Guidelines on the diagnosis and management of the thrombotic microangiopathic haemolytic anaemias

Hemolytic uremic syndrome due to homozygous factor H deficiency

The majority of complement factor H mutations associated with atypical hemolytic uremic syndrome (HUS) are heterozygous. Homozygous mutations causing atypical hemolytic uremic syndrome are rare. We report a 7-month-old boy with HUS, severe hypocomplementemia (low C3 and normal C4 levels), and extremely low circulating levels of factor H. Genetic analysis showed homozygous 4 bp deletion in the gene encoding factor H in the patient, with his parents being carriers. The patient showed progression to end-stage renal disease and is presently on chronic ambulatory peritoneal dialysis.

Imitators of severe pre-eclampsia

There are many obstetric, medial, and surgical disorders that share many of the clinical and laboratory findings of patients with severe pre-eclampsia-eclampsia. Imitators of severe pre-eclampsia-eclampsia are life-threatening emergencies that can develop during pregnancy or in the postpartum period. These conditions are associated with high maternal and perinatal mortalities and morbidities, and survivors may face long-term sequelae. The pathophysiologic abnormalities in many of these disorders include vasospasm, platelet activation or destruction, microvascular thrombosis, endothelial cell dysfunction, and reduced tissue perfusion. Some of these disorders include acute fatty liver of pregnancy, thrombotic thrombocytopenic purpura, hemolytic uremic syndrome, acute exacerbation of systemic lupus erythematosus, and disseminated herpes simplex and sepsis syndromes. Differential diagnosis may be difficult due to the overlap of several clinical and laboratory findings of these syndrome. It is important that the clinician make the accurate diagnosis when possible because the management and complications from these syndromes may be different. Because of the rarity of these conditions during pregnancy and postpartum, the available literature includes only case reports and case series describing these syndromes. This review focuses on diagnosis, management, and counseling of women who develop these syndromes based on results of recent studies and my own clinical experience.

Thrombotic thrombocytopenic purpura: the masquerader

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder with a mortality rate of up to 90% if left untreated, and is characterized by microvascular thrombi, mainly in small arteries and capillaries, thrombocytopenia, hemolysis, and neurological abnormalities. Malignant hypertension (HTN) is a clinical syndrome characterized by severe hypertension associated with end-organ damage; including encephalopathy, renal dysfunction, and retinal hemorrhage due to platelet aggregation in the microcirculation leading to thrombotic microangiopathy (TMA). These are similar to TTP. Malignant hypertension can cause endothelial injury and fibrinoid necrosis in the vessel wall which results in its clinical manifestations. Therefore, it is difficult to differentiate malignant hypertension from TTP. However, it is critical to differentiate these two entities, as early initiation of plasmapheresis in TTP can be life saving. TTP is considered a masquerader as it can present with few clinical features and, if the index of suspicion is not very high, lead to mortality.

Refractory thrombotic thrombocytopenic purpura associated with oral contraceptives and factor V Leiden: a case report

Introduction

Thrombotic microangiopathies constitute a heterogeneous group of diseases characterised by microangiopathic haemolytic anaemia and thrombocytopaenia associated with platelet aggregation in the microcirculation responsible for ischaemic manifestations. Classically, thrombotic microangiopathies are described as encompassing two main syndromes: thrombotic thrombocytopaenic purpura and the haemolytic-uraemic syndrome Many cases of idiopathic thrombotic thrombocytopaenic purpura have, to date, been associated with severe ADAMTS13 metalloprotease deficiency while haemolytic uraemic syndrome usually occurs in the context of normal protease activity. Oestrogens and factor V Leiden have rarely been implicated in the pathogenesis of thrombotic microangiopathy.

Case presentation

We describe the case of a 17-year-old female with refractory thrombotic thrombocytopaenic purpura. The patient was receiving a new generation of oral contraceptives for dysmenorrhoea and had factor V Leiden. After undergoing prolonged and intense plasma exchange therapy for 40 days and high dose oral corticosteroids therapy for 90 days, our patient recovered fully.

Conclusion

Patients with refractory thrombotic thrombocytopaenic purpura should likely be evaluated for congenital thrombophilic disorders and for ingestion of drugs that have been associated with this rare form of thrombotic microangiopathy. Identification of these and as yet other unknown genetic and/or acquired risk factors may lead to more judicious treatment approaches.

