Secondary Hemolytic Uremic Syndrome Research Articles

Atypical Hemolytic-Uremic Syndrome: Genetic Basis, Clinical Manifestations, and a Multidisciplinary Approach to Management.

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy (TMA) defined by the triad of hemolytic anemia, thrombocytopenia, and acute kidney injury. Microthrombi develop in the glomerular capillaries secondary to endothelial damage and exert shear stress on red blood cells, consume platelets, and contribute to renal dysfunction and failure. Per current understanding of pathophysiology, HUS is classified into infectious, secondary, and atypical disease. The most common etiology is infectious sequelae of Shiga toxin-producing Escherichia coli (STEC); other causative organisms include shigella and salmonella. Secondary HUS arises from cancer, chemotherapy, solid organ and hematopoietic stem cell transplant, pregnancy, or autoimmune disorders. Primary atypical hemolytic-uremic syndrome (aHUS) is associated with genetic mutations in complement and complement regulatory proteins. Under physiologic conditions, complement regulators keep the alternative complement system continuously active at low levels. In times of inflammation, mutations in complement-related proteins lead to uncontrolled complement activity. The hyperactive inflammatory state leads to glomerular endothelial damage, activation of the coagulation cascade, and TMA findings. Atypical hemolytic-uremic syndrome is a rare disorder with a prevalence of 2.21 to 9.4 per million people aged 20 years or younger; children between the ages of 0 and 4 are most affected. Multidisciplinary health care is necessary for timely management of its extra-renal manifestations. These include vascular disease of the heart, brain, and skin, pulmonary hypertension and hemorrhage, and pregnancy complications. Adequate screening is required to monitor for sequelae. First-line treatment is the monoclonal antibody eculizumab, but several organ systems may require specialized interventions and coordination of care with sub-specialists.

Pharmacological Management of Atypical Hemolytic Uremic Syndrome in Pediatric Patients: Current and Future.

Atypical hemolytic uremic syndrome is a thrombotic microangiopathy characterized by hemolysis, thrombocytopenia, and acute kidney injury, usually caused by alternative complement system overactivation due to pathogenic genetic variants or antibodies to components or regulatory factors in this pathway. Previously, a lack of effective treatment for this condition was associated with mortality, end-stage kidney disease, and the risk of disease recurrence after kidney transplantation. Plasma therapy has been used for atypical hemolytic uremic syndrome treatment with inconsistent results. Complement-blocking treatment changed the outcome and prognosis of patients with atypical hemolytic uremic syndrome. Early administration of eculizumab, a monoclonal C5 antibody, leads to improvements in hematologic, kidney, and systemic manifestations in patients with atypical hemolytic uremic syndrome, even with apparent dialysis dependency. Pre- and post-transplant use of eculizumab is effective in the prevention of atypical hemolytic uremic syndrome recurrence. Evidence on eculizumab use in secondary hemolytic uremic syndrome cases is controversial. Recent data favor the restrictive use of eculizumab in carefully selected atypical hemolytic uremic syndrome cases, but close monitoring for relapse after drug discontinuation is emphasized. Prophylaxis for meningococcal infection is important. The long-acting C5 monoclonal antibody ravulizumab is now approved for atypical hemolytic uremic syndrome treatment, enabling a reduction in the dosing frequency and improving the quality of life in patients with atypical hemolytic uremic syndrome. New strategies for additional and novel complement blockage medications in atypical hemolytic uremic syndrome are under investigation.

Vascular Occlusion in Kidney Biopsy Is Characteristic of Clinically Manifesting Thrombotic Microangiopathy.

Thrombotic microangiopathy (TMA) can sometimes manifest only histologically. Our aim was to retrospectively compare biopsy-proven adult TMA patients showing only histological (h-TMA) or both histological and clinical (c-TMA) TMA in 2006–2017. All native kidney biopsies with TMA were included. Biopsies were re-evaluated by light and electron microscopy, and immunofluorescence. Clinical characteristics, laboratory variables, and treatments were recorded from the electronic medical database. Patients were categorized into h-TMA and c-TMA and these groups were compared. In total, 30 biopsy-proven cases among 7943 kidney biopsies were identified and, of these, 15 had h-TMA and 15 c-TMA. Mean follow-up was 6.3 y, and 73.3% had secondary hemolytic uremic syndrome (HUS) and the rest were atypical HUS. Patient characteristics, treatments, and kidney, and patient survival in the groups were similar. Statistically significant differences were found in histological variables. Vascular myxoid swelling and vascular onion-skinning were almost exclusively detected in c-TMA and, thus, vascular occlusive changes indicate clinically apparent rather than merely histological TMA. In addition, regardless of clinical presentation, kidney and patient survival times were similar in the patient groups highlighting the importance of a kidney biopsy in the case of any kidney-related symptoms.

