How I treat: the clinical differentiation and initial treatment of adult patients with atypical hemolytic uremic syndrome.

Published data demonstrating the efficacy of complement inhibition therapy in patients with atypical hemolytic uremic syndrome (aHUS) are remarkable in contrast to the historically poor long-term prognosis for aHUS patients treated with plasma-based therapy. Although both aHUS and acquired thrombotic thrombocytopenic purpura (TTP) remain clinical diagnoses, an increased understanding of both conditions has improved our ability to differentiate aHUS from acquired TTP. These same data have also demonstrated the importance of a more rapid identification and diagnosis of aHUS as the recovery of end-organ injury present appears to be related to the time to initiate therapy with eculizumab. The diagnosis of acquired TTP can be confirmed by the finding of severely deficient ADAMTS13 activity (<10%) with evidence of an ADAMTS13 antibody inhibitor whereas merely deficient ADAMTS13 activity in the absence of an ADAMTS13 autoantibody is more consistent with congenital TTP. In the absence of an objective diagnostic test, clinicians must rely collectively on platelet count, serum creatinine, and ADAMTS13 activity in the context of the response to plasma exchange therapy to identify patients whose diagnosis is most consistent with aHUS, and thus be more likely to benefit from therapy with eculizumab.

Thrombotic thrombocytopenic purpura: 2012 American Society for Apheresis (ASFA) consensus conference on classification, diagnosis, management, and future research.

The American Society for Apheresis (ASFA) conducted a 1 day consensus conference on Thrombotic Thrombocytopenic Purpura (TTP) during its annual meeting in Atlanta, GA, on April 10, 2012. The authors of this article, a subcommittee of ASFA's Clinical Applications Committee, developed several questions with regard to definitions, classification, pathophysiology, diagnosis, management, and future research in TTP. These questions were provided to the seven invited speakers who are the experts in the field of TTP. Two moderators conducted the proceedings of the conference which was attended by more than 100 participants. After each presentation, there was an open discussion that included moderator-selected written questions submitted by the audience. A medical writer-generated transcript of the proceedings as well as each presentation was made available to the authors. Each summary was reviewed and approved by the respective speaker before submission of this article. The subcommittee also developed seven key questions for blinded, electronic polling conducted by the moderators to generate a consensus amongst the speakers. This article includes these presentation summaries as well as results of the electronic poll.

TTP/HUS and prognosis: the syndrome and the disease(s).

Patients presenting with the syndrome of microangiopathic hemolysis and thrombocytopenia, without Shiga toxin-associated colitis, have thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS). Prognosis for TTP/HUS has changed over time from a fatal disorder associated with the classic pentad to a syndrome associated with 80% survival in the plasma exchange era. A growing number of mechanisms, including but not exclusive to severe ADAMTS13 deficiency, are now understood to result in this syndrome, and the prognosis of patients with TTP/HUS is related to many additional factors. This update on prognosis explores recent registry data studying both acquired idiopathic and also familial or recurrent forms of TTP/HUS, to delineate how mortality varies by underlying disease mechanism. This paper also explores the association between mortality and clinical presenting features, as well as whether the case is a primary or relapsed presentation. Recent data support an understanding of TTP/HUS as a heterogeneous syndrome with variable mortality, and with specific subgroups demonstrating an excellent outcome.

The thrombotic thrombocytopenic purpura and hemolytic uremic syndromes: overview of pathogenesis (Experience of The Oklahoma TTP-HUS Registry, 1989-2007).

The Oklahoma TTP (thrombotic thrombocytopenic purpura)-HUS (hemolytic uremic syndrome) Registry, an inception cohort of 382 consecutive patients with TTP-HUS, provides a complete community perspective of these syndromes. TTP is the diagnostic term used for all adults, with or without neurologic or renal abnormalities; it is typically an acquired disorder; it may rarely result from congenital ADAMTS13 deficiency. HUS is the term used for children who have renal failure, most often caused by Escherichia coli O157:H7 infection; it may rarely result from congenital abnormalities of complement regulation. Clinical categories related to associated conditions and potential etiologies provide a structure for describing pathogenesis of the acquired syndromes. (1) Following allogeneic hematopoietic stem cell transplantation; a disorder primarily affecting kidneys described as transplantation-associated thrombotic microangiopathy. (2) Pregnancy-associated; pregnancy is a prominent risk factor for the development of TTP. (3) Drug-associated; acute, immune-mediated systemic syndromes and also dose-dependent renal toxicity. (4) Bloody diarrhea prodrome, suggesting an enteric infectious etiology. (5) Presence of an additional autoimmune disorder. (6) Idiopathic. A severe deficiency of ADAMTS13 activity contributes to the pathogenesis of many idiopathic patients and also some patients who present during pregnancy, with bloody diarrhea, or who have additional autoimmune disorders.

