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

TTP: From empiricism for an enigmatic disease to targeted molecular therapies

The 100th anniversary of the first description of Thrombotic Thrombocytopenic Purpura (TTP) as a disease by Dr. Eli Moschcowitz approaches. For many decades, TTP remained mostly a mysterious fatal condition, where diagnosis was often post-mortem. Initially a pentad of symptoms was identified, a pattern that later revealed to be fallible. Sporadic observations led to empiric interventions that allowed for the first impactful breakthrough in TTP treatment, almost 70 years after its first description: the introduction of plasma exchange and infusions as treatments. The main body of knowledge within the field was gathered in the latest three decades: patient registries were set and proved crucial for advancements; the general mechanisms of disease have been described; the diagnosis was refined; new treatments and biomarkers with improvements on prognosis and management were introduced. Further changes and improvements are expected in the upcoming decades. In this review, we provide a brief historic overview of TTP, as an illustrative example of the success of translational medicine enabling to rapidly shift from a management largely based on empiricism to targeted therapies and personalized medicine, for the benefit of patients. Current management options and present and future perspectives in this still evolving field are summarized.

Incidence, diagnosis, and outcome of immune-mediated thrombotic thrombocytopenic purpura: A nationwide survey by the Spanish registry of thrombotic thrombocytopenic purpura

BACKGROUND

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare disease characterized by the presence of anti-ADAMTS13 autoantibodies. Achieving accurate information on incidence and customary disease management is important to provide appropriate diagnostic and therapeutic resources. The aim of this study was to determine the incidence and outcomes of iTTP in Spain.

STUDY DESIGN AND METHODS

A cross-sectional survey was carried out among Spanish hospitals, focused on iTTP patients ≥16 years old attended between 2015 and 2017, and those at follow-up before that interval. Incidence, prevalence, mortality, refractoriness, exacerbations, treatment complications, relapses, and sequelae were estimated.

RESULTS

Forty-two hospitals covering roughly 20 million inhabitants answered the survey and reported 203 episodes (138 newly-diagnosed and 65 relapses), of which 193 (95.1%) were treated. Incidence was 2.67 (95% CI 1.90-3.45) patients per million inhabitants per year and prevalence 21.44 (95% CI% 19.10-23.73) patients per million inhabitants. At diagnosis, ADAMTS13 activity and anti-ADAMTS13 autoantibody were measured in 97% and 84.3% of reported episodes, respectively. Fifteen patients (7.4%) died as a direct consequence of iTTP, 6 of them before receiving any iTTP-specific treatment. Thirty-one (16.1%) of the 193 treated episodes were refractory to plasma exchange and corticosteroids, and 51 (26.4%) suffered at least one exacerbation.

CONCLUSION

iTTP incidence and prevalence were somewhat higher than those documented in neighboring countries. Together with data on treatments and outcomes, this information will allow us to better estimate what is needed to improve diagnosis and prognosis of iTTP patients in Spain.

HIV-associated thrombotic thrombocytopaenic purpura: A retrospective cohort study during the anti-retroviral therapy era

BACKGROUND

HIV-associated thrombotic thrombocytopaenic purpura (TTP) is thought to represent the majority of current TTP diagnoses in South Africa (SA).

AIM

The primary aim was to describe the clinical features and compare the time to remission of TTP in those patients with and without HIV.

DESIGN

A retrospective cohort study conducted at Tygerberg Hospital in Cape Town, SA for the period January 1, 2010 to January 31, 2015.

METHODS

All adult patients requiring ≥5 units of plasma products for ≥1 day during hospitalization were screened for a diagnosis of TTP. Those with a reported clinical diagnosis and/or laboratory evidence of TTP were included in the final analysis.