Hemolytic uremic syndrome: An updated review

Hemolytic uremic syndrome (HUS) is a microangiopathic thrombotic disease. HUS is classified into typical, secondary, and atypical types. All types are characterized by thrombocytopenia, acute kidney impairment, and hemolysis. Infection with Shiga toxin from Escherichia coli causes typical HUS. Atypical HUS is frequently caused by abnormal complement activation via the alternative pathway because of gene mutations or autoantibodies synthesis. Secondary HUS accompanies post-transplantation, autoimmunity, cancer, etc. Endothelial cell injury initiates cells destruction stimulates procoagulant state, which activates platelet and thrombus generation, producing ischemic tissue injury.
 HUS pathogenesis is the result of an ineffective complement activation cycle that causes endothelial cells damage, activating platelet and thrombus formation. In some atypical HUS cases, interrupting the pathogenesis cycle of HUS by inhibiting complement activation might be beneficial, but not in those with gene mutations and patients with typical or secondary HUS. Hence, the pathogenesis of HUS types understanding is required; therefore, a comprehensive review of the differences and resemblances between the HUS types will be discussed and updated.

Complement Blockade Is a Promising Therapeutic Approach in a Subset of Critically Ill Adult Patients with Complement-Mediated Hemolytic Uremic Syndromes.

Thrombotic microangiopathy (TMA) gathers consumptive thrombocytopenia, mechanical haemolytic anemia, and organ damage. Hemolytic uremic syndromes (HUS) are historically classified as primary or secondary to another disease once thrombotic thrombocytopenic purpura (TTP), Shiga-toxin HUS, and cobalamin C-related HUS have been ruled out. Complement genetics studies reinforced the link between complement dysregulation and primary HUS, contributing to reclassifying some pregnancy- and/or post-partum-associated HUS and to revealing complement involvement in severe and/or refractory hypertensive emergencies. By contrast, no firm evidence allows a plausible association to be drawn between complement dysregulation and Shiga-toxin HUS or other secondary HUS. Nevertheless, rare complement gene variants are prevalent in healthy individuals, thus providing an indication that an investigation into complement dysregulation should be carefully balanced and that the results should be cautiously interpreted with the help of a trained geneticist. Several authors have suggested reclassifying HUS in two entities, regardless of they are complement-mediated or not, since the use of eculizumab, an anti-C5 antibody, dramatically lowers the proportion of patients who die or suffer from end-stage renal disease within the year following diagnosis. Safety and the ideal timing of eculizumab discontinuation is currently under investigation, and the long-term consequences of HUS should be closely monitored over time once patients exit emergency departments.

The Syndromes of Thrombotic Microangiopathy: A Critical Appraisal on Complement Dysregulation.

Thrombotic microangiopathy (TMA) is a rare and potentially life-threatening condition that can be caused by a heterogeneous group of diseases, often affecting the brain and kidneys. TMAs should be classified according to etiology to indicate targets for treatment. Complement dysregulation is an important cause of TMA that defines cases not related to coexisting conditions, that is, primary atypical hemolytic uremic syndrome (HUS). Ever since the approval of therapeutic complement inhibition, the approach of TMA has focused on the recognition of primary atypical HUS. Recent advances, however, demonstrated the pivotal role of complement dysregulation in specific subtypes of patients considered to have secondary atypical HUS. This is particularly the case in patients presenting with coexisting hypertensive emergency, pregnancy, and kidney transplantation, shifting the paradigm of disease. In contrast, complement dysregulation is uncommon in patients with other coexisting conditions, such as bacterial infection, drug use, cancer, and autoimmunity, among other disorders. In this review, we performed a critical appraisal on complement dysregulation and the use of therapeutic complement inhibition in TMAs associated with coexisting conditions and outline a pragmatic approach to diagnosis and treatment. For future studies, we advocate the term complement-mediated TMA as opposed to the traditional atypical HUS-type classification.