[Acute renal failure secondary to hemolytic uremic syndrome in a pregnant woman with pre-eclampsia]

Acute renal failure is a serious complication of pregnancy associated with a high rate of morbidity and mortality; the incidence is currently 1 per 10,000 pregnancies. The most common causes are gestational hypertension, bleeding, sepsis, and intrinsic renal disease. Other less common pregnancy-related syndromes, such as HELLP syndrome or thrombotic microangiopathy, may also lead to kidney failure. Hemolytic uremic syndrome and thrombotic thrombocytopenic purpura are forms of thrombotic microangiopathy and although neither is specific to pregnancy, the incidence of these entities rises during gestation. The classic symptoms are fever, hemolytic microangiopathic anemia, thrombopenia, neurologic dysfunction, and kidney abnormalities. When renal involvement is the predominant manifestation, the diagnosis is usually hemolytic uremic syndrome.

Cardiac involvement in acute thrombotic thrombocytopenic purpura: association with troponin T and IgG antibodies to ADAMTS 13

INTRODUCTION

Evidence for cardiac involvement in thrombotic thrombocytopenic purpura (TTP) is uncommonly described.

METHODOLOGY

We retrospectively reviewed 41 patients assessing troponin T as a marker for cardiac involvement in acute TTP with clinical symptoms, electrocardiograms (ECG) and echocardiograms. A histopathological review of five patients who died of acute TTP was also undertaken.

RESULTS

In 54% (22/41) of patients, troponin T was >or=0.05microg L(-1) (normal range 0-0.01 microg L(-1)). Half (12/22) had cardiac symptoms and 8/22 with a raised troponin T reported chest pain. ECG changes were present in 62% of patients with a raised troponin T. Median anti-ADAMTS 13 IgG antibody was significantly higher (P=0.018) in patients with troponin T>or=0.05 microg L(-1) (58.5% (range 17-162%), compared with patients with troponin T<0.05 microg L(-1) (35%, range 9-134%). Patients who died had higher troponin T levels (median 0.305 microg L(-1)) and raised anti-ADAMTS 13 IgG (median 66.5%). On admission, there were no deaths in those with troponin T

CONCLUSION

Clinical symptoms, ECG changes and echocardiograms are poor predictors of cardiac disease in acute TTP. Troponin T is specific for cardiac muscle and a sensitive marker of myocardial damage. In TTP patients, raised levels (>or=0.05 microg L(-1)) signify myocardial necrosis associated with microvascular thrombi. Mortality and acute morbidity was associated with higher admission troponin T and raised IgG antibody (>67%) to ADAMTS 13.

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Key Words Collapse

MESH Headings

• ADAM Proteins/immunology
• ADAMTS13 Protein
• Acute Disease
• Autoantibodies/blood
• Biomarkers/blood
• Heart Diseases/diagnosis
• Heart Diseases/mortality
• Humans
• Immunoglobulin G
• Morbidity
• Mortality
• Purpura, Thrombotic Thrombocytopenic/complications
• Purpura, Thrombotic Thrombocytopenic/epidemiology
• Purpura, Thrombotic Thrombocytopenic/mortality
• Retrospective Studies
• Troponin T/blood

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Grants Collapse

Affiliation(s)

C Hughes Department of Haematology, University College London Hospitals, London, UK
J R McEwan
I Longair
S Hughes
H Cohen
S Machin
M Scully

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Guideline for the investigation and initial therapy of diarrhea-negative hemolytic uremic syndrome

This guideline for the investigation and initial treatment of atypical hemolytic uremic syndrome (HUS) is intended to offer an approach based on opinion, as evidence is lacking. It builds on the current ability to identify the etiology of specific diagnostic sub-groups of HUS. HUS in children is mostly due to infection, enterohemorrhagic Escherichia coli (EHEC), Shigella dysenteriae type 1 in some geographic regions, and invasive Streptococcus pneumoniae. These sub-groups are relatively straightforward to diagnose. Their management, which is outside the remit of this guideline, is related to control of infection where that is necessary and supportive measures for the anemia and acute renal failure. A thorough investigation of the remainder of childhood HUS cases, commonly referred to as "atypical" HUS, will reveal a risk factor for the syndrome in approximately 60% of cases. Disorders of complement regulation are, numerically, the most important. The outcome for children with atypical HUS is poor, and, because of the rarity of these disorders, clinical experience is scanty. Some cases of complement dysfunction appear to respond to plasma therapy. The therapeutic part of this guideline is the consensus of the contributing authors and is based on limited information from uncontrolled studies. The guideline proposes urgent and empirical plasmapheresis replacement with whole plasma fraction for the first month after diagnosis. This should only be undertaken in specialized pediatric nephrology centers where appropriate medical and nursing skills are available. The guideline includes defined terminology and audit points so that the early clinical effectiveness of the strategy can be evaluated.

