Suspects in the tale of lupus-associated thrombocytopenia

Immunologically mediated thrombocytopenia is a frequent clinical manifestation in patients with systemic lupus erythematosus (SLE). Autoantibodies targeting platelet membrane glucoproteins have a central role in peripheral platelet destruction. Autoantibodies against thrombopoietin are also present in about one‐third of patients, but their pathogenetic role is obscure. Thirty‐eight serum samples from SLE patients were tested for anti‐platelet antibodies, anti‐thrombopoietin antibodies and levels of circulating thrombopoietin. Bone marrow histology was also assessed. Thirty‐nine per cent of sera displayed anti‐thrombopoietin antibodies and 29% had circulating anti‐platelet antibodies. Anti‐thrombopoietin antibodies were associated with lower thrombopoietin concentrations, and lower mean platelet values in long‐term follow‐up. Anti‐platelet antibodies were present in about 40% of thrombocytopenic and non‐thrombocytopenic individuals but were absent in patients who had recovered from thrombocytopenia, supporting their pathogenetic role. Both autoantibodies were absent in control sera from patients with rheumatoid arthritis and primary Sjögren’s syndrome. Decreased bone marrow cellularity, normal or low number of hypolobulated, pyknotic megakaryocytes and stromal alterations were prominent findings in thrombocytopenic SLE patients, suggesting a defect in megakaryopoiesis. These findings were not evident in specimens from patients with idiopathic thrombocytopenic purpura who had increased megakaryocytes, normal cellularity and absence of stromal alterations. In conclusion, peripheral destruction due to platelet autoantibodies, anti‐thrombopoetin antibodies, lower effective circulating thrombopoetin and impaired compensatory response due to bone marrow damage interact in SLE and thrombocytopenia ensues.     

Immunopathology of thrombocytopenia in experimental malaria.

An early thrombocytopenia was observed in CBA mice during acute infection with Plasmodium berghei. This was associated with an increase in bone marrow megakaryocytes and a reduction of normal syngeneic 111Indium-labelled platelet life span. Malaria-induced thrombocytopenia was thus considered to be the result of increased peripheral platelet destruction rather than central hypoproduction. The occurrence of thrombocytopenia was modulated by T-cell depletion. Indeed, thymectomized, irradiated or anti-CD4 monoclonal antibody-treated mice failed to develop thrombocytopenia, although they were infected to the same extent. Conversely, a significant thrombocytopenia was observed in thymectomized mice reconstituted with CD4+ T cells. During the course of infection, a significant inverse correlation was found between platelet counts and platelet-associated IgG. Normal mice passively transferred with serum from syngeneic malaria-infected mice developed thrombocytopenia. The possibility to raise monoclonal anti-platelet antibodies from P. berghei-infected animals further suggested a role for an antibody-mediated platelet destruction during acute murine malaria infection. These results indicate that in murine malaria, thrombocytopenia is mediated by immune mechanisms and that CD4+ T cells might be significantly involved.     

Pathophysiology of HIV related thrombocytopenia: an analysis of 41 patients.

AIM--To analyse the pathogenic mechanism of HIV related thrombocytopenia. METHODS--Forty one patients with thrombocytopenia and HIV-1 infection were investigated over two years. Anticardiolipin antibodies were measured using an enzyme linked immunosorbent assay and antiplatelet antibodies were measured using an immunocapture technique. Tests for VDRL, C3 and C4, antinuclear antibodies and rheumatoid factor were also carried out in all patients and 80 control subjects (HIV-1 positive but non-thrombocytopenic). Indiumoxine labelled platelets were transfused in 13 patients. P24 antigen were also measured in 12 bone marrow aspirates. RESULTS--Antiplatelet antibodies and circulating immune complexes were found exclusively in the thrombocytopenic group; values for antiplatelet antibodies and circulating immune complexes were both higher in homosexual and bisexual patients. Three kinds of pattern were observed using 111 In-labelled platelets: splenic (n = 10); hepatic (n = 2); and destruction of bone marrow in just one case. The two most influential factors in the sequestration pattern were antiplatelet antibodies in the splenic uptake and circulating immune complexes in the hepatic and marrow sequestration. All patients, except three, had decreased platelet recovery. In those patients with a CD4 lymphocyte count of less than 200 x 10(6) cells/l the recovery was clearly greater (53%) than in patients who had more than 200 x 10(6) /l (28%). Finally, in seven of the 12 patients who were chosen for immunohistochemical study, p24 antigen was detected in the megakaryocytes, verifying that HIV-1 infects such cells. CONCLUSIONS--The pathogenic mechanism of HIV related thrombocytopenia is probably multifaceted. Antiplatelet antibodies and circulating immune complexes would cause peripheral destruction in the spleen, liver, and bone marrow, in that order; and, on the other hand, there would be an ineffective immune thrombopoiesis and direct infection of the megakaryocytes which could cause a change in the function and maturity of these cells.     