P1805UNEXPECTD COMPLEMENT GENES ABNORALITIES IN CHILDREN WITH SECONDARY HEMOLITIC UREMIC SYNDROME

Abstract Background and Aims Secondary hemolytic-uremic syndrome (HUS) is currently defined in the absence of genetic defects in complement genes (primary or atypical HUS, aHUS) or Shiga-toxin producing E. Coli infection (STEC-HUS). However, the role of complement genes abnormalities in secondary HUS is still a matter of debate as results coming from studies performed in adults are controversial. Moreover, genetic defects of complement regulation have been recently described in children with STEC-HUS, thus challenging the current HUS classification. The identification of a role of complement genes abnormalities in these patients could have important clinical implications for diagnosis and treatment. In this study, we assessed the presence of complement genes abnormalities in children with secondary HUS. Method We describe a case series of pediatric patients diagnosed with secondary HUS. All patients were screened for the presence of ADAMTS13 auto-antibody and ADAMTS13 deficiency. We performed next-generation sequencing for a panel of complement genes reported in association with aHUS (CFH, CFI, MCP, C3, FB, and THBD). Copy number variations and hybrid genes assessment were included in the analysis. Results Four patients aged 1-4 years with a diagnosis of sporadic secondary HUS were included in the study. HUS was secondary to glomerulopathy, cobalamin deficiency, bone marrow transplantation, and pneumococcal pneumoniae. Two out of four patients showed hypocomplementaemia (both C3 and C4). Diarrhea was a common clinical feature in all patients at onset, and none of these patients showed neurologic involvement. Renal replacement therapy was required in two patients at onset. Only one patient did not recover kidney function, and subsequently underwent kidney transplantation. Next-generation sequencing showed genetic abnormalities in all the patients (Table 1). All but one genetic variants have already been described in association with atypical HUS. Interestingly, haplotypes in CHF and MCP were present in three patients, all of Caucasian ethnicity. Conclusion According to the current HUS classification, complement abnormalities are diagnostic of aHUS. However, results coming from pediatric cohorts of STEC-HUS patients already claimed a role for genetic background also outside the aHUS spectrum, suggesting that the current terminology lacks both specificity and suggestion of cause. In this case series, complement genes abnormalities were present in all patients. Whether confirmed in larger cohorts, these findings would support the role of genetic background even in secondary HUS, suggesting the need for a revision of the current HUS classification, in agreement with the pathogenic mechanisms, in order to tailor the optimal treatment.

Complement inhibitors are not useful in secondary hemolytic uremic syndromes

Complement inhibitors are not useful in secondary hemolytic uremic syndromes

Complement inhibitors are useful in secondary hemolytic uremic syndromes

Complement inhibitors are useful in secondary hemolytic uremic syndromes

Secondary atypical hemolytic uremic syndromes in the era of complement blockade

Le Clech etal. found rare variants in complement genes in only 5% of patients among a large cohort of secondary hemolytic uremic syndrome cases. The absence of genetic abnormalities does not exclude, however, the implication of complement in the pathogenesis of secondary hemolytic uremic syndrome. Prospective studies should be performed to evaluate the efficacy of complement blockers in patients with secondary atypical hemolytic uremic syndrome who do not respond to the treatment of the triggering condition.

Atypical and secondary hemolytic uremic syndromes have a distinct presentation and no common genetic risk factors

Secondary hemolytic uremic syndrome (HUS) is a heterogeneous group of thrombotic microangiopathies associated with various underlying conditions. Whether it belongs to the spectrum of complement-mediated HUS remains controversial. We analysed the presentation, outcome, and frequency of complement gene rare variants in a cohort of 110 patients with secondary HUS attributed to drugs (29%), autoimmune diseases (24%), infections (17%), malignancies (10%), glomerulopathies (9%), extra-renal organ transplantation (8%), and pancreatitis (3%). The frequency of complement gene rare variants was similar in patients with secondary HUS (5%) and in healthy individuals (6% and 8% in French and European controls, respectively). At diagnosis, 40% of patients required dialysis and 18% had neurological manifestations. Fifty percent of patients received plasmatherapy and 35% were treated with eculizumab. Haematological and complete renal remission was achieved in 80% and 24% of patients, respectively. Thirty-nine percent of patients progressed to chronic kidney disease (stages 3-4) and an additional 37% reached end-stage renal disease. Eleven percent of patients died, most often from complications of the underlying cause of HUS. Only one patient experienced an HUS relapse. Patients treated with eculizumab presented with more severe HUS and were more likely to require dialysis at the time of diagnosis as compared to patients not treated with eculizumab. Rates of hematological remission, chronic kidney disease (stages 3-4), and end-stage renal disease were similar in the two groups. Secondary HUS is an acute nonrelapsing form of HUS, not related to complement dysregulation. The efficacy of eculizumab in this setting is not yet established.