A Canadian phase II study evaluating the efficacy of rituximab in the management of patients with relapsed/refractory thrombotic thrombocytopenic purpura

Rituximab is a chimeric monoclonal antibody that targets the human CD-20 antigen present on malignant and normal B lymphocytes. Recent clinical studies have shown a significant response rate when this drug is given to selected patients with thrombotic thrombocytopenic purpura (TTP). Given that the clinical manifestations of TTP may be the direct result of an auto-antibody against a regulatory Von Willebrand factor enzyme (ADAMTS13), it makes biological sense to consider a therapy that has the ability to diminish or eradicate antibody-producing B cells. Despite initial positive results, there is a need to identify which patients derive durable benefit from this agent. As in other conditions that utilize therapeutic immunosuppression, there is a risk that the addition of rituximab may also lead to serious opportunistic infections.

A comparison of thrombotic thrombocytopenic purpura in an inception cohort of patients with and without systemic lupus erythematosus

OBJECTIVES

To compare the clinical presentation, response to therapy and outcome of thrombotic thrombocytopenic purpura (TTP) in an inception cohort of patients with and without SLE.

METHODS

Medical records of patients diagnosed with TTP at Singapore General Hospital between January 2003 and December 2007 were reviewed.

RESULTS

Ten idiopathic TTP (iTTP) and eight SLE-associated TTP (sTTP) patients were identified, with iTTP patients being older (mean 50.4 vs 34.5 yrs). Five iTTP patients were ANA positive but did not have any features of SLE. All sTTP patients had active SLE at TTP diagnosis and had more renal involvement than iTTP (87.5% vs 50%). The mean duration from the first symptom suggestive of TTP to diagnosis was 7.7 days and 19.5 days in iTTP and sTTP patients. All patients received high-dose corticosteroids. Cytotoxic and immunosuppressive drugs were used more commonly (87.5% vs 50%) and earlier (Day 2/3 vs after Day 7) in sTTP patients. Vincristine was the drug of choice in iTTP and cyclophosphamide in sTTP. Three SLE patients received rituximab. Mortality for iTTP and sTTP was 50% (95% CI 19%, 81%) and 62.5% (95% CI 29%, 96%), respectively. The mean (s.d.) time to complete remission was 31.3 (+/- 26.4) days in sTTP (n = 3) and 16.8 (+/- 6.1) days in iTTP (n = 5).

CONCLUSION

Despite early and more aggressive therapy in sTTP, mortality was higher and the time to complete remission were longer, suggesting that sTTP is more severe. The tempo of development of TTP in SLE patients was slower.

Clinical outcomes after platelet transfusions in patients with thrombotic thrombocytopenic purpura

BACKGROUND

Reports of deterioration and death after platelet (PLT) transfusions in patients with thrombotic thrombocytopenic purpura (TTP) have led to recommendations that they should not be given except for life-threatening hemorrhage.

STUDY DESIGN AND METHODS

Published reports of PLT transfusions in patients with TTP were systematically reviewed and data from the Oklahoma TTP-HUS Registry, an inception cohort of 382 consecutive patients, 1989 through 2007, were analyzed.

RESULTS

A systematic review identified 34 publications describing outcomes of patients with TTP after PLT transfusions: 9 articles attributed complications to PLT transfusions, 4 suggested that they may be safe, and 21 articles did not comment about a relation between PLT transfusions and outcomes. Fifty-four consecutive patients from the Oklahoma TTP-HUS Registry were prospectively analyzed. ADAMTS13 activity was less than 10 percent in 47 patients; also included were 7 patients whose activity was not measured but who may have been deficient. Thirty-three (61%) patients received PLT transfusions. The frequency of death was not different between the two groups (p = 0.971): 8 (24%) patients who received PLT transfusions died (thrombosis, 5; hemorrhage, 1; sepsis, 2) and 5 (24%) patients who did not receive PLT transfusions died (thrombosis, 4; hemorrhage, 1). The frequency of severe neurologic events was also not different (p = 0.190): 17 (52%) patients who received PLT transfusions (in 5 of these 17 patients, neurologic events only occurred before PLT transfusions) and 7 (33%) patients who did not receive PLT transfusions.

CONCLUSION

Evidence for harm from PLT transfusions in patients with TTP is uncertain.

Interventions for haemolytic uraemic syndrome and thrombotic thrombocytopenic purpura

BACKGROUND

Haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are related conditions with similar clinical features of variable severity. Survival of patients with HUS and TTP has improved greatly over the past two decades with improved supportive care for patients with HUS and by the use of plasma exchange (PE) with fresh frozen plasma (FFP) for patients with TTP. Separate pathogenesis of these two disorders has become more evident, but management overlaps.