RESULTS

A total of 52 cases were identified of which 78.8% were HIV-infected. Time to remission was 10 days in the HIV group vs 19 days in the HIV negative group, P = 0.07. Most of the patients were Black females. Fever was more common in those with HIV. Neurological features were common in both groups. The majority in the HIV group was managed exclusively with plasma infusion alone (90.2% vs 45.5%, P < 0.01). There were no differences in the time to remission regardless of treatments received. Anti-retroviral therapy initiation during hospitalization was a predictor for remission. Overall mortality rate was 44.2%.

CONCLUSION

There was no difference in the time to remission in patients with HIV-associated TTP as compared with HIV negative TTP. The high mortality was probably the result of less intensive plasma infusion and therapeutic plasma exchange regimens.

Thrombotic microangiopathy: An unusual cause of renal failure in rheumatoid arthritis

Rheumatoid arthritis (RA) is one of the commonest rheumatological diseases. Renal involvement is not common but can occur as a result of chronic inflammation as part of disease process or drug toxicity. Thrombotic microangiopathy (TMA) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ failure of variable severity. Only a few cases of TMA in patients with RA were reported to date. We describe a 45-year-old female patient with RA who presented with oliguria and edema. Renal biopsy showed TMA with patchy cortical necrosis. She improved with hemodialysis and plasmapheresis.

A phase-II sequential case-series study of all patients presenting to four plasma exchange centres with presumed relapsed/refractory thrombotic thrombocytopenic purpura treated with rituximab

The primary objective of this phase II study was to evaluate the efficacy of rituximab in the management of adult patients with physician-diagnosed presumed thrombotic thrombocytopenic purpura (TTP); relapsed or refractory. We conducted a multicentre study in four Canadian hospital-based apheresis units. Forty patients with presumed TTP (20 refractory and 20 relapsing) were sequentially enrolled and all received rituximab in a standardized manner. A complete response was documented in 14 of 19 refractory patients by week 8 and 15/16 were alive and in remission at 52 weeks (one patient was lost to follow-up, one was a non-responder, and three died). Among relapsing patients, 16/18 had a complete response at week 8 and 18/18 at week 52 (one patient lost to follow-up and one withdrew). At 1 year, all relapsing and 85% of refractory patients survived. Of 38/40 patients who had ADMATS13 testing at study entry, 13/19 refractory and 10/19 relapsing patients had ADAMTS13 < 10% (typical TTP); whereas 6/19 refractory and 9/19 relapsing cases had ADAMTS13 > 10% (other thrombotic microangiopathy; TMA). Refractory-typical TTP in contrast to refractory-other TMA and all relapsing patients treated with plasma exchange and rituximab, were less likely to be responsive and more likely to die or relapse.

Long term outcome and sequelae in patients after acute thrombotic thrombocytopenic purpura episodes

We report on 21 patients with idiopathic thrombotic thrombocytopenic purpura (TTP) whose courses of disease have been followed from the respective diagnosis until now. They had a documented ADAMTS13 activity below 5%, a high autoantibody titer and detectable ultralarge von Willebrand factor (VWF) multimers during their episodes. The initial diagnosis was based on clinical symptoms and on laboratory parameters: thrombocytopenia, haemolytic anaemia, schistocytes and an increased LDH level. 103 acute clinical episodes of 21 TTP-patients during a time period of 30 years are described. Case histories, comorbidities and sequelae were retrospectively documented.

RESULTS, CONCLUSION

Although patients are consistently in a prothrombotic status, clinical acute manifestations only occur after triggering. Most common trigger factors are gastrointestinal infections and pregnancy. The relapse risk per month is 0.026; men have a higher risk for relapses (0.044) than women (0.021). Patients recover physically well, except for renal insufficiency in four cases. Nevertheless, major portion of patients suffers persistently from depression, anxiety disorders and persistent neurocognitive impairments.

