Neuropsychological sequelae of haemolytic uraemic syndrome. Investigators of the HUS Cognitive Study

Neurological involvement in children with hemolytic uremic syndrome

Our objective was to establish the rate of neurological involvement in Shiga toxin-producing Escherichia coli-hemolytic uremic syndrome (STEC-HUS) and describe the clinical presentation, management and outcome. A retrospective chart review of children aged ≤ 16 years with STEC-HUS in Children's Health Ireland from 2005 to 2018 was conducted. Laboratory confirmation of STEC infection was required for inclusion. Neurological involvement was defined as encephalopathy, focal neurological deficit, and/or seizure activity. Data on clinical presentation, management, and outcome were collected. We identified 240 children with HUS; 202 had confirmed STEC infection. Neurological involvement occurred in 22 (11%). The most common presentation was seizures (73%). In the neurological group, 19 (86%) were treated with plasma exchange and/or eculizumab. Of the 21 surviving children with neurological involvement, 19 (91%) achieved a complete neurological recovery. A higher proportion of children in the neurological group had renal sequelae (27% vs. 12%, P = .031). One patient died from multi-organ failure.Conclusion: We have identified the rate of neurological involvement in a large cohort of children with STEC-HUS as 11%. Neurological involvement in STEC-HUS is associated with good long-term outcome (complete neurological recovery in 91%) and a low case-fatality rate (4.5%) in our cohort. What is Known: • HUS is associated with neurological involvement in up to 30% of cases. • Neurological involvement has been reported as predictor of poor outcome, with associated increased morbidity and mortality. What is New: • The incidence of neurological involvement in STEC-HUS is 11%. • Neurological involvement is associated with predominantly good long-term outcome (90%) and a reduced case-fatality rate (4.5%) compared to older reports.

Frequency of neurological involvement in patients with/without diarrhea hemolytic uremic syndrome: A Systematic review and meta-analysis

Background: Diarrhea-associated-hemolytic-uremic-syndrome (D+HUS) is a common from of HUS. Central-nervous-system (CNS) involvement is one of the most common extrarenal organ involvements in children with D+HUS. This systematic review and meta-analysis aim to recognize the frequency of neurological complications in pts with HUS. Methods: Databases of PubMed, Embase, and Web of Science were searched systematically to find the papers on neurological involvement in HUS pts. Two researchers independently assessed the papers' quality and extracted data. CMA v. 2.2.064. was used for data analysis. Heterogeneity was evaluated using the I-squared (I2) test, and a fixed/random-effects model was used when appropriate. Results: In this review, 21 studies including 2,189 participants with a median age between 1.3-40-year-old, entered the meta-analysis. The meta-analysis in D+HUS patients indicated 27.0% with neurological complications (95% CI, 22.0%-32.6%), 25.5% of symptoms weren't categorized (95% CI, 15.9%-38.3%), 20.8% of them developed the seizures (95% CI, 2.3%-74.4%). In D-HUS pts, 20.8% of them were presented neurological symptoms (95% CI, 17.9%-24.0%), of which 29.0% weren't categorized (95% CI, 19.2%-41.2%), 17.5% of pts got into coma (95% CI, 9.6%-29.7%), 5.6 % showed hemiparesis (95% CI, 2.8%-10.9%), 17.2% experienced lethargy (95% CI, 5.2%-44.1%), 30.5% developed the seizures (95% CI, 18.2%-46.2%), 7.4% manifested speech abnormalities (95% CI, 0.2%-7.22%), 6.4% of D-HUS pts presented visual-disturbances (95% CI, 3.4%-11.6%). Conclusion: This systematic review and meta-analysis indicated more than one-fourth of both D+HUS and D-HUS patients were presented with neurological symptoms, and the most prevalent symptoms were seizures, which can lead to an epilepsy sequel.

Shiga Toxin-Associated Hemolytic Uremic Syndrome: Specificities of Adult Patients and Implications for Critical Care Management

Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome (STEC-HUS) is a form of thrombotic microangiopathy secondary to an infection by an enterohemorrhagic E. coli. Historically considered a pediatric disease, its presentation has been described as typical, with bloody diarrhea at the forefront. However, in adults, the clinical presentation is more diverse and makes the early diagnosis hazardous. In this review, we review the epidemiology, most important outbreaks, physiopathology, clinical presentation and prognosis of STEC-HUS, focusing on the differential features between pediatric and adult disease. We show that the clinical presentation of STEC-HUS in adults is far from typical and marked by the prevalence of neurological symptoms and a poorer prognosis. Of note, we highlight knowledge gaps and the need for studies dedicated to adult patients. The differences between pediatric and adult patients have implications for the treatment of this disease, which remains a public health threat and lack a specific treatment.

