Stromal‐derived factor‐1 gene variations in pediatric patients with primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) of childhood is an autoimmune disease characterized by abnormally increased destruction of platelets and decreased megakaryopoiesis. Stromal‐derived factor‐1 (SDF‐1) plays a role in megakaryopoiesis and may be involved in the pathogenesis of ITP. Five single nucleotide polymorphisms (SNPs) of the SDF‐1 gene, including rs1801157, rs2839693, rs2297630, rs1065297, and rs266085, were assessed in 100 children with ITP and 126 healthy controls. The genotypes were analyzed by tetra ARMS polymerase chain reaction and confirmed by direct sequencing. Compared with controls, the rs2839693 A/A and rs266085 C/T genotypes were decreased in ITP patients (P = 0.004 and 0.007, respectively). The odds ratios of the latter genotypes were 0.48, 95% CI 0.28–0.82. Further analysis of the relationship between SDF‐1 polymorphisms and clinical features showed that rs2297630 A/G was associated with protection from chronicity (P = 0.002; OR, 0.07; 95% CI, 0.01–0.61) and steroid dependence (P = 0.007; OR, 0.10; 95% CI, 0.01–0.84) in ITP patients. However, rs266085 genotype C/C was associated with risk of steroid dependence (P = 0.012, OR 3.87, 95% CI 1.27–11.77). The findings of this study suggest that SDF‐1 gene variations may be associated with the occurrence and prognosis of childhood ITP.     

Vincristine efficacy and safety in treating immune thrombocytopenia: a retrospective study of 35 patients

Although vincristine (VCR) is sometimes prescribed for newly diagnosed immune thrombocytopenia (ITP), its efficacy in refractory ITP and sustained efficacy has yet to be demonstrated. We describe our clinical experience and recommend vincristine's correct place in ITP management. This retrospective study analysed data from 35 patients with newly diagnosed (ND), persistent (P) or chronic (C) ITP treated with VCR. The initial response rate, defined as >30 × 10⁹ platelets/L, reached 86% after a median of 7 [interquartile range (IQR) 6–13] days. In ND and P ITP, even when previous therapies were inefficient, initial response was 87.5%, suggesting that this treatment could be used particularly in rescue. Median survival time, without failure or relapse, was 15 months (Kaplan–Meier curve). Predictive factors (univariate analysis) of an initial and long‐term response were a small number of prior treatments received. However, at 2 yr, only seven patients had sustained response. Eight (23%) patients experienced adverse events: neuropathy for seven and bowel obstruction for one. Vincristine efficacy in ITP was confirmed, and it could be a good strategy for treating resistant ITP, especially in emergencies. In this era of new therapeutics, VCR deserves to remain on the list of ITP treatments because of its initial efficacy, safety and low cost.     

Raised expression of APRIL in Chinese patients with immune thrombocytopenia and its clinical implications

Background: Immune thrombocytopenia (ITP) is an immune-mediated disorder in which destruction of platelets is accelerated by anti-platelet autoimmune antibodies. B-cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL), essential factors for B cell survival are elevated in systemic autoimmune diseases and correlated with clinical findings. High expression of BAFF has been shown in patients with ITP, but the status of APRIL in ITP is still unknown.

Objective: To determine the expression of APRIL and it receptors, B-cell maturation antigen (BCMA) and trans-membrane activator and calcium modulator and cyclophilin ligand interactor (TACI), in patients with ITP, and evaluate the correlation between plasma APRIL levels and platelet accounts or other clinical parameters.

Methods: Plasma samples from 57 patients with ITP, and 30 normal healthy subjects were assayed for APRIL plasma concentration by enzyme linked immunosorbent assay. Real-time quantitative polymerase chain reaction was performed to determine the mRNA expression of APRIL and its receptors (BCMA and TACI) in peripheral blood mononuclear cells (PBMNCs) in 25 normal controls and 34 untreated ITP patients with active disease.

Results: The APRIL levels in the plasma samples from patients with ITP were significantly higher than those from healthy controls (p = 0.000). PBMNCs may be a source of the excess APRIL. Treated patients with normal platelet count have relatively normal plasma APRIL (p = 0.599). Plasma APRIL levels in active patients were significantly correlated with platelet counts (r = ? 0.387 and p = 0.024).

Conclusion: APRIL is over expressed in untreated active ITP patients and might be a pathogenic factor of this disorder.     