The platelet volume-number relationship in patients infected with the human immunodeficiency virus

The pathophysiology of thrombocytopenia in the acquired immune deficiency syndrome has not been elucidated completely. Many findings in these patients are identical to those with immune thrombocytopenic purpura. However, recent findings in acquired immune deficiency syndrome patients including the effect of zidovudine on platelet count and the demonstration of ultrastructural changes and viral RNA in megakaryocytes, have suggested that the human immunodeficiency virus may directly infect megakaryocytes, and play a role in acquired immune deficiency syndrome-related thrombocytopenia. To investigate further the mechanism of decreased platelet counts in human immunodeficiency virus-infected patients, the platelet volume-number relationship and corresponding bone marrow findings in 34 patients infected with human immunodeficiency virus were studied. Parameters evaluated included platelet count and mean platelet volume; bone marrow cellularity, megakaryocyte number, and number and percentage of denuded megakaryocyte nuclei. Two thirds of the platelet counts were low, and of these 92% had an inappropriately low mean platelet volume. These individuals had a platelet-volume number relationship that is very similar to that seen in myelosuppressive disorders. In addition, more than 90% of the bone marrows from thrombocytopenic patients had either normal or decreased numbers of megakaryocytes. These observations provide additional evidence to support the hypothesis that the pathophysiology of human immunodeficiency virus-associated thrombocytopenia may be due, at least in part, to a direct effect on the megakaryocytes.     

Pathogenesis of immune thrombocytopenia in common variable immunodeficiency

Immune Thrombocitopenic Purpura (ITP) is an autoimmune disease characterized by antibody-mediated platelet destruction and variable reduced platelet production. Besides antibody-mediated platelet destruction, new pathogenic mechanisms have been reported to be involved in reducing platelet count. Among these, desialylation is one of the most recent and innovative mechanisms that has been found to be implied, at least in part, in non-antibody mediated platelet clearance.Common Variable Immunodeficiency (CVID) is the most common Primary Immunodeficiency seen in clinical practice. About 25–30% of CVID patients are affected by autoimmune manifestation, among which ITP is the most common. Little is know about pathophysiological mechanisms that lead to ITP in CVID.Given the poor antibody production typical of CVID patients, we aimed at verifying whether platelet desialylation could be responsible for CVID associated thrombocytopenia.According to our results, we may suggest that in CVID patients, ITP is due to a decreased bone marrow platelets production, rather than an increased peripheral platelet destruction, which is more common in patients with primary ITP. An increased platelet desialylation does not appear to be implicated in the thrombocytopenia secondary to CVID, while it is implicated in the pathogenesis of primary ITP. Nevertheless an intriguing aspect has emerged from this study: regardless the presence of thrombocytopenia, the majority of CVID patients present a double platelet population as far as desialylation concerns, whilst no one of the healthy donors and of the patients with primary ITP shows a similar characteristic.     

