ADAMTS-13 level in children with severe diarrhea-associated hemolytic uremic syndrome: Unmasking new association.

Severe deficiency of ADAMTS-13 leads to thrombotic thrombocytopenic purpura. Few studies have reported reduced activity of ADAMTS-13 in patients with atypical and typical hemolytic uremic syndrome (HUS). We hypothesized that ADAMTS-13 deficiency might play a role in the pathogenesis of severe HUS. This study aimed to evaluate the ADAMTS-13 level in severe typical HUS. This prospective case-control study was carried out in the Pediatric Nephrology Unit and Clinical Pathology Department, Faculty of Medicine, Zagazig University from February 2013 to February 2014. The study included 15 consecutive children with typical HUS as well as 15 healthy children as a control group. Routine laboratory investigations were performed. Assessment of serum ADAMTS-13 level was performed using the Quantikine human ADAMTS-13 ELISA kit. Data were analyzed using Statistical Package for Social Sciences version 16. Nonparametric values were expressed as median and range, and the median of two groups was tested by Mann-Whitney test. The serum ADAMTS-13 level was significantly lower in HUS patients when compared to the control group (P < 0.05). There were significant negative correlations between ADAMTS-13 level and duration on dialysis, as well as serum urea and creatinine. Furthermore, there were significant positive correlations between serum ADAMTS-13 level and both hemoglobin level and platelet count. Our study suggests that the ADAMTS-13 level was decreased in children with severe typical HUS and its deficiency correlated with disease severity.

Carboxypeptidase B2 and N play different roles in regulation of activated complements C3a and C5a in mice.

Essentials Two basic carboxypeptidases are present in plasma, B2 (CPB2) and N (CPN). Cpb2-/- and Cpn-/- mice were challenged in a hemolytic uremic syndrome (HUS) model vs. wild type. Cpb2-/- exacerbates HUS while Cpn-/- exacerbates cobra venom factor challenge vs. wild type mice. CPB2 and CPN have overlapping but non-redundant roles. SUMMARY: Background There are two basic carboxypeptidases in plasma. Carboxypeptidase B2 (CPB2) is activated from a circulating zymogen, proCPB2, and carboxypeptidase N (CPN) is constitutively active with both inactivating complement C3a and C5a. Aims To test the roles of CPB2 and CPN in complement-driven mouse models of cobra venom factor (CVF) challenge and hemolytic-uremic syndrome (HUS). Methods Cpb2-/- , Cpn-/- and wild-type (WT) mice were compared in an HUS model induced by Shiga toxin and lipopolysaccharide administration and following CVF administration. Results HUS was exacerbated in Cpb2-/- mice more than in Cpn-/- mice, compared with WT mice. Cpb2-/- mice developed the HUS clinical triad of microangiopathic hemolytic anemia, uremia and thrombocytopenia. Treatment with anti-C5 antibody improved survival of both Cpb2-/- and Cpn-/- mice. In contrast, when challenged acutely with CVF, the reverse phenotype was observed. Cpn-/- mice had markedly worse disease than Cpb2-/- mice, whereas the WT mice were resistant. Conclusions CPN and CPB2 play overlapping but non-redundant roles in regulating complement activation in vivo. The constitutively active CPN is key for inactivation of systemic C5a, whereas CPB2 functions as an on-demand supplementary anaphylatoxin inhibitor in inactivating excessive C5a formed locally.

Diagnostic relevance of ADAMTS13 activity: evaluation of 28 patients with thrombotic thrombocytopenic purpura - hemolytic uremic syndrome clinical diagnosis.

