COVID-19 as a potential trigger of complement-mediated atypical HUS

Thrombotic Microangiopathy Post-COVID-19 Vaccination

The emergence of COVID-19 has caused a wide spectrum of symptoms, ranging from asymptomatic to devastating symptoms, leading to death. One of the most serious complications of COVID-19 is the thromboembolic phenomenon, which has led to increased morbidity and mortality. Several vaccines were developed to protect against this infection and used widely across the globe. However, thromboembolic events were observed in the vaccinated population and were certainly the most commonly reported events following the COVID-19 vaccination. Although the thrombotic complications of COVID-19 were poorly understood, hyper-inflammatory responses were thought to be one of the main explanations for this infection sequel. In the setting of COVID-19 vaccines, there is still no clear understanding of the thrombosis pathophysiology, and, again, exaggerated pro-inflammatory and immune-mediated processes seem to be leading causes. Definitely, with the rise in reported cases of serious complications and increased awareness of these phenomena, we learn new theories and explanations that help us understand and manage those patients. We report the case report of two patients we managed over the last three years who presented with thrombotic microangiopathy following the COVID-19 vaccination.

Coronavirus disease 2019-associated thrombotic microangiopathy treated with plasma exchange and antihypertensive therapy in a patient with HIV: A case report with literature review

RATIONALE

Coronavirus disease 2019 (COVID-19) is an infectious disease that often causes complications in multiple organs and thrombosis due to abnormal blood coagulation. This case report aimed to describe the clinical course of COVID-19-associated thrombotic microangiopathy (TMA) and reviewed the comprehensive information on TMA, thrombotic thrombocytopenic purpura (TTP), and atypical hemolytic uremic syndrome associated with COVID-19 in the past literature.

PATIENT CONCERNS

A 46-year-old Japanese man was diagnosed with human immunodeficiency virus infection 10 years ago and treated with antiretroviral therapy. The patient presented with fever, malaise, hematuria, and bilateral upper abdominal discomfort for the past 4 days.

DIAGNOSES

COVID-19-associated TMA was diagnosed based on a positive polymerase chain reaction for severe acute respiratory syndrome coronavirus 2 and laboratory findings such as thrombocytopenia, acute kidney injury, and hemolytic anemia. Malignant hypertension and human immunodeficiency virus infection were also considered as differential diagnoses of TMA.

INTERVENTIONS

Considering the possibility of TTP, plasma exchange was performed, and glucocorticoids were administered. Hemodialysis was performed for acute kidney injury. Antihypertensive drugs were administered to control the high blood pressure.

OUTCOMES

Platelet count and renal function improved, and hemodialysis was no longer required. The patient was in good general condition and was discharged from the hospital.

LESSONS

COVID-19-associated TMA should be considered as a differential diagnosis during the COVID-19 epidemic. Excessive inflammation and severe COVID-19 are not essential for TMA development. Early intervention using conventional TMA treatments, such as plasma exchange and corticosteroids, might be important in improving prognosis while differentiating between TTP and atypical hemolytic uremic syndrome. Antihypertensive therapy may be helpful in the treatment of COVID-19-associated TMA.

Immune responses and safety of COVID-19 vaccination in atypical hemolytic uremic syndrome patients in Taiwan

Atypical hemolytic uremic syndrome is a rare, life-threatening disorder which can be triggered by COVID 19 infection and COVID 19 vaccination then induce multiple organ failure. Our study is the first to evaluate immune responses to COVID-19 vaccination and safety in a cohort of patients in a local single-center study in Taiwan.. Results indicate that vaccines effectively shield aHUS patients from severe COVID-19 complications without significant safety concerns. A double booster dose for the third vaccine is essential for optimal efficacy. Anti-complement therapy did not influence vaccination effectiveness. Transplant aHUS patients had the lowest immune response titers, indicating a need for additional vaccine doses. Compared to healthcare workers, aHUS patients had poor T-cell responses. We noted a superior trend with mixed-type COVID-19 vaccinations in aHUS patients, while fixed-type mRNA demonstrated better results in healthcare workers. Our findings endorse COVID-19 vaccination as a potent strategy to safeguard aHUS patients from severe complications, emphasizing the importance of vigilant monitoring pre- and post-vaccination.

Complement-Mediated Thrombotic Microangiopathy Related to COVID-19 or SARS-CoV-2 Vaccination

Introduction

Infectious diseases and vaccinations are trigger factors for thrombotic microangiopathy. Consequently, the COVID-19 pandemic could have an effect on disease manifestation or relapse in patients with atypical hemolytic syndrome/complement-mediated thrombotic microangiopathy (aHUS/cTMA).