系统性红斑狼疮重症血小板减少患者血清对巨核祖细胞的影响

研究系统性红斑狼疮(SLE)合并重症血小板患者的血清对正常人巨核祖细胞增殖分化的影响。以12例SLE重症血小板减少患者为研究对象,12份正常骨髓单个核细胞,培养中分别加入患者血清或灭活补体的患者血清,免疫化学染色检测巨核细胞克隆形成单位(CFU-MK),流式细胞仪检测CD41+细胞数。结果是正常对照组骨髓CFU-MK集落数为(61.22±29.71)个/片,加入SLE重症血小板减少患者血清后减少为(29.44±23.35)个/片,P<0.05;加灭活补体血清后减少为(22.56±15.21)个/片,与正常对照相比P<0.05;灭活补体与否差异不显著,P>0.05。加入患者血清或灭活补体的血清后,CD41+细胞数由正常(2.30%±1.63%)分别减少为(1.15%±0.85%)和(1.07%±0.76%),与正常对照相比P<0.05;灭活补体与否差异不显著。SLE血小板正常但活动期病人的血清对正常人CFU-MK和CD41+细胞的生成均无显著抑制。提示SLE重症血小板减少患者血清能抑制正常人骨髓巨核祖细胞的增殖分化,这种抑制作用是非补体依赖性的。     

Passive neonatal thrombocytopenia. A case study of factors predicting the response to i.v. IgG therapy

A term male infant was noted at birth to have petechiae over the face and trunk and a platelet count of 3 x 10(9) per L. Maternal immune thrombocytopenia (ITP) was suspected from the clinical data and confirmed by the presence of antiplatelet antibody (both in the mother and infant) detected by recently described flow cytometry method. Initial treatment with exchange transfusions, platelet transfusions, steroids, failed to correct thrombocytopenia and, hence, seven doses of high-dose gamma globulin (IV-IgG) were given intravascularly. Initiation of IV-IgG was followed by stabilization of platelet counts with marked reduction in the need for platelet transfusions. In this case of passive ITP, the therapeutic efficiency of high dose IV-IgG seems to depend upon maintaining a certain critical level of serum IgG (which in turn may depend upon the serum antiplatelet antibody titers).     

Immune amegakaryocytic thrombocytopenia of the newborn: association with anti-HLA-A2.

Three newborn babies with congenital immune amegakaryocytic thrombocytopenia are described. Two were siblings. The mothers' sera showed antibody against both pooled random platelets and lymphocytes of type HLA-A2. Two babies had transient thrombocytopenia and leucopenia and made a full haematological recovery. One baby died aged four hours having had no haematological investigations during life. Histological examination of the bone marrow in all three babies (two by trephine biopsy; one at necropsy) confirmed a deficiency of megakaryocytes. It is suggested that anti-HLA-A2 may cause neonatal thrombocytopenia by depressing megakaryocytes instead of, or in addition to, any direct effect on platelets.     

Thrombocytopenia due to defective platelet production

An increasing number of kindreds with thrombocytopenia have been described in the past decade as platelet counts have been done regularly. These patients are delineated from ITP, recognizing that some patients with hereditary thrombocytopenia may benefit from splenectomy. Until more information on platelet biochemical information is available, these disorders have been categorized by platelet size, now quantifiable as mean platelet volume (MPV). The availability of rapid and quantitative measurement of platelet count and MPV allow a better understanding of megakaryocyte proliferation and platelet production. The evolving changes of MPV during treatment and recovery from chemotherapy will now allow a forecast of marrow hypoplasia, since the platelet count and increase in MPV follow the increase in megakaryocyte ploidy to herald marrow regeneration. It is anticipated that the careful plotting of the MPV relationship to the platelet count will allow the physician to evaluate marrow function indirectly, in many cases replacing repeated bone marrow studies.     