The Role of Complement in the Pathogenesis of HUS and the TMA Spectrum Disorders

This review aims to examine the current definitions of primary and secondary hemolytic uremic syndromes. Specifically, it seeks to determine which external conditions can result in secondary Thrombotic microangiopathy (TMA), which can trigger cases of primary atypical uremic syndromes (aHUS), and the role of complement in the pathogenesis of TMA spectrum disorders. Building on the growing insight about the pathogenic role of dysregulation of the alternative complement pathway in primary aHUS, the successful use of complement-blocking treatment in cases of thrombotic microangiopathy with coexisting conditions (secondary TMA), along with the identification of complement mutations in some of these cases, indicates a so far possibly under-appreciated pathogenic role for complement in diagnoses within the TMA spectrum. Uncontrolled complement activity and pro-thrombotic environments represent a unifying pathogenic mechanism in aHUS and the TMA spectrum disorders and point towards shared diagnostic and therapeutic pathways.

Case report - atypical hemolytic uremic syndrome triggered by influenza B

BackgroundInfluenza A infections have been described to cause secondary hemolytic uremic syndrome and to trigger atypical hemolytic uremic syndrome (aHUS) in individuals with an underlying genetic complement dysregulation. To date, influenza B has not been reported to trigger aHUS.Case presentationA 6-month-old boy presented with hemolytic uremic syndrome triggered by influenza B infection. Initially the child recovered spontaneously. When he relapsed Eculizumab treatment was initiated, resulting in complete and sustained remission. A pathogenic mutation in membrane cofactor protein (MCP) was detected.ConclusionInfluenza B is a trigger for aHUS and might be underreported as such. Influenza vaccination may protect patients at risk.

The case of successful therapy with rituximab secondary hemolytic-uremic syndrome in a patient after the second allogeneic hematopoietic stem cell transplantation

Transplant-associated thrombotic microangiopathy (TA-TMA) is rare but very unfavour multifactorial complication of allogenic hematopoietic stem cell transplantation (HSCT). Diagnostics of TA-TMA complicated by non-specificity of clinical signs and histological picture, as well as its frequent appearance in the background of other complications of HSCT. Currently there are no clear recommendations for TA-TMA treatment. This clinical case demonstrates manifestation of TA-TMA as hemolytic-uremic syndrome at the patient in 4th remission of acute lymphoblastic leukemia on the early stages after the second allogenic HSCT. Possibility of successful rituximab therapy with condition stabilization and TA-TMA resolving demonstrated.

Primary and Secondary Thrombotic Microangiopathy Referred to a Single Plasma Exchange Center for Suspected Thrombotic Thrombocytopenic Purpura: 2000-2011

Background: Patients who present with unexplained thrombocytopenia, that is, hemolytic anemia with end-organ dysfunction with a normal coagulation profile are suspected to have thrombotic thrombocytopenic purpura (TTP) and are usually referred to a plasma exchange (PE) center for immediate treatment to prevent mortality. Here, we describe the distribution and outcomes of patients with suspected TTP referred to a single center for PE therapy. Methods: In this retrospective cohort study, we reviewed the data of all consecutive patients who were treated with PE for suspected TTP at our center between January 2000 and December 2011 (Canada). Patients were followed for a median of 73 months. Results: Of 137 patients, 70 (51%) were determined to have primary (idiopathic) TTP and 67 (49%) secondary TTP or hemolytic uremic syndrome (HUS). Patients with primary TTP were twice as likely to be refractory than those with secondary TTP or HUS: 27 vs. 12%; p = 0.03. Patients with primary TTP were more likely to experience remission (61/70 (87%) vs. 45/67 (67%); p = 0.01); however, the relapse rate was higher in patients with primary versus secondary TTP-HUS: 11 vs. 1.5%, respectively (p = 0.03). The overall mortality rate was 23% (13 vs. 33% in those with primary vs. secondary TTP-HUS; p = 0.007). After excluding deaths from scleroderma renal crisis (100% mortality), malignancy (75% mortality) and stem cell transplant (50% mortality), the survival rate for secondary TTP was 85%. Conclusions: In contrast to patients with secondary TTP or HUS, those with primary TTP have a higher refractory and relapse rate, but are also more likely to achieve remission and survive.