OBJECTIVES

To evaluate the benefits and harms of different interventions for HUS and TTP separately, in patients of all ages.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), conference proceedings, reference lists of articles and text books and contact with investigators were used to identify relevant studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) evaluating any interventions for HUS or TTP in patients of all ages.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data and evaluated study reporting quality using standard Cochrane criteria. Analysis was undertaken using a random effects model and results expressed as risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

For TTP, we found six RCTs (331 participants) evaluating PE with FFP as the control. Interventions tested included antiplatelet therapy (APT) plus PE with FFP, FFP transfusion and PE with cryosupernatant plasma (CSP). Two studies compared plasma infusion (PI) to PE with FFP and showed a significant increase in failure of remission at two weeks (RR 1.48, 95% 1.12 to 1.96) and all-cause mortality (RR 1.91, 95% 1.09 to 3.33) in the PI group. Seven RCTs were undertaken in children with HUS. None of the assessed interventions used (FFP transfusion, heparin with or without urokinase or dipyridamole, shiga toxin binding protein and steroids) were superior to supportive therapy alone, for all-cause mortality, neurological/extrarenal events, renal biopsy changes, proteinuria or hypertension at the last follow-up visit. Bleeding was significantly higher in those receiving anticoagulation therapy compared to supportive therapy alone (RR 25.89, 95% CI 3.67 to 182.83).

AUTHORS' CONCLUSIONS

PE with FFP is still the most effective treatment available for TTP. For patients with HUS, supportive therapy including dialysis is still the most effective treatment. All studies in HUS have been conducted in the diarrhoeal form of the disease. There were no RCTs evaluating the effectiveness of any interventions on patients with atypical HUS who have a more chronic and relapsing course.

The Role Of von Willebrand Factor In Hemorrhagic And Thrombotic Disorders

von Willebrand factor (VWF) is a multimeric plasma protein that mediates platelet adhesion as well as platelet aggregation at sites of vascular injury and acts as a carrier of factor VIII. Although acquired or inherited VWF deficiency is associated with a bleeding tendency, there is increasing evidence that VWF has a pivotal role in thrombogenesis. In fact, while the presence in the plasma of unusually large VWF multimers, due to a congenital or acquired deficiency of a VWF-cleaving metalloprotease, has been implicated in the pathogenesis of thrombotic thrombocytopenic purpura, high plasma levels of VWF have been associated with an increased risk of both arterial and venous thrombosis. The role of VWF in normal and pathological hemostasis is discussed in this review, and important advances in the pathophysiology, diagnosis, and treatment of VWF-associated disorders are also described.

Thrombotic thrombocytopenic purpura in 166 pregnancies: 1955-2006

A review of pregnancy-associated thrombotic thrombocytopenic purpura (TTP) in 166 pregnancies was undertaken using 92 English-language publications from 1955 to 2006. Initial and recurrent TTP presents most often in the second trimester (55.5%) after 1-2 days of signs/symptoms; postpartum TTP usually occurs following term delivery. TTP with preeclampsia (n = 28) exhibits 2-4 times higher aspartate aminotransferase (AST) values and lower total lactate dehydrogenase (LDH) to AST ratios (LDH to AST ratio = 13:1), compared with TTP without preeclampsia (LDH to AST ratio = 29:1). Maternal mortality is higher with initial TTP (26% vs 10.7%), especially with concurrent preeclampsia (44.4% vs 21.8%, P < .02). Although maternal mortality with TTP has substantially declined when plasma therapy is utilized, delay of diagnosis and therapy for initial TTP confounded by preeclampsia/hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome remains a significant maternal-perinatal threat. Rapid and readily available laboratory testing to quickly diagnose TTP and HELLP syndrome/preeclampsia is desperately needed to improve care.

Regional UK TTP registry: correlation with laboratory ADAMTS 13 analysis and clinical features

Thrombotic thrombocytopenic purpura (TTP) is an acute, rare, life-threatening disorder. This report presents the South East (SE) England registry for TTP, from April 2002 to December 2006, which included 176 patients and 236 acute episodes; 75% of patients were female and 25% were male, overall median age at presentation was 42 years. Mortality was 8.5%, most cases died before treatment was instigated. The main ethnic groups were Caucasian (64%) and Afro Caribbean (27%). Seventy-seven percent of cases were idiopathic, 5% were congenital and the remaining cases had a defined precipitant. Neurological features were the most prevalent, but cardiac involvement accounted for 42% of presenting features. The overall median number of plasma exchanges (PEXs) to remission was 15; between April 2002 and December 2003, the median number of PEXs was 19 and it was 12 between January 2004 and December 2006 (P < 0.0001). In the latter period, adjuvant therapies were reduced, but Rituximab was increased. ADAMTS 13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity was <10% in 74% and 95% of these cases had positive IgG antibodies to ADAMTS 13. Renal impairment and delayed normalisation of platelet count were the main differences between idiopathic and secondary TTP.