Shiga Toxin-Associated Hemolytic Uremic Syndrome: A Narrative Review

The severity of human infection by one of the many Shiga toxin-producing Escherichia coli (STEC) is determined by a number of factors: the bacterial genome, the capacity of human societies to prevent foodborne epidemics, the medical condition of infected patients (in particular their hydration status, often compromised by severe diarrhea), and by our capacity to devise new therapeutic approaches, most specifically to combat the bacterial virulence factors, as opposed to our current strategies that essentially aim to palliate organ deficiencies. The last major outbreak in 2011 in Germany, which killed more than 50 people in Europe, was evidence that an effective treatment was still lacking. Herein, we review the current knowledge of STEC virulence, how societies organize the prevention of human disease, and how physicians treat (and, hopefully, will treat) its potentially fatal complications. In particular, we focus on STEC-induced hemolytic and uremic syndrome (HUS), where the intrusion of toxins inside endothelial cells results in massive cell death, activation of the coagulation within capillaries, and eventually organ failure.

Extrarenal manifestations of the hemolytic uremic syndrome associated with Shiga toxin-producing Escherichia coli (STEC HUS)

Hemolytic uremic syndrome is commonly caused by Shiga toxin-producing Escherichia coli (STEC). Up to 15% of individuals with STEC-associated hemorrhagic diarrhea develop hemolytic uremic syndrome (STEC HUS). Hemolytic uremic syndrome (HUS) is a disorder comprising of thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury. The kidney is the most commonly affected organ and approximately half of the affected patients require dialysis. Other organ systems can also be affected including the central nervous system and the gastrointestinal, cardiac, and musculoskeletal systems. Neurological complications include altered mental status, seizures, stroke, and coma. Gastrointestinal manifestations may present as hemorrhagic colitis, bowel ischemia/necrosis, and perforation. Pancreatitis and pancreatic beta cell dysfunction resulting in both acute and chronic insulin dependant diabetes mellitus can occur. Thrombotic microangiopathy (TMA) in cardiac microvasculature and troponin elevation has been reported, and musculoskeletal involvement manifesting as rhabdomyolysis has also been described. Extrarenal complications occur not only in the acute setting but may also be seen well after recovery from the acute phase of HUS. This review will focus on the extrarenal complications of STEC HUS. To date, management remains mainly supportive, and while there is no specific therapy for STEC HUS, supportive therapy has significantly reduced the mortality rate.

Extrarenal manifestations of the hemolytic uremic syndrome associated with Shiga toxin-producing Escherichia coli (STEC HUS)

Hemolytic uremic syndrome is commonly caused by Shiga toxin-producing Escherichia coli (STEC). Up to 15% of individuals with STEC-associated hemorrhagic diarrhea develop hemolytic uremic syndrome (STEC HUS). Hemolytic uremic syndrome (HUS) is a disorder comprising of thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury. The kidney is the most commonly affected organ and approximately half of the affected patients require dialysis. Other organ systems can also be affected including the central nervous system and the gastrointestinal, cardiac, and musculoskeletal systems. Neurological complications include altered mental status, seizures, stroke, and coma. Gastrointestinal manifestations may present as hemorrhagic colitis, bowel ischemia/necrosis, and perforation. Pancreatitis and pancreatic beta cell dysfunction resulting in both acute and chronic insulin dependant diabetes mellitus can occur. Thrombotic microangiopathy (TMA) in cardiac microvasculature and troponin elevation has been reported, and musculoskeletal involvement manifesting as rhabdomyolysis has also been described. Extrarenal complications occur not only in the acute setting but may also be seen well after recovery from the acute phase of HUS. This review will focus on the extrarenal complications of STEC HUS. To date, management remains mainly supportive, and while there is no specific therapy for STEC HUS, supportive therapy has significantly reduced the mortality rate.