The Oklahoma Thrombotic Thrombocytopenic Purpura-Hemolytic Uremic Syndrome Registry: the Swiss connection.

OBJECTIVES: Thrombotic thrombocytopenic purpura (TTP) was initially described as an uncommon and usually fatal disorder. With effective treatment it is more frequently diagnosed, the clinical presentations are more diverse, and long-term sequelae are becoming recognized. METHODS: Patient data are from The Oklahoma TTP-hemolytic uremic syndrome (HUS) Registry, an inception cohort of 348 consecutive patients with their first episode of clinically diagnosed TTP or HUS, 1989-2006. The Registry enrolls all patients in a defined region who are diagnosed with TTP or HUS and for whom plasma exchange treatment is requested. ADAMTS13 activity has been analyzed on 235 (93%) of 254 patients since 1995 at the University of Berne, Switzerland. Patients are described by clinical categories, related to their associated conditions and clinically apparent etiologies, and by the presence of severe ADAMTS13 deficiency. RESULTS AND CONCLUSIONS: The clinical spectrum of syndromes described as TTP is variable with multiple etiologies. Advances in clinical and laboratory investigation have provided better understanding of the pathogenesis of these syndromes, their clinical evaluation and management, and their long-term outcomes. In addition to new information about TTP, these studies provide a model for translational research to define the complete community spectrum of uncommon disorders.

[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.

Outcome of severe adult thrombotic microangiopathies in the intensive care unit.

OBJECTIVE: Thrombotic microangiopathies, namely thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, are uncommon microvascular occlusive diseases. Despite the dramatic improvement in the outcome by exogenous plasma supply, either through plasma infusion or through plasma exchange, patients frequently require support in the intensive care unit. In the present study, we evaluated the outcome of a large cohort of patients with severe thrombotic microangiopathies. DESIGN: A retrospective multicenter study from January 1998 to June 2001. SETTING: Fourteen French university hospital medical intensive care units. PATIENTS: Sixty three adult patients with severe thrombotic microangiopathies. MEASUREMENTS AND RESULTS: Of the 63 patients, 19 had a clinical presentation of thrombotic thrombocytopenic purpura, 18 had hemolytic uremic syndrome and 26 had combined neurologic and renal failures. Infections were the main etiology associated with thrombotic microangiopathies. The mortality rate was 35%. Of the survivors, all achieved complete remission. Whereas neurologic failure assessed through the Glasgow coma scale was an independent predictor of mortality [HR=0.845 (CI 95%: 0.759-0.940), P=0.002], renal impairment did not appear to be an adverse prognostic factor. The use of plasma exchange was independently associated with survival [HR=0.269 (CI 95%: 0.104-0.691), P=0.006]. CONCLUSIONS: Thrombotic microangiopathies with severe organ dysfunctions leading to hospitalization in the intensive care unit are associated with high mortality. Neurologic impairment appears to be the main adverse prognostic factor correlated to mortality, and the study confirms the importance of plasma exchange in the treatment of high-risk patients.

Thrombotic thrombocytopenic purpura and its look-alikes.

The thrombotic thrombocytopenic purpura syndrome (TTP) can be mistaken for a number of other conditions, and it is important to diagnose correctly and treat appropriately. We describe the features of TTP that can help make a positive diagnosis and other conditions in the differential diagnosis with symptoms that can overlap and mimic those of TTR. We discuss TTP and its variants, hemolytic uremic syndrome, disseminated intravascular coagulation, heparin-induced thrombocytopenia, antiphospholipid syndrome, Evans syndrome, preeclampsia/eclampsia, HELLP syndrome, acute fatty liver of pregnancy, and multiorgan failure.

Abnormalities of von Willebrand factor multimers in thrombotic thrombocytopenic purpura and the hemolytic-uremic syndrome.

PURPOSE: To analyze and review von Willebrand factor (vWF) multimeric patterns in patients with single-episode thrombotic thrombocytopenic purpura (TTP), intermittent TTP (episodes at infrequent, irregular intervals), chronic relapsing TTP (episodes at frequent, regular intervals), and the hemolytic-uremic syndrome (HUS). PATIENTS AND METHODS: Platelet-poor plasma samples were obtained in EDTA, citrate, or citrate-hirudin-aprotinin-leupeptin from 36 patients with single-episode TTP, eight patients with intermittent TTP, four patients with chronic relapsing TTP, and 26 patients with HUS. The samples were separated by sodium dodecyl sulfate-agarose gel electrophoresis, overlaid with rabbit 125I-anti-human vWF IgG, and analyzed by autoradiography. RESULTS: Abnormalities of vWF multimers were found in platelet-poor plasma samples from 31 of 36 found in platelet-poor plasma samples from 31 of 36 patients (86%) at the onset of and during their single TTP episode. vWF multimers larger than those in normal plasma, and similar to vWF forms observed within normal human endothelial cells (unusually large vWF multimers), were demonstrated in 31% of the patients; 19% had either unusually large vWF multimers or a relative decrease in the largest plasma vWF forms in different serial samples; 36% had a relative decrease in the largest plasma vWF forms. These results imply that endothelial cell injury or intense stimulation, along with the attachment of unusually large vWF multimers and the largest plasma vWF forms to platelets, occurred during the single TTP episodes in most patients. Patterns of vWF multimers were normal in 92% of patients with single-episode TTP studied after recovery. All eight patients with intermittent TTP and the four patients with chronic relapsing TTP had unusually large vWF multimers in their plasma between episodes, and these multimers decreased or disappeared during relapses. Of 26 children and adults with HUS, 14 had a relative decrease in the largest plasma vWF multimeric forms and one had unusually large vWF multimers during the episode (vWF multimeric abnormalities in 58% of the patients). CONCLUSION: It is probable that vWF was involved in the pathophysiology of TTP in most of these patients with the single-episode, intermittent, or chronic relapsing types of TTP, and in more than 50% of the patients with HUS.