Abbreviated dose rituximab for immune-mediated hematological disorders

As rituximab, a monoclonal antibody targeting CD20, depletes B cells, there is considerable interest in its use in immune-mediated disorders. The majority of studies employ a four-dose regimen based on practice in lymphoma therapy. We describe our experience with one or two doses of 375 mg/m(2) of rituximab in 12 patients with relapsed and refractory immune-mediated hematological disorders. Eleven patients (92%) achieved a complete remission that has been sustained in 7 for a median of 14.5 (10.5-22) months. Four patients (36%) relapsed after responses of 1-18.5 months. This preliminary experience suggests that one or two doses of rituximab may have response and relapse rates comparable to multidose regimens while potentially providing considerable cost savings. Further prospective studies are planned.

Cyclosporin and plasma exchange in thrombotic thrombocytopenic purpura: long-term follow-up with serial analysis of ADAMTS13 activity

We hypothesized that cyclosporin (CSA) as adjunct to plasma exchange (PE) improves the efficacy of PE in idiopathic thrombotic thrombocytopenic purpura (TTP) via suppression of the antibody inhibitor of ADAMTS13. Our preliminary findings with CSA and PE as the upfront treatment of TTP suggested that the addition of CSA to PE significantly decreased the exacerbation (disease recurrence within 30 d of the last PE) rates compared to a cohort that received corticosteroids and PE as their upfront therapy of TTP. We present an updated analysis with long-term follow-up of 18 patients with idiopathic TTP treated with concurrent CSA and PE with analysis of serial measurements of ADAMTS13 activity, antigen and inhibitor concentration in the context of clinical outcome data. Overall, 16/18 (89%) patients achieved remission, similar to historical remission rates in idiopathic TTP with PE with only one patient suffering an exacerbation. Clinical responses correlated with improvements in ADAMTS13 activity and suppression of the antibody inhibitor of ADAMTS13. These data suggest that the efficacy of CSA is at least in part related to its suppression of the antibody inhibitor of ADAMTS13 and a subsequent improvement in ADAMTS13 activity and antigen.

Prevalence of the ADAMTS-13 missense mutation R1060W in late onset adult thrombotic thrombocytopenic purpura

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is most commonly associated with deficiency or inhibition of von Willebrand factor-cleaving protease (ADAMTS-13) activity. ADAMTS-13 mutations and polymorphisms have been reported in childhood congenital TTP, but their significance in adult onset TTP remains unclear.

OBJECTIVES

We sought to identify common ADAMTS-13 mutations in adults with late onset TTP and to investigate whether they may predispose acute clinical episodes of the disorder in adulthood.

PATIENTS/METHODS/RESULTS

We detected a missense mutation (C3178T) in exon 24 of ADAMTS-13 in 6/53 (11.3%) adult onset TTP patients, but no normal controls (n = 100). Three of the patients had pregnancy-associated TTP; three had chronic relapsing acute idiopathic TTP. C3178T encodes an arginine to tryptophan (R1060W) substitution in the TSP1-7 domain of ADAMTS-13. In vitro expression of mutant and wild-type ADAMTS-13 demonstrated that R1060W caused severe intracellular retention of ADAMTS-13 (<5% secretion) without affecting its metalloprotease activity. One homozygous and five heterozygous patients were identified. No other causative mutations were discovered, yet all six patients had ADAMTS-13 activity levels <5% at presentation (normal: 66-126%). Antibodies/inhibitors to ADAMTS-13 were detected in three/five heterozygous patients, and all six patients had subnormal antigen levels. Six asymptomatic first-degree relatives, including those of two probands with antibodies, were also heterozygous for C3178T; all but one had subnormal ADAMTS-13 activity.

CONCLUSION

The high prevalence of R1060W ADAMTS-13 in adult onset TTP, together with its absence in childhood congenital TTP cases reported elsewhere, suggests it may be a factor in the development of late onset TTP.

Cryosupernatant and solvent detergent fresh-frozen plasma (Octaplas) usage at a single centre in acute thrombotic thrombocytopenic purpura

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is an acute, life-threatening disorder and plasma exchange (PEX) remains the mainstay of treatment.

METHODS

We reviewed 50 acute TTP episodes to establish the efficacy and safety of cryosupernatant (CPP) and Octaplas.

RESULTS

Twelve episodes used CPP only and 15 episodes started with CPP and changed to Octaplas. Once Octaplas had been used, it was continued on further admissions. Cryosupernatant was used exclusively in 24% and Octaplas exclusively in 42% of all episodes. The number of citrate reactions and allergic (plasma) reactions were halved in those receiving only Octaplas compared with cryosupernatant. There were 22 line infections and in approximately 70% of cases the infection was associated with a reduction in platelet count. In all 50 episodes, the only documented thrombosis was a superficial non-central vein. In episodes receiving only cryosupernatant or Octaplas, there was no significant difference in the median number of PEX to remission, 7.0 (interquartile range, IQR 5-8.8) and 8.0 (IQR 6.5-22), respectively. Baseline viral screen in all episodes was negative after discharge following an acute episode.