Rescue from Stx2-Producing E. coli-Associated Encephalopathy by Intravenous Injection of Muse Cells in NOD-SCID Mice

Shiga toxin-producing Escherichia coli (STEC) causes hemorrhagic colitis, hemolytic uremic syndrome, and acute encephalopathies that may lead to sudden death or severe neurologic sequelae. Current treatments, including immunoglobulin G (IgG) immunoadsorption, plasma exchange, steroid pulse therapy, and the monoclonal antibody eculizumab, have limited effects against the severe neurologic sequelae. Multilineage-differentiating stress-enduring (Muse) cells are endogenous reparative non-tumorigenic stem cells that naturally reside in the body and are currently under clinical trials for regenerative medicine. When administered intravenously, Musecells accumulate to the damaged tissue, where they exert anti-inflammatory, anti-apoptotic, anti-fibrotic, and immunomodulatory effects, and replace damaged cells by differentiating into tissue-constituent cells. Here, severely immunocompromised non-obese diabetic/severe combined immunodeficiency (NOD-SCID) mice orally inoculated with 9 × 10⁹ colony-forming units of STEC O111 and treated 48 h later with intravenous injection of 5 × 10⁴ Muse cells exhibited 100% survival and no severe after-effects of infection. Suppression of granulocyte-colony-stimulating factor (G-CSF) by RNAi abolished the beneficial effects of Muse cells, leading to a 40% death and significant body weight loss, suggesting the involvement of G-CSF in the beneficial effects of Muse cells in STEC-infected mice. Thus, intravenous administration of Muse cells could be a candidate therapeutic approach for preventing fatal encephalopathy after STEC infection.

[Hemolytic and uremic syndrome and related thrombotic microangiopathies: Epidemiology, pathophysiology and clinics]

Thrombotic microangiopathies (TMA) represent an eclectic group of conditions, which share hemolytic anemia and thrombocytopenia as a common defining basis. Remarkable breakthroughs in the physiopathological setting have allowed for a thorough recomposition of the disparate syndromes, which form the constellation of TMA. In this view, clinicians now discriminate thrombocytopenic thrombotic purpura (TTP) defined by a severe deficiency in ADAMTS13, which is rarely associated with a severe renal involvement and the hemolytic and uremic syndrome (HUS) in which renal impairment is the most prominent clinical feature. HUS can result from toxins stemming from bacterial infections of the digestive tract, alternate complement pathway abnormalities, metabolic or coagulation disorders or, lastly, drug and various toxic compounds. The diverse forms of HUS reflect the insights gained in the understanding of the pathophysiological mechanisms underpinning TMA. In this first part, a broad overview of the epidemiological, physiopathological and clinical aspects of HUS and related TMA syndromes is presented.

Long-term health-related quality of life and psychological adjustment in children after haemolytic-uraemic syndrome

BACKGROUND

In children after haemolytic-uraemic syndrome (HUS), little is known about long-term health-related quality of life (HRQoL) and psychological adjustment as defined by behavioural problems, depressive symptoms and post-traumatic stress symptoms.

METHODS

Sixty-two paediatric patients with a history of HUS were included in this study. Medical data of the acute HUS episode were retrieved retrospectively from hospital records. Data on the clinical course at study investigation were assessed by clinical examination and laboratory evaluation. HRQoL and psychological adjustment data were measured by standardised, parent- and self-reported questionnaires.

RESULTS

Haemolytic-uraemic syndrome was diagnosed at a mean of 6.5 years before the initiation of the study (standard deviation 2.9, range 0.1-15.7) years. Among the preschool children, parents reported that their child was less lively and energetic (HRQoL emotional dimension), while no increased behavioural problems were reported. In the school-age children, self- and proxy-reported HRQoL was well within or even above the norms, while increased total behavioural problems were found. The school-age children reported no increased depression scores. Also none of the children met the criteria for full or partial HUS-associated posttraumatic stress disorder.

CONCLUSIONS

Healthcare providers should be particularly alert to behavioural problems in school-age children with a history of HUS and to lower HRQoL in preschool children.