INTRODUCTION: The significance of ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin motif-13) activity for diagnosis and therapy of thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) is still a controversial issue. OBJECTIVE: The aim of this report was to analyze the value of ADAMTS13 measurements in the diagnosis of TTP and HUS. METHODS: At presentation, we analyzed patients with idiopathic TTP (n = 18), secondary TTP (n = 4), diarrhea positive HUS (n = 3) and diarrhea negative HUS (n = 3) treated in Belgrade, Serbia from 2004 to 2010. ADAMTS13 activity from acute phase samples was measured using the residual collagen binding activity assay at the Haemophilia and Thrombosis Centre, Milan, Italy. RESULTS: There was a significant correlation between reduced ADAMTS13 activity and idiopathic TTP diagnosis (p = 0.000) as well as between lower ADAMTS13 activities and higher reticulocytes (p = 0.017) and lactate dehydrogenase levels (p = 0.027). Significant correlation was also found between higher protease activity and diagnosis of HUS (p = 0.000). There was a statistically significant correlation between higher ADAMTS13 activities and higher platelets count (p = 0.002), blood urea nitrogen (p = 0.000), and creatinine level (p = 0.000). CONCLUSION: Severe ADAMTS13 deficiency points at the diagnosis of idiopathic TTP and it is present in the secondary TTP but not in HUS.

Atypical hemolytic uremic syndrome and thrombotic thrombocytopenic purpura: clinically differentiating the thrombotic microangiopathies.

The increased understanding of the pathophysiology of both atypical hemolytic uremic syndrome (aHUS) and thrombotic thrombocytopenic purpura (TTP) in recent years has led to significant therapeutic advances for both conditions. These advances have placed an increased emphasis on a more rapid differentiation of both disorders which remain clinical diagnoses. In particular, recent data demonstrating the effectiveness of complement inhibition in patients with aHUS have increased the need for a more rapid and accurate differentiation of aHUS and TTP. Previously utilized criteria have used the presence or absence of neurologic or renal injury and the pretreatment ADAMTS13 activity to differentiate aHUS from TTP. The use of presenting clinical symptoms and findings alone to differentiate these conditions is problematic given their overlapping clinical presentations. Similarly, the use of the pretreatment ADAMTS13 activity alone to differentiate aHUS from TTP is also problematic, and could lead to the inappropriate witholding of plasma exchange (PEX) therapy. However, when used collectively, the pretreatment clinical findings (symptoms and laboratory data) and ADAMTS13 activity in the context of the patient's response to PEX therapy can allow for a more effective differentiation of these two disorders in a timely fashion that will allow for the prompt initiation of the most appropriate therapy.

Clinical experience in treatment of thrombotic thrombocytopenic purpura--hemolytic uremic syndrome with 28 patients.

BACKGROUND: Neither optimal treatment nor significance of ADAMTS13 (A Desintegrin And Metalloprotease with ThromboSpondin type 1 repeats) activity for diagnosis and therapy of thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome (HUS) have not been defined yet. The aim of the report is to analyze response to different volumes of plasma exchange (PE), and relationship to ADAMTS13. DESIGN AND METHODS: 28 patients clinically diagnosed with idiopathic TTP (n = 18), secondary TTP (n = 4), atypical HUS (n = 3) and typical HUS (n = 3) manifested 31 acute episodes. Patients were treated with PE in 26, and with plasma transfusion in 5 episodes with additional different therapies. RESULTS: PE volumes were as follows: 1 in 7, 1.5 in 3, 2 in 14, and intensifying schedule (1 to 1.5) in 2 episodes. Procedure number was lower in patients treated with 2 and 1.5 (p = 0.019) than in those treated with 1 volume exchange and PE intensifying, respectively (p = 0.010). PE response rate was 25/26 (96.15%). Exacerbation frequency was higher in idiopathic TTP patients (3/19) treated with 1 compared with patients treated with > 1 volume exchange (p = 0.003). Survival rate was 25/28 (89.29%). ADAMTS13 activity was reduced in 22 with severe deficiency in 14 patients. CONCLUSION: Patients responded to different treatments regardless of ADAMTS13 activity, requiring less PEs with larger volume exchanges.

Hemolytic uremic syndrome and rhabdomyolysis in a patient with succinate coenzyme Q reductase (complex II) deficiency.