Piperacillin and vancomycin induced severe thrombocytopenia in a hospitalized patient

In hospitalized patients with complex medical problems on numerous drugs, thrombocytopenia may have a multiple confounding etiology. Keeping this in mind, it is of utmost importance to monitor the platelet count regularly during hospitalization and on subsequent follow-up visits, even after the most probable etiology has been identified/most likely causative drug has been withdrawn. Isolated thrombocytopenia with no evidence of microangiopathic hemolysis on the peripheral blood smear in an acutely ill hospitalized patient implicated sepsis, disseminated intravascular coagulation and drugs as the most probable causes. Our patient represents an uncommon case of antibiotic-induced severe immune thrombocytopenia, as he developed both vancomycin-dependent and piperacillin-dependent antibodies, while being treated for cellulitis (vancomycin-specific antibodies of the IgG isotype, and both IgG and IgM antibodies specific for piperacillin were identified in laboratory testing). Vancomycin was stopped before the reports were available. Following this, the patient's platelet count showed a transient upward trend, but then the thrombocytopenia worsened drastically reaching a nadir of 10,000/µL. The platelet count returned to normal only after piperacillin/tazobactam was stopped after a week, thus establishing it as the cause of the more severe thrombocytopenia, which occurred later on; this was subsequently confirmed by the laboratory results. Vancomycin is an established cause of drug-induced immune thrombocytopenias, especially in acutely ill, hospitalized or elderly patients, whereas incidents of piperacillin/tazobactam-induced immune thrombocytopenia are uncommon. In case clinical suspicion is high, workup should include immunoprecipitation and flow cytometry studies to confirm antiplatelet antibodies.     

Fondaparinux for intra and perioperative anticoagulation in patients with heparin-induced thrombocytopenia candidates for peripheral vascular surgery: Report of 4 cases

IntroductionIntra and perioperative anticoagulation in patients with heparin induced thrombocytopenia (HIT), candidates for peripheral vascular surgery remains a challenge, as the best alternative to heparin has not yet been established. We evaluated the off-label use of fondaparinux in four patients with HIT, undergoing peripheral vascular surgery procedures.Presentation of casesFour patients of whom 3 men of a mean age of 66 years, with proven heparin induced thrombocytopenia (HIT) underwent two axillo-femoral bypasses, one femoro-popliteal bypass and one resection of a splenic artery aneurysm under fondaparinux. No intra or perioperative bleeding or thrombosis of new onset was observed.DiscussionIn the absence of a valid alternative to heparin for intra and perioperative anticoagulation in HIT, several other anticoagulants can be used in an off-label setting. However, no general consensus exist on which should be the one of choice. In this small series fondaparinux appeared to be both safe and effective.ConclusionsThese preliminary results seem to justify the off-label use of fondaparinux for intra and perioperative anticoagulation in patients with HIT, candidates for peripheral vascular surgery interventions.     

Development of a high-yield expression and purification system for platelet factor 4

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction characterized by IgG antibodies bound to complexes of platelet factor 4 (PF4) and heparin. The majority of diagnostic tests for HIT rely on an exogenous source of PF4 to identify anti-PF4/heparin antibodies. These include the PF4-dependent enhanced serotonin release assay (PF4-SRA) among others. Using a bacterial expression system, we developed a novel and efficient method of producing recombinant human PF4 (rhPF4) that is biochemically and antigenically similar to platelet-derived human PF4. rhPF4 was produced using the pET expression system in the BL21(DE3) strain of Escherichia coli. The system was optimized for protein expression using isopropyl β-D-1-thiogalactopyranoside at different induction temperatures and incubation times. rhPF4 solubility was improved by using different detergents during cell lysis and by purifying with heparin affinity and ion exchange chromatography. Biochemical characteristics of rhPF4 were investigated using mass spectrometry, SDS-PAGE analysis, and gel filtration chromatography and compared to platelet-derived PF4. Antigenic and functional characteristics of rhPF4 were studied using the anti-PF4/heparin EIA and the PF4-SRA. Using this method, we could produce 11.4 ± 0.6 mg of pure rhPF4 per liter of bacterial culture. Absorbance readings from the anti-PF4/heparin EIA using platelet-derived and rhPF4 were highly correlated (n = 194; r = 0.9545, p < 0.0001); and functional release of serotonin in the PF4-SRA induced by anti-PF4/heparin antibodies was similar to either platelet-derived or rhPF4 and heparin (r = 0.9597, p < 0.0001). Our method of rhPF4 production is efficient and does not rely on a source of platelets. The rhPF4 purification method described produces greater yields at a lower cost than other current methods. The application of this method can improve the efficiency of biochemical investigations and HIT diagnostic testing by supplying sufficient amounts of PF4.