The Oklahoma Thrombotic Thrombocytopenic Purpura-haemolytic Uraemic Syndrome Registry. A model for clinical research, education and patient care

The Oklahoma Thrombotic Thrombocytopenic Purpura-Haemolytic Uraemic Syndrome (TTP-HUS) Registry has a 24 year record of success for collaborative clinical research, education, and patient care. This article tells the story of how the Registry began and it describes the Registry's structure and function. The Registry provides a model for using a cohort of consecutive patients to investigate a rare disorder. Collaboration between Oklahoma, United States and Bern, Switzerland has been the basis for successful interpretation of Registry data. Registry data have provided new insights into the evaluation and management of TTP. Because recovery from acute episodes of TTP has been assumed to be complete, the increased prevalence of hypertension, diabetes, depression, and death documented by long-term follow-up was unexpected. Registry data have provided opportunities for projects for students and trainees, education of physicians and nurses, and also for patients themselves. During our follow-up, patients have also educated Registry investigators about problems that persist after recovery from an acute episode of TTP. Most important, Registry data have resulted in important improvements for patient care.

Atypical hemolytic uremic syndrome: what is it, how is it diagnosed, and how is it treated?

Atypical hemolytic uremic syndrome (aHUS) is a rare syndrome of hemolysis, thrombocytopenia, and renal insufficiency. Genetic mutations in the alternate pathway of complement are well recognized as the cause in more than 60% of patients affected by this thrombotic microangiopathy. The identification of aHUS as a disease of the alternate pathway of complement enables directed therapeutic intervention both in the acute and chronic setting and may include one or all of the following: plasma therapy, complement blockade, and liver transplantation. Because aHUS shares many of the presenting characteristics of the other thrombotic microangiopathies, and confirmatory genetic results are not available at the time of presentation, the diagnosis relies heavily on the recognition of a clinical syndrome consistent with the diagnosis in the absence of signs of an alternate cause of thrombotic microangiopathy. Limited understanding of the epidemiology, genetics, and clinical features of aHUS has the potential to delay diagnosis and treatment. To advance our understanding, a more complete characterization of the unique phenotypical features of aHUS is needed. Further studies to identify additional genetic loci for aHUS and more robust biomarkers of both active and quiescent disease are required. Advances in these areas will undoubtedly improve the care of patients with aHUS.

Unexpected frequency of Upshaw-Schulman syndrome in pregnancy-onset thrombotic thrombocytopenic purpura

Pregnancy may be complicated by a rare but life-threatening disease called thrombotic thrombocytopenic purpura (TTP). Most cases of TTP are due to an acquired autoimmune or hereditary (Upshaw-Schulman syndrome [USS]) severe deficiency of a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13 (ADAMTS13). In the present study, we performed a cross-sectional analysis of the national registry of the French Reference Center for Thrombotic Microangiopathies from 2000-2010 to identify all women who were pregnant at their initial TTP presentation. Among 592 adulthood-onset TTP patients with a severe ADAMTS13 deficiency, 42 patients with a pregnancy-onset TTP were included. Surprisingly, the proportion of USS patients (n = 10 of 42 patients [24%]; confidence interval, 13%-39%) with pregnancy-onset TTP was much higher than that in adulthood-onset TTP in general (less than 5%) and was mostly related to a cluster of ADAMTS13 variants. In the present study, subsequent pregnancies in USS patients not given prophylaxis were associated with very high TTP relapse and abortion rates, whereas prophylactic plasmatherapy was beneficial for both the mother and the baby. Pregnancy-onset TTP defines a specific subgroup of patients with a strong genetic background. This study was registered at www.clinicaltrials.gov as number NCT00426686 and at the Health Authority, French Ministry of Health, as number P051064.

The TITAN trial--assessing the efficacy and safety of an anti-von Willebrand factor Nanobody in patients with acquired thrombotic thrombocytopenic purpura

The Phase II TITAN trial is designed to assess the efficacy and safety of an anti-von Willebrand factor (vWF) Nanobody in patients with acquired thrombotic thrombocytopenic purpura (TTP). Nanobodies are a novel class of therapeutic proteins and are based on the smallest functional fragments of single-chain antibodies that occur naturally in the Camelidae family (Nanobody® and Nanobodies® are registered trademarks of Ablynx NV). With vWF implicated in the thrombotic process underlying TTP, an anti-vWF Nanobody may hold significant promise as adjunctive therapy to plasma exchange. Recruitment is currently ongoing, and aims to include a total of 110 patients from countries in Europe, the Middle East, Australia and Northern America.

