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      Malignant hypertension with thrombotic microangiopathy and persistent acute kidney injury (AKI)

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          Abstract

          Two cases of malignant hypertension presenting with acute kidney injury, thrombocytopenia and hemolytic anemia are presented. In both patients a prolonged duration of renal replacement therapy was required. The plasma levels of ADAMTS13 enzyme were not helpful in delineating the precise pathogenesis in both cases, as the decrements were not severe. We discuss the clinic-pathologic correlation of the biopsy findings and persistence of AKI.

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          Thrombotic microangiopathy and associated renal disorders*

          Thrombotic microangiopathy (TMA) is a pathological process involving thrombocytopenia, microangiopathic haemolytic anaemia and microvascular occlusion. TMA is common to haemolytic uraemic syndrome (HUS) associated with shiga toxin or invasive pneumococcal infection, atypical HUS (aHUS), thrombotic thrombocytopenic purpura (TTP) and other disorders including malignant hypertension. HUS complicating infection with shiga toxin-producing Escherichia coli (STEC) is a significant cause of acute renal failure in children worldwide, occurring sporadically or in epidemics. Studies in aHUS have revealed genetic and acquired factors leading to dysregulation of the alternative complement pathway. TTP has been linked to reduced activity of the ADAMTS13 cleaving protease (typically with an autoantibody to ADAMTS13) with consequent disruption of von Willebrand factor multimer processing. However, the convergence of pathogenic pathways and clinical overlap create diagnostic uncertainty, especially at initial presentation. Furthermore, recent developments are challenging established management protocols. This review addresses the current understanding of molecular mechanisms underlying TMA, relating these to clinical presentation with an emphasis on renal manifestations. A diagnostic and therapeutic approach is presented, based on international guidelines, disease registries and published trials. Early treatment remains largely empirical, consisting of plasma replacement/exchange with the exception of childhood STEC-HUS or pneumococcal sepsis. Emerging therapies such as the complement C5 inhibitor eculizumab for aHUS and rituximab for TTP are discussed, as is renal transplantation for those patients who become dialysis-dependent as a result of aHUS.
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            Microangiopathic hemolysis and renal failure in malignant hypertension.

            Renal dysfunction is an important cause of morbidity and mortality in patients with malignant hypertension. Microangiopathic hemolysis (MAHA) related to malignant hypertension may cause renal insufficiency by obstruction of interlobular arteries. We hypothesized that the presence of MAHA is an important indicator of renal dysfunction and recovery in malignant hypertension. We retrospectively analyzed 97 patients admitted between April 1994 and April 2004 with malignant hypertension. MAHA was defined as a low platelet count ( 220 U/L) or presence of schistocytes. MAHA was present in 26 of 97 patients (27%). Serum creatinine levels at admission were significantly higher in those with than in those without MAHA: median serum creatinine 690 micromol/L (interquartile range [IQR] 394 to 1105) and 120 micromol/L (IQR 82 to 211), respectively (P<0.01). Macroalbuminuria was present in 88% with versus 41% without MAHA (P<0.01). Patients with MAHA were more often black (73%; P<0.01) and had higher systolic blood pressure (mean 242 mm Hg versus 225 mm Hg; P<0.01). Dialysis was needed in 15 patients with MAHA (58%) versus 2 patients (3%) without MAHA. In 6 patients with MAHA, dialysis could be stopped. Cox regression analysis showed that MAHA and systolic blood pressure were the most important indicators of renal improvement during follow-up, with a hazard ratio of 0.24 (95% confidence interval [CI], 0.08 to 0.75; P=0.01) and 1.02 per mm Hg increase in systolic blood pressure (95% CI, 1.01 to 1.05; P=0.01). In conclusion, MAHA is an important indicator of renal insufficiency and recovery in patients with malignant hypertension.
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              Thrombotic microangiopathy in malignant hypertension and hemolytic uremic syndrome (HUS)/ thrombotic thrombocytopenic purpura (TTP): can we differentiate one from the other?

              Patients with malignant hypertension sometimes exhibit microangiopathic hemolytic anemia/thrombocytopenia known as thrombotic microangiopathy (TMA). On the other hand, severe hypertension is sometimes associated with hemolytic uremic syndrome (HUS)/thrombotic thrombocytopenic purpura (TTP). Because the clinical features of the two entities overlap significantly, it is sometimes difficult to distinguish one from the other. However, such differentiation is indispensable, since early performance of plasmapheresis is critical in HUS/TTP. It has been suggested that severe thrombocytopenia is one of the most useful differential points in diagnosing HUS/TTP from malignant hypertension caused by other etiologies. Early performance of plasmapheresis can be justified in the presence of both TMA and thrombocytopenia. However, thrombocytopenia can be seen in the cases with malignant hypertension from etiologies other than HUS/TTP, and in these particular cases, plasmapheresis is useless and can be harmful. Recently, the plasma level of ADAMTS13 (a disintegrin and metalloprotease domain, with thrombospondin type 1 motif 13), which is a von Willebrand Factor cleaving protease, has been shown to be very low in familial or some of the sporadic cases of TTP, and a low level of ADAMTS13 is very specific to TTP. Some reports have shown that patients with a very low plasma level of ADAMTS13 respond very well to plasmapheresis. We recently experienced two cases with TMA. Although both of our patients had severe hypertension with TMA, different therapeutic strategies ameliorated their illness: symptomatic treatment was effective in case 1, which showed normal ADAMTS13 activity, whereas plasma infusion was necessary to save case 2, which showed low ADAMTS13 activity. Thus, patients with a low level of ADAMTS13 activity might respond well to plasmapheresis or plasma infusion. When presented with patients with severe hypertension and thrombotic microangiopathy, ADAMTS13 activity may prove to be a promising adjunctive tool in differentiating TTP from TMA due to other etiologies, but in the meantime, we should make the choice of whether or not to perform plasmapheresis based on the degree of thrombocytopenia.
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                Author and article information

                Journal
                Clin Kidney J
                Clin Kidney J
                ckj
                ndtplus
                Clinical Kidney Journal
                Oxford University Press
                2048-8505
                2048-8513
                December 2014
                13 November 2014
                13 November 2014
                : 7
                : 6
                : 586-589
                Affiliations
                [1 ]Department of Medicine, Meharry Medical College, Nashville, TN, USA
                [2 ]Section of Renal Diseases,Vanderbilt University School of Medicine, Nashville, TN, USA
                [3 ]Renal Pathology division, Vanderbilt University School of Medicine, Nashville, TN, USA
                [4 ]Division of Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
                Author notes
                Correspondence and offprint requests to: Chike Nzerue; E-mail: cnzerue@ 123456mmc.edu
                Article
                sfu116
                10.1093/ckj/sfu116
                4240409
                8d44137d-defe-4a1c-a1aa-948bc2b8b062
                © The Author 2014. Published by Oxford University Press on behalf of ERA-EDTA.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

                History
                : 6 October 2014
                : 9 October 2014
                Categories
                Original Contributions
                Exceptional Cases

                Nephrology
                irreversible,malignant hypertension,thrombotic microangiopathy
                Nephrology
                irreversible, malignant hypertension, thrombotic microangiopathy

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