CONCLUSION

There was no difference in number of PEX to remission with cryosupernatant and solvent/detergent fresh-frozen plasma (Octaplas). However, allergic/urticarial and citrate reactions were more common with cryosupernatant. There was no documented viral transmission with either product.

Twice-daily plasma exchange for patients with refractory thrombotic thrombocytopenic purpura: the experience of the Oklahoma Registry, 1989 through 2006

BACKGROUND

Twice-daily plasma exchange has been used for patients with thrombotic thrombocytopenic purpura (TTP) who are unresponsive to treatment with daily plasma exchange for many years but with no clear evidence of effectiveness.

STUDY DESIGN AND METHODS

The 18 years' experience of The Oklahoma TTP-HUS (hemolytic-uremic syndrome) Registry, 1989 through 2006, with twice-daily plasma exchange for 31 episodes of TTP in 28 patients is reported. A definite response to twice-daily plasma exchange was defined a priori as a platelet (PLT) count increase after twice-daily plasma exchange on two separate occasions during the treatment of a single episode of TTP, with no change of other treatments. A possible response was defined as a PLT count increase after initiation of twice-daily plasma exchange only once with or without change of other treatments.

RESULTS

A definite response to twice-daily plasma exchange occurred in 3 episodes (three patients), 27 episodes had a possible response, and 1 episode had no response. The three patients with a definite response had ADAMTS13 activities of 5, 6, and 12 percent and all had an inhibitor; the patient with no response was subsequently determined to have Rocky Mountain spotted fever.

CONCLUSION

Twice-daily plasma exchange was typically considered in acutely ill patients who had initially responded but then severe thrombocytopenia recurred, often with new neurologic abnormalities, while continuing daily plasma exchange. In three patients, twice-daily plasma exchange appeared to be beneficial. In most patients, a benefit of twice-daily plasma exchange could not be clearly documented because other treatments were initiated or intensified.

Thrombotic thrombocytopenic purpura in childhood: an uncommon but life-threatening cause of thrombocytopenia

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder characterised by microangiopathic haemolytic anaemia, thrombocytopenia and signs of ischaemic organ dysfunction such as neurological or renal impairment and fever. The diagnosis of TTP should be considered in any child presenting with thrombocytopenia, in particular those children with microangiopathic haemolysis, atypical immune thrombocytopenia purpura or Evan's syndrome. Distinguishing TTP from haemolytic uraemic syndrome is difficult, but where there is doubt about the diagnosis, a presumptive diagnosis of TTP should be made to allow potentially life-saving therapy with therapeutic plasma exchange. Recent advances in the molecular basis of the disease have resulted in assays for ADAMTS-13 activity, inhibitor levels and ADAMTS-13 mutation analysis. These assays help to distinguish TTP from haemolytic uraemic syndrome. However, the performance characteristics of these assays in the diagnosis and management of TTP are yet to be defined.

Thrombotic thrombocytopenic purpura: a thrombotic disorder caused by ADAMTS13 deficiency

A serious disorder with characteristic microvascular thrombosis involving the brain and other organs, thrombotic thrombocytopenic purpura (TTP) typically presents with thrombocytopenia, hemolysis with schistocytes on blood smears, and mental changes or seizures. It may progress rapidly to a fatal end if the patient is not treated immediately with plasma. Recent advances have shown that TTP is caused by deficiency of a circulating, von Willebrand factor cleaving metalloprotease, ADAMTS13. This new knowledge will provide clues to improve the diagnosis and management of this intriguing disease.

Pathogenesis and prognosis of thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is a clinicopathological syndrome characterized by thrombosis formation in the microvasculature of various organs. Included in the broad category of TMA are the hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Typical HUS is caused by Escherichia coli O157:H7, which produces the Shiga-like toxins; Stx-1 and Stx-2. In addition to damaging endothelial cells via the inhibition of protein synthesis, Shiga-like toxins also activate endothelial cells to produce inflammatory mediators, amplifying the prothrombogenic state. Although most patients with typical HUS recover renal functions, recent analysis has shown that typical HUS is not a benign disease in the long term. Genetic abnormalities of complement regulatory proteins predispose patients to atypical HUS. Mutations in factor H, membrane cofactor protein, and factor I are known to be associated with atypical HUS. Atypical HUS forms have a poor outcome and show recurrent and progressive courses. Autoimmune IgG inhibitors of a disintegrin and metalloprotease, with thrombospodin-1-like domains (ADAMTS) 13 and mutations of the ADAMTS13 gene lead to the development of TTP. Without treatment, TTP is associated with a very high mortality rate. As it is for atypical HUS, plasma exchange is currently the most feasible treatment for TTP. Etiological diagnosis at the bedside and the development of disease-specific therapeutic modalities will enable us to optimize the management of patients with TMA and improve their prognosis in the future.

