platelets dropped to 9 × 109/L (fourth day of symptoms) without hemorrhagic manifestations but recovered to 30 × 109/L in 24 hours (fifth day). Dengue virus infection, as well as other viral infections, was ruled out. Zika virus (ZIKV) was evaluated in serum and urine samples by real-time reverse-transcriptase polymerase chain reaction (genomic regions within E protein and NS2b protein). Urine sample was positive and serum sample negative for ZIKV, confirming a recent ZIKV infection with urinary tract virus excretion at 7th day after disease onset. To our knowledge this is the first description of a case of severe immune thrombocytopenia exacerbation and antinuclear antibody positivity induced by ZIKV infection.

Circulating myeloid-derived suppressor cells predict disease activity and treatment response in patients with immune thrombocytopenia

Immune thrombocytopenia (ITP) is a disease characterized by isolated thrombocytopenia. Abnormal effector T cell activation is an important mechanism in the pathogenesis of ITP. Regulatory T cells (Treg) have a strong immunosuppressive function for T cell activation and their importance in the pathophysiology and clinical treatment of ITP has been confirmed. Myeloid-derived suppressor cells (MDSCs) are other immunosuppressive cells, which can also suppress T cell activation by secreting arginase, iNOS and ROS, and are essential for Treg cells’ differentiation and maturation. Therefore, we speculate that MDSCs might also be involved in the immune-dysregulation mechanism of ITP. In this study, we tested MDSCs and Treg cells in peripheral blood samples of twenty-five ITP patients and ten healthy donors. We found that MDSCs and Treg cells decreased simultaneously in active ITP patients. Relapsed ITP patients showed lower MDSCs levels compared with new patients. All patients received immunosuppressive treatment including dexamethasone alone or in combination with intravenous immune globulin. We found that MDSCs’ level after treatment correlated with platelet recovery. Our study is the first that focused on MDSCs’ role in ITP. Based on our results, we concluded that circulating MDSCs could predict disease activity and treatment response in ITP patients. This preliminary conclusion indicates a substantial significance of MDSCs in the pathophysiology and clinical treatment of ITP, which deserves further investigation.

Platelet Apoptosis in Adult Immune Thrombocytopenia: Insights into the Mechanism of Damage Triggered by Auto-Antibodies.

Mechanisms leading to decreased platelet count in immune thrombocytopenia (ITP) are heterogeneous. This study describes increased platelet apoptosis involving loss of mitochondrial membrane potential (ΔΨm), caspase 3 activation (aCasp3) and phosphatidylserine (PS) externalization in a cohort of adult ITP patients. Apoptosis was not related to platelet activation, as PAC-1 binding, P-selectin exposure and GPIb-IX internalization were not increased. Besides, ITP platelets were more sensitive to apoptotic stimulus in terms of aCasp3. Incubation of normal platelets with ITP plasma induced loss of ΔΨm, while PS exposure and aCasp3 remained unaltered. The increase in PS exposure observed in ITP platelets could be reproduced in normal platelets incubated with ITP plasma by adding normal CD3+ lymphocytes to the system as effector cells. Addition of leupeptin -a cathepsin B inhibitor- to this system protected platelets from apoptosis. Increased PS exposure was also observed when normal platelets and CD3+ lymphocytes were incubated with purified IgG from ITP patients and was absent when ITP plasma was depleted of auto-antibodies, pointing to the latter as responsible for platelet damage. Apoptosis was present in platelets from all patients carrying anti-GPIIb-IIIa and anti-GPIb auto-antibodies but was absent in the patient with anti-GPIa-IIa auto-antibodies. Platelet damage inversely correlated with platelet count and decreased during treatment with a thrombopoietin receptor agonist. These results point to a key role for auto-antibodies in platelet apoptosis and suggest that antibody-dependent cell cytotoxicity is the mechanism underlying this phenomenon.

Novel hypomorphic mutation in IKBKG impairs NEMO-ubiquitylation causing ectodermal dysplasia, immunodeficiency, incontinentia pigmenti, and immune thrombocytopenic purpura.