Hemolytic uremic syndrome (HUS) is characterized by microangiopathic hemolytic anemia, thrombocytopenia and acute renal failure. Besides diarrhea-associated HUS, due to verotoxin-producing Escherichia coli, in children HUS without prodromal diarrhea may be associated with other infectious and autoimmune diseases, genetic defects of the complement-regulator alternative-pathway, and inborn errors of vitamin B12 metabolism. Rhabdomyolysis is the dissolution of skeletal muscle due to various causes, including inborn errors of metabolism. Recurrent rhabdomyolysis and HUS have been previously described in one patient with a genetic defect of oxidative phosphorylation. We report the case of a 2-year-old boy with recurrent HUS and rhabdomyolysis in whom a succinate coenzyme Q reductase (complex II) deficiency was diagnosed. We hypothesize that defects of oxidative phosphorylation could be another etiological factor in atypical HUS.

A glucosylceramide synthase inhibitor protects rats against the cytotoxic effects of shiga toxin 2.

Postdiarrhea hemolytic uremic syndrome is the most common cause of acute renal failure in children in Argentina. Renal damage has been strongly associated with Shiga toxin (Stx), which binds to the globotriaosylceramide (Gb3) receptor on the plasma membrane of target cells. The purpose of the study was to evaluate the in vivo effects of C-9, a potent inhibitor of glucosylceramide synthase and Gb3 synthesis, on kidney and colon in an experimental model of hemolytic uremic syndrome in rats. Rats were i.p. injected with supernatant from recombinant Escherichia coli expressing Stx2 (sStx2). A group of these rats were orally treated with C-9 during 6 d, from 2 d prior until 4 d after sStx2 injection. The injection of sStx2 caused renal damage as well as a loss of goblet cells in colonic mucosa. Oral treatment with C-9 significantly decreased rat mortality to 50% and reduced the extension of renal and intestinal injuries in the surviving rats. The C-9 also decreased Gb3 and glucosylceramide expression levels in rat kidneys. It is particularly interesting that an improvement was seen when C-9 was administered 2 d before challenge, which makes it potentially useful for prophylaxis.

Pregnancy-associated hemolytic uremic syndrome revisited in the era of complement gene mutations.

In contrast to pregnancy-associated thrombotic thrombocytopenic purpura, the pathogenesis and presentation of pregnancy-associated atypical hemolytic uremic syndrome (P-aHUS) remain ill-defined. We conducted a retrospective study to assess the presentation and outcomes of patients presenting with P-aHUS and the prevalence of alternative C3 convertase dysregulation. P-aHUS occurred in 21 of the 100 adult female patients with atypical HUS, with 79% presenting postpartum. We detected complement abnormalities in 18 of the 21 patients. The outcomes were poor: 62% reached ESRD by 1 month and 76% by last follow-up. The risk for P-aHUS was highest during a second pregnancy. Thirty-five women, 26 (74%) of whom had complement abnormalities, had at least one pregnancy before the onset of a non-pregnancy-related aHUS. Outcomes did not differ between patients with pregnancy-related and non-pregnancy-related aHUS. Mutations in the SCR19-20 domains of factor H were less frequent in P-aHUS patients compared with non-pregnancy-related aHUS. Pregnancies in female patients with complement abnormalities (n = 44) were complicated by fetal loss and preeclampsia in 4.8% and 7.7%, respectively. Better understanding of complement dysregulation in pregnancy complications is essential, especially to guide development of pharmacologic agents to modulate this system.

The TT genotype of the C677T polymorphism in the methylentetrahydrofolate reductase as a risk factor in thrombotic microangiopathies: results from a pilot study.