Assay of von Willebrand factor (vWF)-cleaving protease based on decreased collagen binding affinity of degraded vWF: a tool for the diagnosis of thrombotic thrombocytopenic purpura (TTP)

Patients with thrombotic thrombocytopenic purpura (TTP) have a deficiency of von Willebrand factor (vWF)-cleaving protease, whereas patients with hemolytic-uremic syndrome (HUS) show normal activity of this protease. Present methods for assaying vWF-cleaving protease by immunoblotting are time-intensive and cumbersome. We therefore developed a new functional assay based on the preferential binding of high-molecular-weight forms of vWF to collagen. In this assay, the diluted plasma sample to be tested is added to normal human plasma in which protease activity had been abolished. The vWF present in the protease-depleted plasma is digested by the vWF-cleaving protease in the test plasma. The proteolytic degradation leads to low-molecular-weight forms of vWF, which show impaired binding to microtiter plates coated with human collagen type III. The collagen-bound vWF is quantified using a peroxidase-conjugated rabbit antibody against human vWF. The values of vWF-cleaving protease activity in tested plasma samples are read from a calibration curve achieved by incubating the vWF-substrate with dilutions of a normal human plasma pool (NHP). Testing of plasma from patients with TTP and HUS showed that the assay can be used to distinguish between these two syndromes. The presence of an inhibitor can be detected by carrying out the test after incubation of NHP with the patient plasma sample, thus enabling differentiation of patients with familial TTP from those with nonfamilial TTP.

Upshaw-Schulman syndrome revisited: a concept of congenital thrombotic thrombocytopenic purpura.

Upshaw-Schulman syndrome (USS) is a congenital bleeding disorder characterized by repeated episodes of thrombocytopenia and microangiopathic hemolytic anemia that respond to infusions of fresh frozen plasma. Inheritance of USS has been thought to be autosomal recessive, because 2 siblings in the same family are often affected but their parents are asymptomatic. Recently, chronic relapsing thrombotic thrombocytopenic purpura (CR-TTP), reported almost exclusively in adults, was shown to be caused by inherited or acquired deficiency in the activity of a plasma von Willebrand factor-cleaving protease (vWF-CPase). The pathogenesis of USS is unknown, and a relationship between CR-YEP and USS has not been reported. We studied 3 unrelated USS patients (ST, SY, and KI) who presented with severe indirect neonatal hyperbilirubinemia. All 3 patients had undetectable vWF-CPase activity, and the inhibitors to vWF-CPase were all negative. In their parents with no clinical symptoms, vWF-CPase activities as a percentage of control samples (mother/father) were 17/20 for ST, 60/45 for SY, and 36/5.6 for KI. Thus, USS and vWF-CPase activity appear to be coinherited as autosomal recessive traits. Transfusion of fresh frozen plasma in 2 patients (ST and SY) resulted in the expected maximal increment of approximately 7% to 8% in vWF-CPase activity at 1 to 4 hours, but the levels became less than 3% within 2 days. After this decrease, platelet counts increased, plateaued in the normal range at 10 to 12 days, and declined thereafter. Thus, the 2 to 3 weeks of therapeutic benefit from plasma infusions will be discussed in relation to the intravascular lifetime of vWF-CPase.

Deficient activity of von Willebrand factor-cleaving protease in patients with Upshaw-Schulman syndrome.

We identified unusually large von Willebrand factor (vWF) multimers caused by deficient activity of vWF-cleaving protease in 2 patients with Upshaw-Schulman syndrome. The autoantibodies that inhibited the protease activity were not detected in the plasma of either patient. Periodic fresh-frozen plasma transfusion was effective for management of the hemolysis and thrombocytopenia. We detected enriched enzyme activity in a particular plasma fraction, although molecular cloning of this specific protease is needed to determine a more detailed pathogenesis and to develop new therapeutic approaches.