Plasma glycocalicin. An aid in the classification of thrombocytopenic disorders

In some patients with thrombocytopenia, it is difficult to determine whether the condition is caused by underproduction of platelets (reduced numbers of megakaryocytes) or an increase in the rate of their destruction (normal or increased numbers of megakaryocytes). A non-invasive test to help distinguish between these two categories of thrombocytopenia would be useful. We related the plasma concentration of glycocalicin, a fragment of the platelet-membrane glycoprotein Ib, to the mechanism of thrombocytopenia by evaluating bone marrow megakaryocyte content and measuring platelet life span. Plasma glycocalicin was measured with a monoclonal antibody to the glycocalicin component of platelet glycoprotein Ib. The mean (+/- SD) plasma concentration of glycocalicin in 34 healthy controls was 87 +/- 20 percent of the level in pooled normal plasma (range, 52 to 127 percent). All of eight patients with aplastic anemia or amegakaryocytic thrombocytopenia confirmed by examining bone marrow (in all patients) and by determining the life span of autologous platelets (in six patients) had glycocalicin levels significantly below the normal range (5 to 27 percent). In contrast, each of 25 patients with thrombocytopenia thought to be caused by a reduction in platelet life span, whose bone marrow contained normal or increased numbers of megakaryocytes, had glycocalicin levels that fell within or above the normal range (48 to 261 percent). There was no overlap of values between the two patient populations. These studies indicate that the measurement of plasma glycocalicin may be a useful adjunct in classifying thrombocytopenic disorders.     

Platelet turnover and megakaryocytopoiesis in ITP

Among patients with ITP, a group of 9 subjects displayed a reduced platelet turnover. In their bone marrow the megakaryocyte mass was measured by 59Fe, and the results were referred to those of 6 patients with a moderately increased and of 6 with a considerably increased platelet turnover. In the low-turnover group the megakaryocyte nuclear lobe number was subnormal cells with basophil cytoplasm were in the majority and the number of megakaryocytes was increased, whereas in the other two groups of megakaryocite population showed a shift to the right, and increased nuclear lobe number, and the number of megakaryocytes, related to the erythroid cells, was increased. It is therefore assumed that in the case of a reduced platelet turnover, the megakaryocytes are damaged, primarily their maturation in the bone marrow. The three groups showed, however, no clinical differences.     

Review: immune thrombocytopenic purpura: an update for immunohematologists

Immune thrombocytopenic purpura (ITP) is an acquired disease in which autoantibodies to platelets cause their sequestration and destruction by mononuclear macrophages, principally in the spleen. If increased production of platelets by megakaryocytes does not compensate for platelet destruction, the number of circulating platelets decreases (thrombocytopenia), resulting in a characteristic bleeding tendency (purpura). While most children with the disease experience a relatively short and benign clinical course, ITP in adults often lasts more than 6 months (chronic ITP) and is resistant to conventional treatment (corticosteroids, intravenous immune globulin, or splenectomy). The goal of medical management is to increase the platelet count to a safe level, without the risks of bacterial infections associated with splenectomy or toxicity from prolonged corticosteroid therapy. Splenectomy increases platelet counts in hours to days in most patients with acute ITP, but nearly 50 percent experience recurrent thrombocytopenia by 5 years postsplenectomy.     

Target platelet antigen in homosexual men with immune thrombocytopenia

A syndrome of isolated immune thrombocytopenic purpura (ITP) has recently been described in homosexual men. We have identified an antiplatelet antibody in the serum of 29 of 30 homosexual men with isolated ITP. The antibody binds to a platelet membrane antigen of 25,000 daltons, and binding is effected by the F(ab)2 portion of the immunoglobulin. Similar antibody activity was not detected in serum from 30 nonhomosexual patients with either ITP or nonimmune thrombocytopenia. The 25,000-dalton antigen was not found on other hematopoietic cells, and it was distinct from the core protein of the AIDS-associated retrovirus. In contrast, serum antibody reacted with a 25,000-dalton antigen associated with cultured herpes simplex virus Types I and II. In these experiments the antigen appeared to be derived from green-monkey kidney cells in which the herpes simplex viruses were grown. Identical antigenic activity was also demonstrated in uninfected human skin fibroblasts. We conclude that ITP in homosexual men is accompanied by a serum antibody directed against a platelet antigen of 25,000 daltons. The nature of the antigen and the relation of the serum antibody to ITP require further study.     