Anti-CD20 antibody in thrombotic thrombocytopenic purpura refractory to plasma exchange

Thrombotic thrombocytopenic purpura is a rare condition characterized by microangiopathic haemolytic anaemia, thrombocytopenia, altered neurology, renal impairment and fever. While plasma exchange has reduced mortality from more than 90% to between 10 and 30%, a proportion of cases fail to respond. Rituximab may be efficacious in the management of refractory cases of thrombotic thrombocytopenic purpura. We present two cases in which rituximab was used with successful outcomes. Treatment resulted in resolution of severe clinical and haematological abnormalities in both patients. There has been no relapse after 16 months follow up. Our experience supports the use of rituximab in difficult cases of TTP. Ongoing evaluation of its use is in progress at our institution.

The clinical utility of ADAMTS13 activity, antigen and autoantibody assays in thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) has been linked to a severe deficiency in ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 motif, member 13) activity. Since the identification of ADAMTS13, and its target cleavage sequence in von Willebrand factor (VWF), several novel ADAMTS13 activity, antigen and autoantibody assays have been developed. Our aim was to evaluate the potential use of these novel assays. ADAMTS13 activity and inhibitors were measured by overnight incubation of patient plasma with pure VWF followed by multimer or collagen binding analysis. ADAMTS13 activity (Rapid peptide assay), antigen and immunoglobulin G anti-ADAMTS13 were measured by enzyme-linked immunosorbent assay. 118 samples from seven TTP patients (six adult idiopathic, one congenital) were studied longitudinally during episodes of TTP, their treatment and prophylaxis. ADAMTS13 antigen levels varied considerably between patients and sample times, but in new cases of acute TTP, rapid assays of ADAMTS13 antigen, on serial samples, maybe helpful in confirming the diagnosis. The rapid peptide ADAMTS13 activity assay showed good concordance of results with the older activity assay methods. The change in ADAMTS13 activity mirrored the autoantibody level and in 5/6 acquired TTP cases, a fall in antibody appeared to predict a rise in ADAMTS13 activity, potentially allowing modification of patient management based on autoantibody levels.

Imitators of Severe Preeclampsia

There are several obstetric, medical, and surgical disorders that share many of the clinical and laboratory findings of patients with severe preeclampsia-hemolysis, elevated liver enzymes, and low platelets syndrome. Imitators of severe preeclampsia-hemolysis, elevated liver enzymes, and low platelets syndrome are life-threatening emergencies that can develop during pregnancy or in the postpartum period. These conditions are associated with high maternal mortality, and survivors may face long-term sequelae. Perinatal mortality and morbidity also remain high in many of these conditions. The pathophysiologic abnormalities in many of these disorders include thrombotic microangiopathy, thrombocytopenia, and hemolytic anemia. Some of these disorders include acute fatty liver of pregnancy, thrombotic thrombocytopenic purpura, hemolytic uremic syndrome, and acute exacerbation of systemic lupus erythematosus. Because of the rarity of these conditions during pregnancy and postpartum, the available literature includes only case reports and case series describing these syndromes. Consequently, there are no systematic reviews or randomized trials on these subjects. Differential diagnosis may be difficult due to the overlap of several clinical and laboratory findings of these syndromes. It is important that the clinician make the accurate diagnosis when possible because the management and complications from these syndromes may be different. For example, severe preeclampsia and acute fatty liver of pregnancy are treated by delivery, whereas it is possible to continue pregnancy in those with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome and exacerbation of systemic lupus erythematosus. This review focuses on diagnosis, management, and counseling of women who develop these syndromes based on results of recent studies.

Remission in acute refractory and relapsing thrombotic thrombocytopenic purpura following rituximab is associated with a reduction in IgG antibodies to ADAMTS-13

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder and plasma exchange (PEX) remains the primary treatment modality. Twenty-five patients with acute refractory/relapsing idiopathic TTP received rituximab in conjunction with PEX because of progressive clinical disease or deterioration in laboratory parameters, despite intensive standard therapy. In relapsing TTP, rituximab was started if antibody to ADAMTS-13 (a disintegrin and metalloproteinase with thrombospondin motif-13) was demonstrated during previous episodes. All 25 patients attained complete clinical and laboratory remission in a median of 11 d after initiating rituximab. In 21 cases, ADAMTS-13 activity was within the normal range following rituximab. Inhibitors were detected in 24/25 patients by mixing studies and/or immunoglobulin G (IgG) antibodies to ADAMTS-13 pre-rituximab. There was no evidence of inhibitors and/or IgG activity <10% in 23/25 patients following rituximab. In acute refractory cases, the median number of PEX pre-rituximab and following the first rituximab infusion was 13 and 9, respectively. There have been no infectious complications, despite low CD 19 levels and no relapses. In patients with acute refractory/relapsing idiopathic TTP, rituximab appears to be a safe, effective, targeted therapy with a significant reduction in the requirement for PEX.