NF-κB essential modulator (NEMO) is a component of the IKK complex, which participates in the activation of the NF-κB pathway. Hypomorphic mutations in the IKBKG gene result in different forms of anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) in males without affecting carrier females. Here, we describe a hypomorphic and missense mutation, designated c.916G>A (p.D306N), which affects our patient, his mother, and his sister. This mutation did not affect NEMO expression; however, an immunoprecipitation assay revealed reduced ubiquitylation upon CD40-stimulation in the patient's cells. Functional studies have demonstrated reduced phosphorylation and degradation of IκBα, affecting NF-κB recruitment into the nucleus. The patient presented with clinical features of ectodermal dysplasia, immunodeficiency, and immune thrombocytopenic purpura, the latter of which has not been previously reported in a patient with NEMO deficiency. His mother and sister displayed incontinentia pigmenti indicating that, in addition to amorphic mutations, hypomorphic mutations in NEMO can affect females.

Roles of peripheral B1 cells in the individualized treatment of adult idiopathic thrombocytopenic purpura.

We aimed to explore the changes of peripheral B1 cells before and after treatment of adult idiopathic thrombocytopenic purpura (ITP) and to investigate the association of these changes with the disease condition and prognosis. Ninety-seven ITP patients were divided into the effective or ineffective groups, based on their response to hormone therapy. Forty healthy volunteers were enrolled into the control group (HC). The percentages of CD19+ cells, B1 cells, and platelet-associated immunoglobulin (PAIg) in peripheral blood from healthy volunteers and ITP patients before and after treatment were evaluated, and blood platelet (PLT) counts were determined. The percentages of CD19+ cells [(21 ± 10.0) vs (11.2 ± 7.1)%], B1 cells [(8.85 ± 5.23) vs (2.2 ± 1.3)%], and PAIg [(28 ± 19) vs (11.7 ± 8)%] in whole blood from ITP patients before treatment were significantly higher than those in whole blood from healthy controls (P < 0.05). Before treatment, the percentage of B1 cells and PAIg in ITP patients was negatively correlated with the PLT level (r = -0.89, P < 0.05 and r = -0.814, P < 0.05, respectively). Further, the B1 cell percentage was positively associated with the PAIg percentage in ITP patients before treatment. In the effective group, the B1 cell percentage was reduced sharply at 1 month after treatment [(2.45 ± 1.75) vs (8.74 ± 5.04)%, P < 0.05)], so as at 3 and 6 months. However, in the ineffective group, there was no difference in the B1 cell percentage before and after treatment [(7.9 ± 5.6) vs (8.76 ± 5.26)%]. This obvious association of changes in peripheral B1 cells with disease condition and prognosis in ITP patients may be of certain clinical significance for guiding the individualized treatment of ITP.

Helicobacter pylori infection & immune thrombocytopenic purpura in children and adolescents: A randomized controlled trial.

Helicobacter pylori and immune thrombocytopenic purpura (ITP) association is not well established in chronic ITP (cITP) in children, although the cure of thrombocytopenia in approximately half of H. pylori eradicated adult patients has been described. The aim of this study was to investigate the effect of H. pylori eradication on platelet (PLT) recovery in cITP children and adolescents through a randomized, controlled trial. A total of 85 children (mean age 11.4 years) with cITP were prospectively enrolled. Diagnosis of H. pylori was established by two locally validated tests, (13)C-urea breath test and monoclonal stool antigen test. Twenty-two infected patients were identified, and randomly allocated into two groups: H. pylori treatment group (n = 11) and the non-intervention control group (n = 11). The control group was offered treatment if the thrombocytopenia persisted after the follow-up. At baseline, there were no differences regarding age, sex, duration of disease, and PLT count between groups. Sixty three of 85 patients were uninfected. PLT response was classified as complete response: PLT > 150 × 10(9 )l(-1); partial response: PLT 50-150 × 10(9 )l(-1), or an increase of 20-30 × 10(9 )l(-1); no response: PLT < 50 × 10(9 )l(-1) or an increase of <20 × 10(9 )l(-1) after at least 6 months of follow-up. Complete response was observed in 60.0% (6/10, one excluded) H. pylori eradicated patients vs. 18.2% (2/11) in non-eradicated patients (p = 0.08; OR = 6.75) after 6-9 months of follow-up. Among uninfected patients, only 13.8% (8/58) presented complete response. Two non-treated controls were treated after 6-12 months of follow-up, and PLT response was observed in 61.5% (8/13) of H. pylori eradicated patients, and in 19.0% (11/58) of uninfected patients (p = 0.004). Cytotoxin associated gene A and vacuolating cytotoxin gene A IgG antibodies were present in almost all infected patients. Therefore, the study suggests that H. pylori eradication plays a role in the management of H. pylori infected cITP children and adolescents.