In this study, we assessed the potential role of the TT genotype of the gene of the methylenetetrahydrofolate reductase for the manifestation of thrombotic microangiopathies, enrolling 40 affected patients (mean age [+/- standard deviation] 35 +/- 11 years). As a result, the methylenetetrahydrofolate reductase 677TT genotype was more prevalent in patients with thrombotic microangiopathies compared with controls (adjusted odds ratio = 2.58, 95% confidence interval = 1.2-5.7, P = .018), particularly in those suffering from the hemolytic uremic syndrome. A hemolytic more severe clinical course of thrombotic microangiopathies in carriers of the methylenetetrahydrofolate reductase 677TT genotype was not observed. In summary, our findings suggest a significant influence of the methylenetetrahydrofolate reductase genotype on the manifestation of thrombotic microangiopathies. The 677 TT genotype of this polymorphism appears to be a risk factor for manifestation of these rare thrombotic disorders, possibly explained by endothelial activation and increased oxidative stress.

Lessons learned from the Oklahoma thrombotic thrombocytopenic purpura-hemolytic uremic syndrome registry.

The Oklahoma TTP-HUS Registry provides a complete community perspective of thrombotic thrombocytopenic purpura (TTP). This is possible because plasma exchange is the essential treatment for TTP and the Oklahoma Blood Institute provides all plasma exchange procedures for a region encompassing most of the State, including 58 of Oklahoma's 77 counties. The Registry is an inception cohort of consecutive patients for whom plasma exchange treatment was requested for a diagnosis of either TTP or hemolytic uremic syndrome (HUS). All 382 patients identified from January 1, 1989 to December 31, 2007 have consented to be enrolled. Complete follow-up is available for 380 of 382 patients. Patients are described both by clinical categories, related to their associated conditions and clinically apparent etiologies, and by the presence of severe ADAMTS13 deficiency. ADAMTS13 activity has been measured on 235 (93%) of 254 patients since 1995. Registry data have provided new perspectives on the definition and diagnoses of these syndromes as well as their outcomes. Long-term follow-up has documented that relapse is common among patients with ADAMTS13 deficiency but rarely occurs in patients without ADAMTS13 deficiency. Long-term follow-up has also documented persistent abnormalities of health-related quality-of-life and cognitive function. In addition to providing new perspectives on the natural history of these syndromes, The Oklahoma TTP-HUS Registry provides a support group for our patients, information about evaluation and management for community physicians, and a resource for research and educational programs.

[Haemolytic uremic syndrome and thrombotic thrombocytopenic purpura: classification based on molecular etiology and review of recent developments in diagnostics]. / A hemolitikus urémiás szindróma és a trombotikus thrombocytopeniás purpura molekuláris szemléletu klasszifikációja és diagnosztikájuknak aktuális kérdései.

Haemolytic uremic syndrome and thrombotic thrombocytopenic purpura are overlapping clinical entities based on historical classification. Recent developments in the unfolding of the pathomechanisms of these diseases resulted in the creation of a molecular etiology-based classification. Understanding of some causative relationships yielded detailed diagnostic approaches, novel therapeutic options and thorough prognostic assortment of the patients. Although haemolytic uremic syndrome and thrombotic thrombocytopenic purpura are rare diseases with poor prognosis, the precise molecular etiology-based diagnosis might properly direct the therapy of the affected patients. The current review focuses on the theoretical background and detailed description of the available diagnostic possibilities, and some practical information necessary for the interpretation of their results.

Compensatory renal growth protects mice against Shiga toxin 2-induced toxicity.

Uninephrectomy (Unx) is followed by the compensatory renal growth (CRG) of the remaining kidney. Previous evidence has shown that during CRG, renal tissue is resistant to a variety of pathologies. We tested the hypothesis that the functional changes that take place during CRG could attenuate Shiga toxin (Stx) toxicity in a mouse model of Stx2-induced hemolytic uremic syndrome (HUS). The participation of nitric oxide (NO) was analyzed. After CRG induction with Unx, mice were exposed to a lethal dose of Stx2, and the degree of renal damage and mortality was measured. Stx2 effects on the growth, renal blood flow (RBF) and NO synthase (NOS) intrarenal expression in the remaining kidney were then studied. The induction of CRG strongly prevented Stx2-mediated mortality and renal damage. Administration of the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) during CRG partially impaired the protection. Both Stx2 and L-NAME interfered with the hypertrophic and hyperplastic responses to Unx, as well as with the increase in RBF. In intact mice, Stx2 decreased renal perfusion, inhibited endothelial NOS basal expression and enhanced inducible NOS expression; all of these effects were attenuated by prior Unx. It is concluded that during CRG mice are highly protected against Stx2 toxicity and lethality. The protective capacity of CRG could be related to the enhancement of renal perfusion and preservation of eNOS renal expression, counterbalancing two major pathogenic mechanisms of Stx2.