Thrombotic microangiopathy: current knowledge and outcomes with plasma exchange

The classification of thrombotic microangiopathy has evolved and expanded due to treatment and mechanistic advances. The two basic clinical forms of thrombotic microangiopathy (excluding disseminated intravascular coagulation [DIC]), thrombotic thrombocytopenic purpura (TTP), and hemolytic uremic syndrome (HUS) encompass a wide range of primary and secondary forms. The advent of plasma therapy and the identification of an inhibitor to ADAMTS13 in the idiopathic or acute forms of TTP and its absence in diarrheal HUS have had a major impact on our current classification of thrombotic microangiopathy. In adults, the difficulty of differentiating TTP, which is much more common than HUS and the need for a speedy diagnosis to provide life-saving plasma therapy has resulted in the term TTP/HUS for adult forms of thrombotic microangiopathy that present with unexplained thrombocytopenia and microangiopathic hemolytic anemia without a DIC. In this adult population a primary idiopathic and hereditary form as well as eight known secondary categories or clinical forms of TTP/HUS have been identified. HUS also embraces a primary (atypical HUS) and secondary forms (majority, diarrheal HUS secondary to Escherichia coli 0157:H7). In children, who present with HUS with no preceding history of diarrhea, plasma therapy is also offered on an urgent basis and studies are carried out to determine if they are suffering an abnormality in complement activation that may require eculizumab therapy. The advent of plasma therapy in the treatment of thrombotic microangiopathy has led to a clearer understanding of the role of ADAMTS13, both short- and long-term outcomes and the need for future surveillance and intervention.

Attending rounds: microangiopathic hemolytic anemia with renal insufficiency

The classification of thrombotic microangiopathy has evolved and expanded due to treatment and advances in understanding of the diseases associated with this clinical presentation. The three clinical forms of thrombotic microangiopathy-thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), and disseminated intravascular coagulation-encompass a wide range of disorders that can be classified as either primary (idiopathic) or secondary to another identifiable disease or clinical context. Identification of an inhibitor to a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) in the idiopathic and acute forms of TTP, recognition of the absence of ADAMTS13 inhibition in diarrheal HUS, identification of complement abnormalities in atypical HUS, and a better understanding of the role of plasma therapy, rituximab, and eculizumab therapy have all had a major effect on current understanding of the thrombotic microangiopathies. In this Attending Rounds, a patient with a thrombotic microangiopathy is presented, along with discussion highlighting the difficulty of differentiating TTP from HUS and disseminated intravascular coagulation, the need for a prompt diagnosis, and the role for plasma therapy in appropriately selected patients. The discussion attempts to provide a simple clinical approach to the diagnosis, treatment options, and future course of adults and children suffering from a thrombotic microangiopathy.

Treatment of severe neurological deficits with IgG depletion through immunoadsorption in patients with Escherichia coli O104:H4-associated haemolytic uraemic syndrome: a prospective trial

BACKGROUND

In May 2011, an outbreak of Shiga toxin-producing enterohaemorrhagic E coli O104:H4 in northern Germany led to a high proportion of patients developing post-enteritis haemolytic uraemic syndrome and thrombotic microangiopathy that were unresponsive to therapeutic plasma exchange or complement-blocking antibody (eculizumab). Some patients needed ventilatory support due to severe neurological complications, which arose 1 week after onset of enteritis, suggesting an antibody-mediated mechanism. Therefore, we aimed to assess immunoadsorption as rescue therapy.