Cytokine profile of patients with chronic immune thrombocytopenia affects platelet count recovery after Helicobacter pylori eradication.

Helicobacter pylori eradication induces platelet recovery in a subgroup of patients with chronic immune thrombocytopenia (cITP), but the mechanisms involved are still not understood. We aimed to evaluate the effect of H. pylori eradication on platelet response and to identify the associated serum cytokine profile in 95 patients with cITP. Serum cytokine concentrations were determined by enzyme-linked immunosorbent assay prior to and 6 months after H. pylori eradication. Remission of cITP was observed in 17 (28·8%) of 59 patients in whom the bacterium was eradicated. Six months after treatment, a significant reduction in the concentrations of T-helper (Th) 1 and Th17 cells and an increase in T regulatory (Treg) and Th2-cell commitment cytokines were observed in patients who recovered, but not in those whose platelet count did not recover. Patients who had a platelet response to eradication of the bacteria had higher pre-treatment serum levels of γ-interferon (IFNG, IFN-γ), transforming growth factor-ß (TGFB1, TGF-ß) and interleukin 17 (IL17A, IL-17) than patients who did not respond, but only higher pre-treatment TGFB1 levels was independently associated with platelet response. In conclusion, amelioration of cITP after eradication of H. pylori was linked to a more efficient suppression of Th1 and Th17 response and a more pronounced Treg cell response.

Impaired proplatelet formation in immune thrombocytopenia: a novel mechanism contributing to decreased platelet count.

The pathophysiological mechanisms contributing to the decreased platelet count in immune thrombocytopenia (ITP) are not entirely understood. Here, we investigated the key step of proplatelet formation (PPF) by studying the effect of ITP plasma in thrombopoiesis. Normal cord blood-derived mature megakaryocytes were cultured in the presence of recalcified plasma from ITP patients, and PPF was evaluated by microscopic analysis. Patient samples induced a dose-dependent inhibition in PPF, as well as decreased complexity of proplatelet architecture. Although slightly increased, plasma-induced megakaryocyte apoptosis was not related to PPF impairment. Purified IgG reproduced the inhibitory effect, while platelet-adsorbed plasma induced its reversion, suggesting the involvement of auto-antibodies in the inhibition of thrombopoiesis. Impaired PPF, induced by ITP plasmas bearing anti-GPIIb-IIIa antibodies, was related to their ability to interfere with the normal function of this integrin, as assessed by megakaryocyte PAC-1 binding and ß3 integrin phosphorylation while the presence of anti-glycoprotein Ia-IIa auto-antibodies was associated with loss of normal inhibition of PPF induced by type I collagen. In conclusion, abnormal thrombopoiesis comprising decreased PPF and morphological changes in proplatelet structure are induced by patient samples, unveiling new mechanisms contributing to decreased platelet count in ITP.

Immune thrombocytopenia with antiphospholipid antibodies in monozygotic twins.

We describe monozygotic twins with immune thrombocytopenia (ITP) associated to antiphospholipid antibodies with a dissimilar clinical expression. The first patient was diagnosed to have ITP at 63 years old and was treated with corticosteroids. She presented ulterior exacerbations of thrombocytopenia requiring intravenous immunoglobulin and subsequent treatment with rituximab. She ultimately had a favorable response without thrombotic events during follow-up. The second patient who had a history of three spontaneous abortions and endometrial adenocarcinoma in complete remission was evaluated for severe thrombocytopenia, ITP was diagnosed at the age of 63. She was treated with steroids and had a favorable response. After few months she developed deep venous thrombosis and pulmonary embolism requiring anticoagulation therapy without hemorrhagic events. Both patients were found to have antiphospholipid antibodies and HLA DR4 (DRB1*04) and HLA DR5 (DRB1*12). The association of those two entities in monozygotic twins could support the presence of common predisposing genes. However, with both patients being genotipically identical, the clinical expression was different. Those cases highlight the possibility that environmental factors may affect the expression of those disorders.