Neurological Sequelae in Adults After E coli O104: H4 Infection-Induced Hemolytic-Uremic Syndrome

In an outbreak of shiga toxin-producing Escherichia coli infections and associated hemolytic-uremic syndrome (STEC O104:H4) in Germany in the year 2011 neurological complications in adult patients occurred unexpectedly frequent, ranging between 48% and 100% in different patient groups. Few is known about the long-term effects of such complications and so we performed follow-up exams on 44 of the patients treated for STEC-HUS at Hannover Medical Scool in this observational study. Standardized follow-up exams including neurological and neuropsychological assessments, laboratory testing, magnetic resonance imaging (MRI), and EEG were carried out. Subgroups were examined 2 (n = 34), 7 (n = 22), and 19 (n = 23) months after disease onset. Additionally, at the 19-month follow-up, quality of life, sleep quality, and possible fatigue were assessed.Nineteen months after disease onset 31 patients were reassessed, 22 of whom still suffered from symptoms such as fatigue, headache, and attention deficits. In the neuropsychological assessments only 39% of the patients performed normal, whereas 61% scored borderline pathological or lower. Upon reviewal, the follow-up data most prominently showed a secondary decline of cognitive function in about one-quarter of the patients. Outcome was not related to treatment or laboratory data in the acute phase of the disease nor length of hospitalization. Prognosis of STEC-HUS associated brain dysfunction in adults with regard to severity of symptoms is mostly good; some patients however still have not made a full recovery. Patients' caretakers have to be aware of possible secondary decline of brain function as was observed in this study.

Eculizumab in Typical Hemolytic Uremic Syndrome (HUS) With Neurological Involvement

In typical hemolytic uremic syndrome (HUS) approximately 25% of patients show central nervous system (CNS) involvement often leading to serious long-term disabilities. We used the C5-complement inhibitor Eculizumab as rescue therapy. From 2011 to 2014, 11 children (median age 22 months, range 11-175) with enterohemorrhagic Escherichia coli-positive HUS requiring dialysis who had seizures (11/11) and/or were in a stupor or coma (10/11) were treated with Eculizumab. Two patients enrolled on the Safety and Efficacy Study of Eculizumab in Shiga-Toxin Producing E coli Hemolytic-Uremic Syndrome (STEC-HUS) each received 6 doses of Eculizumab, 3 patients 2 doses, and 6 patients 1 dose. Laboratory diagnostics of blood samples and magnetic resonance imaging (MRI) were performed as per center practice. Data were analyzed retrospectively. Cranial MRI was abnormal in 8 of 10 patients with findings in the basal ganglia and/or white matter. A 2-year-old boy with severe cardiac involvement and status epilepticus needed repeated cardio-pulmonary resuscitation and extracorporeal membrane oxygenation. He died 8 days after start of Eculizumab treatment. Two patients with hemorrhagic colitis and repeated seizures required artificial ventilation for 6 and 16 days, respectively. At the time of discharge, 1 patient showed severe neurological impairment and 1 mild neurological impairment. The 8 surviving patients experienced no further seizures after the first dose of Eculizumab. Three patients showed mild neurological impairment at discharge, whilst the remaining 5 showed no impairment. The platelets normalized 4 days (median) after the first dose of Eculizumab (range 0-20 days). The mean duration of dialysis after the first dose of Eculizumab was 14.1 ± 6.1 days. In children with typical HUS and CNS involvement early use of Eculizumab appears to improve neurological outcome. In severe HUS cases which progress rapidly with multiple organ involvement, late treatment with Eculizumab seems to show less benefit. We speculate that prophylactic Eculizumab therapy before development of neurological symptoms could be advantageous.

Neurodevelopmental long-term outcome in children after hemolytic uremic syndrome

BACKGROUND

To investigate the long-term neurodevelopmental outcome in children after hemolytic uremic syndrome (HUS) and to compare outcome dependent on central nervous system (CNS) involvement during HUS.

METHODS

A single-center retrospective cohort of 47 children was examined at a median age of 10.6 (range 6-16.9) years and a median follow-up of 7.8 (range 0.4-15.3) years after having had HUS. Intellectual performance was assessed with the German version of the Wechsler Intelligence Scale 4th version and neuromotor performance with the Zurich Neuromotor Assessment (ZNA). The occurrence of neurological symptoms during the acute phase of HUS was evaluated retrospectively.

RESULTS

Mean IQ of the whole study population fell within the normal range (median full scale IQ 104, range 54-127). Neuromotor performance was significantly poorer in the domains "adaptive fine," "gross motor," "static balance" (all p < 0.05) and "associated movements" (p < 0.001); only the "pure motor" domain was within the normal reference range. Neurological findings occurred in 16/47 patients (34 %) during acute HUS. Neurodevelopmental outcome was not significantly different between children with or without CNS involvement.

CONCLUSIONS

Our follow-up of children after HUS showed a favorable cognitive outcome. However, neuromotor outcome was impaired in all study participants. Neurological impairment during acute HUS was not predictive of outcome.