Methods

We employed the Vienna TMA cohort database to examine the incidence of COVID-19 related and of SARS-CoV-2 vaccination-related relapse of aHUS/cTMA among patients previously diagnosed with aHUS/cTMA during the first 2.5 years of the COVID-19 pandemic. We calculated incidence rates, including respective confidence intervals (CIs) and used Cox proportional hazard models for comparison of aHUS/cTMA episodes following infection or vaccination.

Results

Among 27 patients with aHUS/cTMA, 13 infections triggered 3 (23%) TMA episodes, whereas 70 vaccinations triggered 1 TMA episode (1%; odds ratio 0.04; 95% CI 0.003-0.37, P = 0.01). In total, the incidence of TMA after COVID-19 or SARS-CoV-2 vaccination was 6 cases per 100 patient years (95% CI 0.017-0.164) (4.5/100 patient years for COVID-19 and 1.5/100 patient years for SARS-CoV-2 vaccination). The mean follow-up time was 2.31 ± 0.26 years (total amount: 22,118 days; 62.5 years) to either the end of the follow-up or TMA relapse (outcome). Between 2012 and 2022 we did not find a significant increase in the incidence of aHUS/cTMA.

Conclusion

COVID-19 is associated with a higher risk for aHUS/cTMA recurrence when compared to SARS-CoV-2 vaccination. Overall, the incidence of aHUS/cTMA after COVID-19 infection or SARS-CoV-2 vaccination is low and comparable to that described in the literature.

How I diagnose and treat atypical hemolytic uremic syndrome

Our understanding and management of atypical hemolytic uremic syndrome (aHUS) have dramatically improved in the last decade. aHUS has been established as a prototypic disease resulting from a dysregulation of the complement alternative C3 convertase. Subsequently, prospective nonrandomized studies and retrospective series have shown the efficacy of C5 blockade in the treatment of this devastating disease. C5 blockade has become the cornerstone of the treatment of aHUS. This therapeutic breakthrough has been dulled by persistent difficulties in the positive diagnosis of aHUS, and the latter remains, to date, a diagnosis by exclusion. Furthermore, the precise spectrum of complement-mediated renal thrombotic microangiopathy is still a matter of debate. Nevertheless, long-term management of aHUS is increasingly individualized and lifelong C5 blockade is no longer a paradigm that applies to all patients with this disease. The potential benefit of complement blockade in other forms of HUS, notably secondary HUS, remains uncertain.

COVID-19 vaccination and Atypical hemolytic uremic syndrome

Introduction

COVID-19 vaccination has been associated with rare but severe complications characterized by thrombosis and thrombocytopenia.

Methods and Results

Here we present three patients who developed de novo or relapse atypical hemolytic uremic syndrome (aHUS) in native kidneys, a median of 3 days (range 2-15) after mRNA-based (Pfizer/BioNTech's, BNT162b2) or adenoviral (AstraZeneca, ChAdOx1 nCoV-19) COVID-19 vaccination. All three patients presented with evident hematological signs of TMA and AKI, and other aHUS triggering or explanatory events were absent. After eculizumab treatment, kidney function fully recovered in 2/3 patients. In addition, we describe two patients with dubious aHUS relapse after COVID-19 vaccination. To assess the risks of vaccination, we retrospectively evaluated 29 aHUS patients (n=8 with native kidneys) without complement-inhibitory treatment, who received a total of 73 COVID-19 vaccinations. None developed aHUS relapse after vaccination.

Conclusion

In conclusion, aHUS should be included in the differential diagnosis of patients with vaccine-induced thrombocytopenia, especially if co-occuring with mechanical hemolytic anemia (MAHA) and acute kidney injury (AKI). Still, the overall risk is limited and we clearly advise continuation of COVID-19 vaccination in patients with a previous episode of aHUS, yet conditional upon clear patient instruction on how to recognize symptoms of recurrence. At last, we suggest monitoring serum creatinine (sCr), proteinuria, MAHA parameters, and blood pressure days after vaccination.