The levels of IL-17A and of the cytokines involved in Th17 cell commitment are increased in patients with chronic immune thrombocytopenia.

Th17 cells have been associated with immune-mediated diseases in humans but it has still not been determined whether they play a role in immune thrombocytopenia. We evaluated representative cytokines of the Th17, Th1, Th2 and Treg cell commitment in the serum of patients with chronic immune thrombocytopenia, as well as the cell source of IL-17A. Higher levels of IL-17A and Th17-related cytokines, and an increased percentage of IL-17A producing CD4+ and neutrophils were observed in patients. The levels of cytokines involved in Th1 cell commitment IFN-γ, IL-2, IL12-p70 and the percentages of Th1 cells were also increased, but IL-4 was not detected. Although the concentrations of IL-10 were higher, the levels of TGF-ß were similar in both groups. In conclusion, our results point to a putative role for Th-17 cells/IL-17A cytokine in the pathogenesis of chronic immune thrombocytopenia.

IL1RN VNTR and IL2-330 polymorphic genes are independently associated with chronic immune thrombocytopenia.

Chronic Immune Thrombocytopenia (cITP) is an acquired immune-mediated disease associated with a T-helper cell type 1 (Th1) immune polarization, whose genetic risk factors, however, are largely unknown. We investigated polymorphisms in promoter regions of genes that code molecules involved in proinflammatory immune response [IL1B-31T/C, IL1RN variable number tandem repeats (VNTR), IL2-330T/G, and TNF-307G/A] as well as in genes that code Toll like receptors (TLR) (TLR2 Arg753Gln, TLR4 Asp299Gly and TLR5 Arg(392stop)) in 122 patients with cITP and 541 blood donors. The frequencies of the IL1RN polymorphic allele 2 (P = 0·001) and of the IL2-330 polymorphic allele G (P =0·004) were significantly higher in cITP patients than in blood donors. In logistic analysis adjusting for age and gender, the polymorphisms remained independently associated with cITP. Enhanced serum concentrations of interleukin (IL)-1α and IL-1ß were observed in cITP (P < 10(-3) ) and blood donor (P = 0·04) carriers of the IL1RN*2. Also, the serum levels of IL-2 and γ-interferon (IFN-γ) were increased in cITP patients (P < 10(-3) and P = 0·04 respectively) and blood donors (P < 10(-3) and P = 0·03 respectively) harbouring the IL2-330G allele. Here we demonstrated that IL2-330G and IL1RN*2 are independently associated with cITP and are functional in vivo, which strongly suggests that they contribute to the pathogenesis of cITP.

Idiopathic thrombocytopenic purpura and oral surgery: case report / Púrpura trombocitopênica idiopática e cirurgia bucal: relato de caso

OBJECTIVES: To review the function of platelets in the blood clotting mechanism. To address,conceptualize and classify thrombocytopenic purpura, especially idiopathic thrombocytopenic purpura (ITP),emphasizing the immunological aspects involved in the etiology of the disease. To address the clinicalmanifestations of the disease and the appropriate therapy. To present the case study of a patient with ITPwho requires oral surgical intervention. DISCUSSION: Leukopenia in ITP can be subclinical. The firstmanifestation of the disease can be severe hemorrhaging due to small lacerations or minor medical anddental surgical procedures. The cause of the platelet reduction is idiopathic; an autoimmune reaction in whichthe antibodies destroy the platelets appears to participate in the process. A variety of situations can occur,leading to mild to severe thrombocytopenia. One frequent aspect is the instability of the platelet count,which oscillates inconsistently and may be related to infections and other factors that have not been clearlydetermined, including stress. In the case presented here, the leukopenia in the patient was mild in presentation.However, it was decided that the patient should be referred to a hematologist for preparation and clearance.Oral surgery that compromises the bone, such as exodontia, can present significant difficulties in localizingand clamping intraosseous vessels, which does not only occur in small soft tissue surgeries. CONCLUSIONS:Platelet destruction in ITP occurs from a complex process that is comprised of multiple components of theimmune system. The platelets are prematurely destroyed by antibodies that are aimed at the platelet glycoprotein,which can results in serious, even fatal consequences. It is important to emphasize the significance of themedical history and the appropriate physical examination during the diagnostic process, as well as collaborationwith the patient’s medical...