METHODS

In our prospective non-controlled trial, we enrolled patients with severe neurological symptoms and confirmed recent E coli O104:H4 infection without other acute bacterial infection or raised procalcitonin concentrations. We did IgG immunoadsorption processing of 12 L plasma volumes on 2 consecutive days, followed by IgG replacement (0·5 g/kg intravenous IgG). We calculated a composite neurological symptom score (lowest score was best) every day and assessed changes before and after immunoadsorption.

FINDINGS

We enrolled 12 patients who initially presented with enteritis and subsequent renal failure; 10 (83%) of 12 patients needed renal replacement therapy by a median of 8·0 days (range 5-12). Neurological complications (delirium, stimulus sensitive myoclonus, aphasia, and epileptic seizures in 50% of patients) occurred at a median of 8·0 days (range 5-15) and mandated mechanical ventilation in nine patients. Composite neurological symptom scores increased in the 3 days before immunoadsorption to 3·0 (SD 1·1, p=0·038), and improved to 1·0 (1·2, p=0·0006) 3 days after immunoadsorption. In non-intubated patients, improvement was apparent during immunoadsorption (eg, disappearance of aphasia). Five patients who were intubated were weaned within 48 h, two within 4 days, and two patients needed continued ventilation for respiratory problems. All 12 patients survived and ten had complete neurological and renal function recovery.

INTERPRETATION

Antibodies are probably involved in the pathogenesis of severe neurological symptoms in patients with E coli O104:H4-induced haemolytic uraemic syndrome. Immunoadsorption can safely be used to rapidly ameliorate these severe neurological complications.

FUNDING

Greifswald University and Hannover Medical School.

A dose ranging phase I/II trial of the von Willebrand factor inhibiting aptamer ARC1779 in patients with congenital thrombotic thrombocytopenic purpura

Congenital thrombotic thrombocytopenic purpura (TTP) is a very rare but potentially life-threatening disorder. This phase I/II trial compared the pharmacokinetics and pharmacodynamics and safety of three different administration modes of the anti-von Willebrand factor (VWF) aptamer ARC1779. This was a prospective clinical trial with a partial cross-over design: three periods comprised subcutaneous injections of 50 mg of ARC1779 on seven subsequent days, a low-dose infusion of ARC1779 (0.002 mg/kg/min) for 24-72 hours and a high-dose infusion (0.004-0.006 mg/kg/min) up to 72 hours. ARC1779 concentrations were determined with high performance liquid chromatography, VWF inhibition was measured with enzyme immunoassay and platelet function was determined with the platelet function analyser (PFA-100) and impedance aggregometry. ARC1779 was well tolerated without any bleeding at concentrations spanning over three orders of magnitude. The daily s.c. injection yielded plasma levels (0.5 μg/ml) of the drug that were too low to sufficiently suppress VWF. The low-dose i.v. infusion increased platelet counts in one patient, whereas the high i.v. dose increased plasma concentrations up to 69 μg/ml, completely blocked free A1 domains, VWF-dependent platelet plug formation and enhanced platelet counts in 2/3 patients. In conclusion, infusion of ARC1779 dose-dependently inhibits VWF-dependent platelet function and during infusion ARC1779 increases or stabilises platelet counts in congenital TTP. However, the tested doses, particularly the daily s.c. injections, did not correct all clinical or laboratory features of TTP.

Successful prevention of thrombotic thrombocytopenic purpura (TTP) relapse using monthly prophylactic plasma exchanges throughout pregnancy in a patient with systemic lupus erythematosus and a prior history of refractory TTP and recurrent fetal loss

BACKGROUND

The occurrence of thrombotic thrombocytopenic purpura (TTP) in the setting systemic lupus erythematosus (SLE) is rare. In women of childbearing age, TTP is associated with high rates of recurrence in pregnancy. Furthermore, both TTP and SLE are associated with a significant risk of adverse pregnancy outcomes.