Neurological involvement in children with E. coli O104:H4-induced hemolytic uremic syndrome

BACKGROUND

The aim of this study was to analyze the neurological involvement and outcome in pediatric patients with hemolytic uremic syndrome (HUS) during the 2011 epidemic caused by Escherichia coli O104:H4.

METHODS

Clinical data and data from magnetic resonance imaging (MRI) scans and electroencephalography (EEG) during the acute phase of the disease and during follow-up at 3 and 6 months were analyzed in 50 patients. Twenty-five of these patients underwent neuropsychological testing (WISC IV) during follow-up.

RESULTS

Neurological involvement (stupor or coma, seizures, visual disturbances, paresis, myocloni) was initially observed in 14/50 (28%) patients. One patient died. EEG abnormalities were more frequent in patients with neurological involvement than in those without (12/14 vs. 13/25, respectively). Cranial MRI scans were analyzed in nine patients with neurological involvement, of whom five showed abnormal findings. At the 3- and 6-month follow-ups, EEG abnormalities were found in 14/40 (35%) and 7/36 (19%) patients, respectively, whereas 28/42 (67%) and 17/39 (44%) patients, respectively, complained about on-going reduced performance. Neuropsychological testing showed a slightly lower global intelligence quotient in patients with neurological involvement versus those without (113.4 ± 2.8 vs. 119.4 ± 1.8, respectively).

CONCLUSIONS

Neurological involvement was frequent in our cohort. Accordingly, the incidence of pathological EEG findings was high, even in patients without clinical signs of neurological involvement. Nevertheless, major neurological sequelae were rare, and neuropsychological outcome was favorable after 6 months.

Neuropsychological outcome after complicated Shiga toxin-producing Escherichia coli infection

Background

The diarrhea associated hemolytic uremic syndrome (HUS) is a major cause of acute uremic failure in children, but not very common in adults. The enterohaemorrhagic Escherichia coli -epidemic in Germany in 2011 affected mostly young and healthy adults. While their immediate deficits have been published, not much is known about the time course and degree of recovery concerning cognitive and behavioral impairment.

Methods and Findings

Twenty patients with Shiga toxin –producing Escherichia coli infection and neurological symptoms underwent comprehensive neuropsychological assessment 3 months and 1 year after the acute disease. Overall, there was an excellent recovery of cognitive functions. In a detailed neuropsychological analysis no significant deficits could be noticed 1 year after the infection in terms of cognitive function, alertness, executive functions and speech. Interestingly there were no correlations between different indicators for severity of disease (hemoglobin and creatinin levels, days of hospitalization, neurological symptoms and MRI changes) and neuropsychological outcome. However, there were a small number of patients with limitations in every day and professional life even one year after the acute disease.

Conclusions

Our study does not provide definitive answers regarding risk factors for these limitations. Still since Shiga toxin –producing Escherichia coli infection is a rare condition in adults, the information this study provides is important for the clinical practice. On one hand for consulting patients and on the other to raise the awareness of the physicians to possible long term complains and the consideration of neuropsychological assessment and supportive psychological treatment.

Hemolytic uremic syndrome

The thrombotic microangiopathies include both hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Although debate exists as to whether these are separate entities or a spectrum of disease, both result in the clinical picture of thrombocytopenia, hemolytic anemia, and varying degrees of renal and neurologic involvement. Etiology of HUS includes diarrheal infection due to Shiga toxin-producing bacteria, complement deficiency, pneumococcal infection, and cobalamin deficiency. In disease ascribed to TTP, the main etiologic factor is deficiency of an enzyme known as a disintegrin-like and metalloprotease with thrombospondin type 1 repeats, number 13 (ADAMTS-13). The clinical manifestations may vary, but neurologic involvement can be significant, with reports of hypertensive encephalopathy, seizures, thrombosis and infarct. In nondiarrheal forms of disease, recurrence may occur and clinical diagnosis is essential in order to provide a targeted therapy for the suspected etiology. Therapies include supportive care, cobalamin supplementation, as well as plasma infusion and exchange. End stage renal disease may result and transplantation is curative for some forms of the disease. More recent research focuses on targeted immunotherapy to prevent autoantibody prevention. As of yet, there is no one cure for these potentially devastating diseases, and diagnosis and treatment selection presents a challenge to the clinician.