OBJETIVOS: Revisar a função das plaquetas no mecanismo de coagulação sanguínea. Conceituare classificar a púrpura trombocitopênica, especialmente a púrpura idiopática, enfatizando osaspectos imunológicos envolvidos na etiologia da doença. Enfocar as manifestações clínicas dadoença e a terapia apropriada. Apresentar um caso de manifestação clínica da doença e a terapiaapropriada. Apresentar o caso de uma paciente com púrpura que necessitava de intervençãocirúrgica bucal. DISCUSSÃO: A leucopenia na púrpura trombocitopênica idiopática pode sersubclínica. A primeira manifestação da doença pode ser uma hemorragia severa por causa depequenas lacerações ou pequenos procedimentos médicos e odontológicos. A causa da reduçãodas plaquetas é idiopática; uma reação autoimune na qual os anticorpos destroem as plaquetasparece participar do processo. Uma variedade de situações pode ocorrer, levando àtrombocitopenia discreta a severa. Um aspecto frequente é a instabilidade da contagem plaquetária,que oscila inconsistentemente e pode relacionar-se com infecções e outros fatores ainda nãoclaramente determinados, incluindo estresse. No presente caso, o paciente apresentava discretaleucopenia. Entretanto, decidiu-se que o paciente deveria ser avaliado por um hematologista,para preparação e liberação para cirurgia, pois a cirurgia bucal que compromete osso, como aexodontia, pode apresentar dificuldades significativas na localização e pinçamento de vasosintraósseos, o que não acontece em pequenas cirurgias de tecidos moles. CONCLUSÕES: Adestruição plaquetária na púrpura trombocitopênica ocorre por meio de um complexo processo,com múltipos componentes do sistema imune. As plaquetas são destruídas prematuramente poranticorpos dirigidos contra as glicoproteínas plaquetárias, o que pode resultar em sérias – emesmo fatais – consequências. É importante enfatizar o significado da história médica e o examefísico adequado no processo diagnóstico...

[Treatment of chronic immune thrombocytopenic purpura. Looking for something better. Review]. / Tratamiento de la púrpura trombocitopénica inmune crónica. Buscando algo mejor. Revisión.

Chronic Immune Thrombocytopenic Purpura (cITP) has become a field of multiple therapeutic assays. More than 20 types of treatment have been developed to obtain a favorable and prolonged platelet response. The treatment of cITP is oriented to inhibit the antiplatelet antibodies production by interference with the macrophage of the reticulum endothelial system and a blockade of the antigenic response with a decrease in the amplification of the immunological response. Steroids of the glucocorticoids type and splenectomy constitute the first line of treatment. Failure of these treatments leads to the use of second line drugs such as non steroid immuno-supressors and the immunoglobulins type IgG and anti-D. Therapeutic assays with others immunomodulators have been reported. The introduction of new drugs destined to increase the megakaryocytic bone marrow platelet production, has opened a new way to treat the cITP. However, the splenectomy remains as the simplest, safest and most effective treatment in cITP. The principal criteria does not have to be focused on obtaining a normal platelet count, but to reach safe hemostatic levels in absence of hemorrhage, for a prolonged time. On the other hand, despite the persistence of thrombocytopenia, the hematologist can choose to maintain the patient with no treatment and with only a strict clinical observation. It is obvious that the cost-benefit from the different treatments is inclined towards those of lower cost and minimal secondary effects.

Predisposition to idiopathic thrombocytopenic purpura maps close to the major histocompatibility complex class I chain-related gene A.

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune condition with poorly known etiology, characterized by platelet destruction. Genetic association studies of this disease are scarce, discrepant, and restricted to major histocompatibility complex (MHC) polymorphisms. Hence, a case-control study was conducted with an aim to map the MHC to IPT susceptibility using HLA-B and nine microsatellite loci encompassing MHC class I, II, and III regions. We compared the allelic frequencies in samples of unrelated healthy controls and ITP patients. After correction for multiple tests, only allele MICA*183, also known as A5.1, demonstrated an association, resulting in the identification of a major predisposing region close to STR-MICA. This result may highlight the putative functional role of MICA in the immune response to ITP.