The role of HLA antibodies in neonatal thrombocytopenia: a prospective study

The role of HLA antibodies in neonatal alloimmune thrombocytopenia is controversial. We prospectively studied the sera of obstetric patients at delivery for HLA antibodies and correlated their presence with umbilical cord blood platelet counts. We studied 493 births at The Johns Hopkins Hospital comprising of 357 African American, 115 Caucasian, and 21 babies of other racial groups. One hundred and thirty nine mothers had HLA antibodies. Of these HLA alloimmunized mothers, only ten infants had platelet counts of 150,000/μL or less. Three hundred and eight mothers with no detectable antibodies gave birth to 27 infants with platelet counts of 150,000/μL or less. Yates corrected Chi square analysis showed no significant relationship between maternal HLA alloimmunization and baby platelet count (p=0.709). Only 8 of sixty cord sera from babies of HLA alloimmunized mothers were positive for HLA antibodies. The HLA cord blood antibody results were then correlated with the neonatal platelet counts. The Fisher's exact test showed no significant relationship between the presence of HLA antibodies in cord blood samples and neonatal platelet counts (p=0.232). Although one third (31%) of mothers have HLA antibodies, neonatal thrombocytopenia is rarely associated with this finding. However, HLA antibodies can cross the placenta, and in these unusual cases, may be associated with a higher risk of neonatal thrombocytopenia.     

射频消融治疗顽固性免疫性血小板减少症

目的探讨脾脏射频消融术治疗顽固性免疫性血小板减少症（ITP）的安全性和有效性。方法回顾分析我院开展的国际首例脾脏射频消融治疗ITP的疗效。结果 1例43岁女性食管癌患者,经反复外周血计数、血涂片和骨髓穿刺等检查证实合并原发性重症ITP,其血小板计数小于（5~10）×109/L,经规范抗幽门螺旋杆菌治疗、静滴人免疫球蛋白、甲基强的松龙、长春新碱和输注血小板等治疗无效。患者接受腹腔镜下脾脏射频消融术治疗,术后第22天血小板计数恢复正常,无围手术期并发症;随访超过8个月,患者呈完全应答。结论脾脏射频消融术治疗顽固性ITP安全、有效,值得扩大临床试验进一步验证其疗效。     

Anti-D immunoglobulin treatment for thrombocytopenia associated with primary antibody deficiency

AIMS: To review our experience of anti-D immunoglobulin for immune thrombocytopenia (ITP) in patients with primary antibody deficiency. METHODS/PATIENTS: A retrospective case notes review of four Rhesus positive patients with ITP and primary antibody deficiency, treated with anti-D. Patients were refractory to steroids and high dose intravenous immunoglobulin (IVIG). Two patients were previously splenectomised. RESULTS: All patients responded to anti-D immunoglobulin. Improved platelet counts were sustained for at least three months. Side effects included a fall in haemoglobin in all cases; one patient required red blood cell transfusion. Two patients had transient neutropenia (< 1 x 10(9)/litre). CONCLUSION: Anti-D immunoglobulin may be an effective treatment for antibody deficiency associated thrombocytopenia, even after splenectomy. Anti-D immunoglobulin may have considerable clinical advantages in this group of patients, where treatments resulting in further immunosuppression are relatively contraindicated.     

The incidence of thrombocytopenia in children with Cornelia de Lange syndrome

Thrombocytopenia was first reported in Cornelia de Lange syndrome (CdLS) by Froster in 1993. Despite early reports, thrombocytopenia has been rarely reported in this disorder. We performed a retrospective analysis of a large cohort of patients with CdLS. We calculated prevalence of thrombocytopenia in three subsets of this cohort: the entire cohort (n = 1,740), a subset of subjects with substantial clinical records (n = 695) and a subset of subjects with clinical information regarding platelet counts (n = 85). This analysis revealed that 15 have had thrombocytopenia (18% of those with available blood counts); seven had immune thrombocytopenia (ITP). The reported prevalence of pediatric ITP is between 5 and 13 per 100,000 persons. The prevalence of ITP in this cohort is between 7/1,740 and 7/85, giving a relative risk of ITP of between 30 (CI 12–77) and 633 (CI 259–1,549). Contrary to the reported cases in the literature, none of our patients have had progression of the thrombocytopenia nor have they developed other cytopenias. All 15 patients with thromobocytopenia had CdLS based on clinical criteria. Of the 10 patients tested for mutations in NIBPL, 8 had mutations identified. These data support an increased incidence of thrombocytopenia and ITP in CdLS. Subsequently, patients are at risk for spontaneous hemorrhage, and likely increased risk secondary to the high frequency of self‐injurious behavior. Although further studies are needed to better define the scope of the problem and to define the mechanisms of thrombocytopenia in CdLS, we would recommend screening for thrombocytopenia upon diagnosis and at 5‐year intervals thereafter. © 2010 Wiley‐Liss, Inc.     