Reduced nitric oxide bioavailability in a baboon model of Shiga toxin mediated hemolytic uremic syndrome (HUS).

BACKGROUND: Although there is agreement that post-diarrheal hemolytic uremic syndrome (D+ HUS) is caused by Shiga toxin (Stx)-producing E. coli, little is known about factors that mediate the host response to these toxins and potentially contribute to pathogenesis. Nitric oxide (NO) is a candidate mediator by virtue of its antiplatelet and renal vasodilatory properties. METHODS: We used a baboon model of HUS to measure plasma and urinary NO metabolites and expression of NO synthase (eNOS and iNOS) in renal tissue following the intravenous administration of Stx-1. RESULTS: Plasma concentrations through 60 hours of observation did not differ significantly from controls. Urinary values (indexed against urinary creatinine) tended, however, to rise during the initial 12 hours following administration of Stx-1. This was followed by a sustained reduction that coincided with the development of hemolytic anemia (schistocytosis) and other features of HUS. However, immunohistochemical staining for eNOS and iNOS in tissue obtained immediately after death at a median of 59 hours showed similar levels in control and Stx-treated animals, despite the presence of a florid thrombotic microangiopathy and tubular injury in the Stx-treated group. CONCLUSION: We propose that urinary NO metabolite reduction was due to NO inactivation subsequent to its avid binding to free hemoglobin released from lysed red blood cells, and that this contributed to the acute renal failure by facilitating vasoconstriction and platelet aggregation and adhesion within the renal microvasculature.

Is factor V Leiden a risk factor for thrombotic microangiopathies without severe ADAMTS 13 deficiency?

About 60% of patients diagnosed with acute thrombotic thrombocytopenic purpura (TTP) display a severe ADAMTS13 deficiency. Recently, Raife et al. concluded from a small case series, that factor V Leiden (FVL) might constitute a risk factor for acute thrombotic microangiopathy (TMA) without severe ADAMTS13 deficiency. Therefore, we determined ADAMTS13 activity and FVL carrier-ship in 256 consecutive patients presenting with various forms of acute TMA, including patients diagnosed with TTP or hemolytic-uremic syndrome (HUS). The overall prevalence of FVL was 8.2% (6.25% among patients diagnosed with TTP, and 9% among those with HUS) concordant with the FVL prevalence reported in Europe. FVL was present in 9.9% of patients with ADAMTS 13 activity < 10% and in 9.7% of those with normal ADAMTS13 activity (> 50%). We conclude that FVL is not more prevalent in TMA patients without as compared to those with severe ADAMTS13 deficiency. The prevalence of FVL carriers in certain HUS subgroups (HUS with ADAMTS 13 activity > 50%) reaching 12.3% suggests that a contributory role of FVL in the pathogenesis of defined forms of HUS needs further study.

Role of p38 MAP kinase pathway in a toxin-induced model of hemolytic uremic syndrome.