Disseminated malignancy misdiagnosed as thrombotic thrombocytopenic purpura: A report of 10 patients and a systematic review of published cases

BACKGROUND

Patients with disseminated malignancy who present with microangiopathic hemolytic anemia and thrombocytopenia may be misdiagnosed as thrombotic thrombocytopenic purpura (TTP), resulting in inappropriate plasma exchange treatment, a procedure with major risk, and delay of appropriate chemotherapy.

PURPOSE

To assess clinical features that may distinguish occult disseminated malignancy from TTP.

PATIENTS AND METHODS

We report the 17-year experience of The Oklahoma TTP-Hemolytic-Uremic Syndrome (HUS) Registry (1989-2005) and a systematic review of previously published case reports.

RESULTS

Ten of 351 patients in the Oklahoma Registry who were initially diagnosed with TTP and treated with plasma exchange were subsequently discovered to have disseminated malignancy. Only one patient had a history of cancer. In these 10 patients, neurologic abnormalities, hematocrit, platelet count, and serum creatinine were not different from the 133 concurrent patients with idiopathic TTP. Patients with disseminated malignancy had a longer duration of symptoms, more frequent presence of respiratory symptoms, higher lactate dehydrogenase levels, and more often failed to respond to plasma exchange treatment. Diagnosis of malignancy was made by bone marrow biopsy in six patients but not until autopsy in two patients. A systematic literature review identified 19 additional patients, reported from 1965 to 2005, in whom TTP or HUS was initially suspected and systemic malignancy was subsequently discovered. Fourteen different malignant disorders were diagnosed in these 29 patients.

CONCLUSIONS

Occult disseminated malignancy may mimic TTP. A search for systemic malignancy, including a bone marrow biopsy, is appropriate when patients with TTP have atypical clinical features or fail to respond to plasma exchange.

Elevated Red Cell Distribution Width in the Diagnosis of Thrombotic Thrombocytopenic Purpura in Patients Presenting with Anemia and Thrombocytopenia

OBJECTIVE

To determine if red cell distribution width (RDW) is elevated in thrombotic thrombocytopenic purpura (TTP) and to evaluate the sensitivity and specificity of such elevation in the diagnosis of TTP.

METHODS

We retrospectively studied red cell distribution width at presentation in 25 consecutive patients with newly diagnosed TTP who were treated with plasmapheresis in our institution between 1997 to 2005. Control patients consisted of 20 consecutive patients without TTP who presented to the emergency room (ER) with anemia and thrombocytopenia.

RESULTS

Patients with TTP had significantly elevated RDW compared with the controls (23.1% versus 17.2% respectively, P = 0.0001). An RDW > 18% had a 95% sensitivity and 70% specificity in the diagnosis of TTP, whereas RDW > 19% had 80% sensitivity and 85% specificity.

CONCLUSIONS

TTP should be suspected in patients presenting with unexplained anemia and thrombocytopenia with an RDW > or = 18%.

[A 32-year-old patient with diarrhoea and acute kidney failure]

A 32-year-old male patient presented in the emergency department of our hospital with acute vomiting and diarrhoea. He reported occasional non-severe diarrhoea over several years in the past. Furthermore, at the time of presentation the patient had had anuria for several days. A prerenal and postrenal origin of the renal failure was excluded. A renal biopsy was performed and histopathological examination displayed findings consistent with a haemolytic-uraemic syndrome but no signs of glomerulonephritis. MRI examination of the small bowel revealed inflammatory alterations typical for Crohn's disease, even without histological verification. We describe haemolytic-waemic syndrome as manifestation of Crohn's disease for the first time.

Targeting the inhibitor of ADAMTS13 in thrombotic thrombocytopenic purpura

There has clearly been an evolution in the treatment of thrombotic thrombocytopenic purpura (TTP) over the past several years based upon a better understanding of the pathophysiology of this disorder. An autoantibody inhibitor of the ADAMTS13 protease and the resulting severe deficiency of ADAMTS13 function seem to be significant risk factors for the development of TTP, a disease increasingly recognized as an autoimmune disorder. Immune-based therapy aimed at suppressing the inhibitor of ADAMTS13 has been applied to the treatment of patients with TTP who are refractory to the standard treatment of plasma exchange and to patients with multiple recurrences of TTP. More recently, immunosuppressive therapy has been used alone as prophylactic therapy to prevent recurrences of acute TTP. This review focuses on the recent developments in the use of rituximab and ciclosporin in the treatment of TTP.