Human/BALB radiation chimera engrafted with splenocytes from patients with idiopathic thrombocytopenic purpura produce human platelet antibodies.

We have previously shown that lethally irradiated normal strains of mice, radioprotected with severe combined immunodeficient (SCID) bone marrow, can be engrafted with human peripheral blood mononuclear cells (PBMC). The human/mouse radiation chimera can mount marked humoral and cellular responses to recall antigens, as well as primary responses. In the present study, we adoptively transferred splenocytes from patients with chronic immune thrombocytopenic purpura (ITP) into lethally irradiated BALB/c mice, radioprotected with SCID bone marrow. High titres of total human immunoglobulin appeared as early as 2 weeks post-transplant and declined after 6 weeks, while human anti-human platelet antibodies were detected 2-8 weeks after the transfer of splenocytes. The immunoglobulin G (IgG) fraction contained antibodies against glycoprotein (GP) IIb/IIIa (CD41) or GPIb/IX (CD42). The human platelet antibodies showed a low level of cross-reactivity with mouse platelets, and thrombocytopenia in the animals was not observed. Splenocytes from individual ITP patients differed in their capacity to produce either human platelet antibodies or total human immunoglobulin. Furthermore, antibodies produced in the murine system were not always identical to the original antibodies present in the serum of the patients. The study of the serological aspects of autoantibodies against human platelets in an animal model might be useful for the investigation of potential therapeutics in ITP.     

Kinetic studies of the mechanism of thrombocytopenia in patients with human immunodeficiency virus infection.

BACKGROUND. Isolated thrombocytopenia accompanied by increased amounts of platelet-associated antibody is a common manifestation of human immunodeficiency virus (HIV) infection, and the thrombocytopenia often improves with zidovudine. It is not clear whether the mechanism of HIV-related thrombocytopenia primarily involves autoimmune destruction of platelets or reduced platelet production by megakaryocytes. METHODS. We studied the survival of 111In-labeled autologous platelets and performed platelet imaging in 24 men with isolated HIV-related thrombocytopenia (16 who received no treatment and 8 who received zidovudine). We also studied 20 HIV-infected men with normal platelet counts (10 who received no treatment and 10 who received zidovudine) and studied 12 healthy seronegative men as controls. RESULTS. Mean (+/- SD) platelet survival was significantly decreased in both the untreated and the zidovudine-treated patients with HIV-related thrombocytopenia (to 92 +/- 33 and 129 +/- 44 hours, respectively; both P < 0.001), as compared with the normal controls (198 +/- 15 hours). Mean platelet survival was also significantly decreased in the HIV-infected patients with normal platelet counts (untreated, 162 +/- 23 hours, P < 0.01; zidovudine-treated, 166 +/- 35 hours, P < 0.05). Imaging studies, however, revealed no evidence of increased clearance of autologous platelets in the liver or spleen in any of these groups. Mean platelet production was significantly depressed in the untreated patients with thrombocytopenia (23,000 +/- 11,000 platelets per cubic millimeter per day, P < 0.001) as compared with the healthy controls (45,000 +/- 6,000 per cubic millimeter per day). Mean platelet production was significantly increased, however, in the men treated with zidovudine, both in those with thrombocytopenia (60,000 +/- 31,000 platelets per cubic millimeter per day, P < 0.01 vs. controls) and in those without thrombocytopenia (68,000 +/- 22,000 per cubic millimeter per day, P < 0.01). CONCLUSIONS. Although there was a moderate reduction in platelet survival in HIV-infected persons, these patients, regardless of platelet counts, also had decreased production of platelets, possibly due to viral infection of the megakaryocytes. Zidovudine appears to improve platelet production.