Long-term consequences of foodborne infections

Foodborne infections with Campylobacter, E. coli O157:H7, Listeria monocytogenes, Salmonella, Shigella, Toxoplasma gondii, and other pathogens can result in long-term sequelae to numerous organ systems. These include irritable bowel syndrome, inflammatory bowel disease, reactive arthritis, hemolytic uremic syndrome, chronic kidney disease, Guillain-Barré Syndrome, neurological disorders from acquired and congenital listeriosis and toxoplasmosis, and cognitive and developmental deficits due to diarrheal malnutrition or severe acute illness. A full understanding of the long-term sequelae of foodborne infection is important both for individual patient management by clinicians, as well as to inform food safety and public health decision making.

Treatment of atypical hemolytic uremic syndrome and thrombotic microangiopathies: a focus on eculizumab

Uncontrolled complement activation is central to the occurrence of atypical hemolytic uremic syndrome (aHUS) and can result in thrombotic microangiopathies (TMAs). These terms encompass a group of heterogenic inherited or acquired diseases that recent research suggests may be triggered by the complement cascade. Pathogenetic triggers of complement activation include immunologic disorders, genetics, infections, systemic diseases, pregnancy, drug administration, metabolic diseases, transplantation, or triggers of mixed cause. Hallmarks of aHUS and other TMAs include increased vascular endothelium thromboresistance, leukocyte adhesion to damaged endothelium, complement consumption, coagulation abnormalities, and vascular shear stress, whereas common end points of these mechanisms include hemolytic anemia, thrombocytopenia with microvascular infarction, and predisposition for decreased kidney function and other organ involvement. The central role of the complement cascade as a disease trigger suggests a possible therapeutic target. Eculizumab, a first-in-class humanized monoclonal anti-C5 antibody that has been successful in the treatment of paroxysmal nocturnal hemoglobinuria, a disorder of complement-induced hemolytic anemia, received approval for the treatment of aHUS in the United States and Europe in late 2011. We review the treatment of aHUS and other TMAs, focusing on the role of eculizumab, including its pharmacology, mechanism of action, and approved dosing recommendations and health economic considerations. Finally, the potential for future indications for eculizumab use in other complement-driven diseases is discussed.

Renal and neurological involvement in typical Shiga toxin-associated HUS

Shiga toxin-producing Escherichia coli-associated haemolytic uraemic syndrome (STEC-HUS) is one of the most important causes of acute kidney injury in patients of all ages, especially in children. It can occur sporadically or in outbreaks. STEC-HUS is a systemic illness caused by toxin-mediated injury to the vascular endothelium and a generalized inflammatory response. The kidney and the brain are the two primary target organs. Nearly 40% of patients with STEC-HUS require at least temporary renal replacement therapy and up to 20% will have permanent residual kidney dysfunction. Neurological injury can be sudden and severe and is the most frequent cause of acute mortality in patients with STEC-HUS. Over the past 30 years, a wide range of inflammatory mediators have been linked to the pathogenesis of STEC-HUS and associated renal and neurological complications. Recently, evidence has accumulated that abnormal activation of the alternative pathway of complement occurs in patients with STEC-HUS. In the large outbreak of STEC-HUS caused by E. coli O104:H4 that occurred in Germany in May 2011, a large number of patients received eculizumab, a monoclonal antibody directed against C5, in an open-label manner. We describe the experience with eculizumab under these emergent circumstances at one large centre.

Experiences with HUS in Canada: what have we learned about childhood HUS in Canada?

Experiences with childhood hemolytic uremic syndrome (HUS) in Canada will focus on the development of the Canadian Pediatric Kidney Disease Research Centre (CPKDRC) and the results of our collaborative research over a 13-year period (1985-1998).

Thrombotic thrombocytopenic purpura and the hemolytic-uremic syndrome

Large and unusually large von Willebrand factor (vWf) multimers may be responsible for systemic platelet aggregation in thrombotic thrombocytopenic purpura (TTP). This possibility is supported by studies that show deficient vWf-cleaving metalloproteinase and increased platelet-vWf binding during TTP episodes. In acute idiopathic TTP, decreased vWf metalloproteinase is the result of autoantibodies against the enzyme. In familial and acquired hemolytic-uremic syndrome, vWf-cleaving metalloproteinase activity is normal. A deficiency or defect in factor H, which normally dampens the activation of C3 via the alternative complement pathway, has been seen in some patients with familial hemolytic-uremic syndrome. Ticlopidine therapy is an important risk factor for TTP.