The role of proinflammatory cytokines in a rat model of toxin-induced hemolytic uremic syndrome (HUS) was studied. Male Sprague-Dawley rats underwent continuous saline infusion (6 ml/h) via a tail vein and received a bolus injection of saline (control), lipopolysaccharide (LPS, 10 microg/100 g body weight), ricin (6.7 microg/100 g body weight), or ricin with LPS (ricin+LPS). They were then observed for 8 h. Blood samples and kidney tissues were obtained at the end of the experiment. The effects of FR 167653, a potent inhibitor of interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) production, were also examined in ricin+LPS-treated rats. Only ricin+LPS-treated rats developed significant thrombocytopenia, hemolysis, and oliguric acute renal failure with extensive glomerular thrombotic microangiopathy, which was characterized by glomerular microthrombi and apoptosis of glomerular endothelial cells. Thrombotic microangiopathy was not detected in other organs, including the brain, liver, spleen, pancreas, lung, colon, and intestine. Significantly elevated levels of serum IL-1beta and TNF-alpha were detected only in ricin+LPS-treated rats. Treatment of ricin+LPS-treated rats with FR 167653 significantly reduced the serum levels of IL-1beta and TNF-alpha, accompanied by improvement of the oliguric renal failure and glomerular thrombotic microangiopathy. These findings indicate that the increased serum levels of IL-1beta and TNF-alpha, which probably result in the apoptosis of glomerular endothelial cells, play a pivotal role in the development of this rat model of toxin-induced HUS. The findings also suggest that inhibition of these proinflammatory cytokines may prevent the development of HUS.

Von Willebrand factor--cleaving protease activity in thrombotic microangiopathy after living donor liver transplantation: a case report.

Defective plasma activity of Von Willebrand factor (VWF)-cleaving protease (CP) and/or the inhibitors against this protease has been shown to have a pathological role in several forms of thrombotic microangiopathy (TMA). This report describes a patient for whom a diagnosis of TMA was made immediately after living donor liver transplantation. In this patient, activity of VWF-CP and its inhibitor were analyzed serially. At the onset of the disease, VWF-CP activity was quantified as 17%. Inhibitor against this protease was positive, with a titer of 0.6 Bethesda U/mL, and its inhibitory activity was quantified as 3.8 Bethesda U/mg immunoglobulin G. Laboratory parameters and clinical features were significantly improved after induction of plasma exchange (PE) with fresh frozen plasma and concurrent cessation of tacrolimus therapy. The inhibitors disappeared after one session of PE. However, VWF-CP activity after a transient increase and again decreased to subnormal levels after completion of PE. Nevertheless, this did not result in disease recurrence. In view of sustained VWF-CP activity at disease onset and the absence of definite correlations between levels of this protease and clinical features, abnormality of this enzyme system had no essential role in the pathogenesis of TMA in this case. Clinical findings suggest that TMA was tacrolimus-induced.

ADAMTS13 activity in thrombotic thrombocytopenic purpura-hemolytic uremic syndrome: relation to presenting features and clinical outcomes in a prospective cohort of 142 patients.

Initial management of patients with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) is difficult because of lack of specific diagnostic criteria, high mortality without plasma exchange treatment, and risks of plasma exchange. Although severe ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type 1 repeats) deficiency may be specific for TTP, the role of ADAMTS13 activity measurements for initial management decisions is unknown. ADAMTS13 was measured before beginning plasma exchange treatment in 142 (88%) of 161 consecutive patients with clinically diagnosed TTP-HUS with assignment to 1 of 4 categories: less than 5% (severe deficiency), 5% to 9%, 10% to 25%, and more than 25%. Eighteen (13%) of 142 patients had severe ADAMTS13 deficiency. Among 6 predefined clinical categories (stem cell transplantation, pregnant/postpartum, drug association, bloody diarrhea, additional/alternative disorder, idiopathic), severe deficiency occurred only among pregnant/postpartum (2 of 10) and idiopathic (16 of 48) patients. The presenting features and clinical outcomes of the 16 patients with idiopathic TTP-HUS who had severe ADAMTS13 deficiency were variable and not distinct from the 32 patients with idiopathic TTPHUS who did not have severe ADAMTS13 deficiency. Many patients in all ADAMTS13 activity categories apparently responded to plasma exchange treatment. Therefore, severe ADAMTS13 deficiency does not detect all patients who may be appropriately diagnosed with TTP-HUS and who may respond to plasma exchange treatment.