CASE PRESENTATION

We describe the case of a 36 year old female in her first trimester of pregnancy with a prior history of SLE-associated severe refractory TTP who was treated with a combination of corticosteroids and prophylactic plasma exchanges (PLEX) throughout pregnancy to prevent TTP recurrence. She delivered a healthy infant at 33 weeks of gestation after the onset of preterm labor. There was no evidence of TTP recurrence in the antepartum or postpartum period in this high risk patient.

CONCLUSION

Prophylactic PLEX should be considered as a therapeutic option to prevent recurrent TTP during pregnancy in high risk patients, including patients with previous SLE-associated TTP.

Rituximab pharmacokinetics during the management of acute idiopathic thrombotic thrombocytopenic purpura

BACKGROUND

Increasingly, patients with acute, idiopathic, antibody mediated thrombotic thrombocytopenic purpura (TTP) are being treated with rituximab to achieve a durable remission, however, there is the potential that it is removed by plasma exchange (PEX).

OBJECTIVES

To look at the pharmacokinetics and pharmacodynamics of rituximab in patients with acute idiopathic TTP undergoing PEX.

PATIENTS AND METHODS

Patients who received rituximab for acute idiopathic TTP (group 1, n = 30) and a control group (group 2, n = 3) of TTP patients in remission receiving rituximab electively as maintenance were included. Rituximab levels were measured before/after each infusion, before/after PEX and in follow-up. ADAMTS-13 activity, anti-ADAMTS-13 IgG and CD19% were measured to assess response.

RESULTS

The median number of PEX to remission after rituximab was 10 (range 4-25). In group 1 there was no significant incremental rise in the peak serum rituximab level until dose 4. Trough levels were lower in patients who had had PEX since their last rituximab infusion. In the control group, there was an incremental rise in the peak serum rituximab level and all patients had detectable trough levels. The median fall in rituximab per PEX was 65%. All patients achieved CD19 < 1%. In group 1, the median time to undetectable rituximab was 5 months (range 0-12 months) and to B cell return was 7 months (range 3-24 months). ADAMTS-13 increased and anti-ADAMTS-13 fell after therapy. There were three deaths and two relapses in group 1. Relapse was not temporally related to B cell return.

Komplexe Gerinnungsstörungen

Die thrombotisch-thrombozytopenische Purpura (TTP) und das hämolytischurämische Syndrom (HUS) sind thrombotische Mikroangiopathien, gekennzeichnet durch eine Endothelzellschädigung mit nachfolgender Bildung von Thromben in der Mikrozirkulation mit intravasaler Hämolyse und Thrombozytopenie. Ischämische Organdysfunktionen im Gehirn, den Nieren und anderen Organen Prägen das klinische Bild. Während bei Erwachsenen das Auftreten einer neurologischen Symptomatik zur Diagnose TTP führt, wird bei Kindern mit dem Leitsymptom Nierenversagen die Diagnose HUS gestellt.

Survival and relapse in patients with thrombotic thrombocytopenic purpura

Survival of patients with thrombotic thrombocytopenic purpura (TTP) improved dramatically with plasma exchange treatment, revealing risk for relapse. The Oklahoma TTP Registry is a population-based inception cohort of all 376 consecutive patients with an initial episode of clinically diagnosed TTP (defined as microangiopathic hemolytic anemia and thrombocytopenia with or without signs and symptoms of ischemic organ dysfunctions) for whom plasma exchange was requested, 1989 to 2008. Survival was not different between the first and second 10-year periods for all patients (68% and 69%, P = .83) and for patients with idiopathic TTP (83% and 77%, P = .33). ADAMTS13 activity was measured in 261 (93%) of 282 patients since 1995. Survival was not different between patients with ADAMTS13 activity < 10% (47 of 60, 78%) and patients with 10% or more (136 of 201, 68%, P = .11). Among patients with ADAMTS13 activity < 10%, an inhibitor titer of 2 or more Bethesda units/mL was associated with lower survival (P = .05). Relapse rate was greater among survivors with ADAMTS13 activity < 10% (16 of 47, 34%; estimated risk for relapse at 7.5 years, 41%) than among survivors with ADAMTS13 activity of 10% or more (5 of 136, 4%; P < .001). In 41 (93%) of 44 survivors, ADAMTS13 deficiency during remission was not clearly related to subsequent relapse.