Secondary thrombotic microangiopathy in two patients with Philadelphia-positive hematological malignancies treated with imatinib mesylate

Drug-mediated thrombotic microangiopathy may cause life-threatening medical emergencies. Novel targeted therapies have dramatically changed the prognosis of a number of oncological diseases. Tyrosine kinase inhibitors of the Breakpoint Cluster Region-Abelson (BCR-ABL) oncoprotein are used in patients with chronic myeloid leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia. Imatinib mesylate, which was the first anti-BCR-ABL tyrosine kinase inhibitor, has demonstrated a high tolerance profile and efficacy in these patients for many years. Good results have also been observed in patients with gastrointestinal stromal tumors. In this study, we describe two patients with Philadelphia chromosome-positive hematological malignancies who presented with secondary thrombotic microangiopathy that was most likely linked to the use of imatinib. Other potential causes of thrombotic microangiopathy were discarded, and the predisposing role of some comorbidities and potential short or long-term drug-drug interactions was assessed. The clinical and biological data were more indicative of atypical secondary hemolytic uremic syndrome in one of the cases and of secondary thrombotic microangiopathy with renal and cardiac impairment in the other, which is also categorized as secondary hemolytic uremic syndrome. The outcome was favorable after imatinib discontinuation and the treatment of severe cardiac and renal failures.

Update on hemolytic uremic syndrome: Diagnostic and therapeutic recommendations

Hemolytic uremic syndrome (HUS) is a rare disease. In this work the authors review the recent findings on HUS, considering the different etiologic and pathogenetic classifications. New findings in genetics and, in particular, mutations of genes that encode the complement-regulatory proteins have improved our understanding of atypical HUS. Similarly, the complement proteins are clearly involved in all types of thrombotic microangiopathy: typical HUS, atypical HUS and thrombotic thrombocytopenic purpura (TTP). Furthermore, several secondary HUS appear to be related to abnormalities in complement genes in predisposed patients. The authors highlight the therapeutic aspects of this rare disease, examining both "traditional therapy" (including plasma therapy, kidney and kidney-liver transplantation) and "new therapies". The latter include anti-Shiga-toxin antibodies and anti-C5 monoclonal antibody "eculizumab". Eculizumab has been recently launched for the treatment of the atypical HUS, but it appears to be effective in the treatment of typical HUS and in TTP. Future therapies are in phases I and II. They include anti-C5 antibodies, which are more purified, less immunogenic and absorbed orally and, anti-C3 antibodies, which are more powerful, but potentially less safe. Additionally, infusions of recombinant complement-regulatory proteins are a potential future therapy.

Ciprofloxacin-Associated Hemolytic-Uremic Syndrome

OBJECTIVE:To report the first case of ciprofloxacin-associated hemolytic-uremic syndrome (HUS).CASE SUMMARY:A 53-year-old white man was treated with chemotherapy for acute lymphoblastic leukemia. Four weeks after initiation of treatment, he recovered his blood cell counts, but developed fever and was prescribed oral ciprofloxacin 500 mg twice daily. After 4 doses, he developed the typical features of HUS manifested by microangiopathic hemolytic anemia, oliguric renal failure, and thrombocytopenia. The medication was withdrawn, and he received 5 sessions of plasma exchange. He recovered completely and has normal renal function.DISCUSSION:Secondary HUS or its related syndrome, thrombotic thrombocytopenic purpura (TTP), is uncommon, but has been reported in association with cancer, chemotherapy, and a variety of medications. Our case represents a possible adverse drug reaction to ciprofloxacin according to the Naranjo probability scale. It is the first reported case of HUS associated with ciprofloxacin.CONCLUSIONS:Ciprofloxacin use was followed by HUS in our patient and was possibly causally related. Early detection, discontinuation of the offending medication, and treatment of HUS/TTP is critical.

Hemolytic Uremic Syndrome Associated With Glomerular Disease

Secondary hemolytic uremic syndrome (HUS) is uncommon. When it occurs, it is usually in association with pregnancy, malignancy, severe hypertension, drugs, or collagen vascular diseases. It has rarely been reported in patients with glomerular disease. Two such patients with secondary HUS are described. A 17-month-old girl with hematuria and the nephrotic syndrome, negative antistreptolycin O (ASO) titer, and low serum levels of C3 and C4 developed oliguria, progressive azotemia, thrombocytopenia, and microangiopathic hemolytic anemia. A kidney biopsy showed fibrin in glomerular capillaries and cresentic membranoproliferative glomerulonephritis. A 22-year-old man with a 16-year history of relapsing minimal change nephrotic syndrome had been in remission for 5 years when he experienced nephrotic syndrome relapse and developed thrombocytopenia, microangiopathic hemolytic anemia, and renal failure. A kidney biopsy revealed foot process fusion and obstruction of glomerular capillaries with fibrin and platelets. These cases illustrate that HUS can occur in association with other glomerular diseases and should be considered when thrombocytopenia and hemolytic anemia occur in a nephritic or nephrotic patient.