Thrombotic thrombocytopenic purpura at the Johns Hopkins Hospital from 1992 to 2008: clinical outcomes and risk factors for relapse

BACKGROUND

Plasma exchange, the standard treatment for thrombotic thrombocytopenic purpura (TTP), has significantly decreased disease mortality. However, TTP recurs in 20% to 50% of patients who survive the initial episode. We aimed to describe the clinical spectrum of TTP, to determine the valid endpoint for plasma exchange cessation, and to explore the risk factors for disease relapse.

STUDY DESIGN AND METHODS

Using the ICD-9 diagnosis code, we identified patients treated for TTP at the Johns Hopkins Hospital between 1992 and 2008. Complete demographic, clinical, laboratory, treatment, and outcome data were collected from the medical records.

RESULTS

A total of 72 patients were treated for 134 episodes of TTP at the Johns Hopkins Hospital during the study period. With standardized combined immunosuppression and plasma exchange treatment, the all-cause mortality rate was 4%. Lactate dehydrogenase (LDH) normalization lagged behind platelet (PLT) recovery by an average of 9 days and did not predict response. Relapse occurred in 36% of patients during a median follow-up of 30 months with most (76%) occurring in the first 24 months. African American ethnicity was associated with increased risk of relapse (odds ratio = 4.8, p = 0.03).

CONCLUSIONS

Excellent outcomes in patients with TTP are achievable with multimodality therapy. LDH normalization lags behind PLT recovery and might not be an informative endpoint for plasma exchange cessation. Prospective studies are warranted to confirm the influence of race on relapse and identify additional risk factors for adverse outcomes that could be targeted to improve therapeutic outcomes for patients with TTP.

Thrombotic thrombocytopenic purpura in childhood

Thrombotic thrombocytopenic purpura (TTP) is a rare disease, especially in childhood, and has a high mortality rate in the absence of appropriate treatment. It is characterised by microangiopathic haemolytic anaemia and consumptive thrombocytopenia. TTP may be difficult to distinguish from haemolytic uraemic syndrome (HUS) because of similar clinical manifestations and laboratory findings. In the past, TTP and HUS have often been considered to represent variable expressions of a single entity. Our increased understanding of the pathogenesis of TTP has in turn resulted in significant improvements in its treatment and outcomes. Several immunomodulating agents are currently being used with variable outcomes.

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.

The thrombotic thrombocytopenic purpura and hemolytic uremic syndromes: evaluation, management, and long-term outcomes experience of the Oklahoma TTP-HUS Registry, 1989-2007

The Oklahoma thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) Registry, an inception cohort of 382 consecutive patients with TTP-HUS, provides a complete community perspective of these syndromes. TTP, as defined by thrombocytopenia and microangiopathic hemolytic anemia without an alternative etiology, is the appropriate term for all adults. These limited diagnostic criteria are supported by the presenting features of patients with ADAMTS13 deficiency, in whom both neurologic and renal abnormalities are uncommon. HUS is the appropriate term for children who fulfill these diagnostic criteria and who also have renal failure. These definitions are consistent with current management: plasma exchange is the essential treatment for most adults; supportive care is sufficient for children with HUS. Plasma exchange treatment has decreased the mortality of TTP from 90 to 10%. Patients with acquired autoimmune ADAMTS13 deficiency may also require immunosuppressive treatment to achieve a durable remission. Recovery has revealed previously unrecognized long-term risks. Recurrent acute episodes occur in approximately 40% of patients with acquired ADAMTS13 deficiency; most relapses occur within the first year and most patients have only one relapse. Adults with TTP of any etiology have a high risk for persistent minor cognitive abnormalities.