Coronavirus Disease 2019 (COVID-19) Associated Hemolytic Uremic Syndrome in a Toddler

Coronavirus disease 2019 (COVID-19) is a heterogenous, predominantly pulmonary disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that has resulted in catastrophic illness around the world. Thrombotic microangiopathy (TMA) is a triad of hemolytic anemia, thrombocytopenia, and end organ damage. This is present in severe cases of COVID-19 and in hemolytic uremic syndrome (HUS) commonly caused by Escherichia coli (E.coli) 0157:H7. We report a novel case of a toddler who presented with classic features suggestive of HUS characterized by bloody diarrhea followed by thrombocytopenia, hemolytic anemia, and acute kidney injury, in whom a polymerase chain reaction (PCR) test for SARS-CoV-2 was positive.

Epidemiology and outcomes of pediatric transplant-associated thrombotic microangiopathy in Hong Kong

BACKGROUND

Transplant-associated thrombotic microangiopathy (TA-TMA) is an under-recognized yet potentially devastating complication of hematopoietic stem cell transplantation (HSCT) which had increased awareness in recent years. This report summarizes the demographics and outcomes of pediatric TA-TMA in Hong Kong.

METHODS

All patients aged below 18 years who underwent HSCT in the Hong Kong Children's Hospital and were diagnosed to have TA-TMA during the 2-year period from April 1, 2019 to March 31, 2021 were included.

RESULTS

A total of 73 transplants (51 allogeneic and 22 autologous) in 63 patients had been performed. Six patients (four males and two females) developed TA-TMA at a median duration of 2.5 months post-HSCT. The incidence rate was 9.52%. Of the six TA-TMA patients, five underwent allogenic one underwent autologous HSCT, respectively. Three of them were histologically proven. All four patients with cyclosporine had stopped the drug once TA-TMA was suspected. Median six doses of eculizumab were administered to five out of six patients. Three patients died (two due to fungal infection and one due to acute-on-chronic renal failure) within 3 months upon diagnosis of TA-TMA. Among three survivors, two stabilized with mild stage 2 chronic kidney disease (CKD) while the other suffered from stage 5 end-stage CKD requiring lifelong dialysis.

CONCLUSION

In conclusion, recognition and diagnosis of TA-TMA are challenging. Early recognition and prompt administration of complement blockage with eculizumab may be beneficial in selected cases. Further prospective research studies are recommended to improve the management and outcomes of TA-TMA.

Coronavirus Disease 2019-Associated Thrombotic Microangiopathy: Literature Review

Coronavirus disease 2019 (COVID-19) can lead to clinically significant multisystem disorders that also affect the kidney. According to recent data, renal injury in the form of thrombotic microangiopathy (TMA) in native kidneys ranks third in frequency. Our review of global literature revealed 46 cases of TMA in association with COVID-19. Among identified cases, 18 patients presented as thrombotic thrombocytopenic purpura (TTP) and 28 cases presented as atypical hemolytic uremic syndrome (aHUS). Altogether, seven patients with aHUS had previously proven pathogenic or likely pathogenic genetic complement abnormalities. TMA occurred at the time of viremia or even after viral clearance. Infection with COVID-19 resulted in almost no or only mild respiratory symptoms in the majority of patients, while digestive symptoms occurred in almost one-third of patients. Regarding the clinical presentation of COVID-19-associated TMA, the cases showed no major deviations from the known presentation. Patients with TTP were treated with plasma exchange (88.9%) or fresh frozen plasma (11.1%), corticosteroids (88.9%), rituximab (38.9%), and caplacizumab (11.1%). Furthermore, 53.6% of patients with aHUS underwent plasma exchange with or without steroid as initial therapy, and 57.1% of patients received a C5 complement inhibitor. Mortality in the studied cohort was 16.7% for patients with TTP and 10.7% for patients with aHUS. The exact role of COVID-19 in the setting of COVID-19-associated TMA remains unclear. COVID-19 likely represents a second hit of aHUS or TTP that manifests in genetically predisposed individuals. Early identification of the TMA subtype and appropriate prompt and specific treatment could lead to good outcomes comparable to survival and recovery statistics for TMA of all causes.

Diagnosis and treatment of thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is characterized by thrombocytopenia, microangiopathic haemolytic anaemia and end organ damage. TMAs have varying underlying pathophysiology and can therefore present with an array of clinical presentations. Renal involvement is common as the kidney is particularly susceptible to the endothelial damage and microvascular occlusion. TMAs require rapid assessment, diagnosis, and commencement of appropriate treatment due to the high morbidity and mortality associated with them. Ground-breaking research into the pathogenesis of TMAs over the past 20 years has driven the successful development of targeted therapeutics revolutionizing patient outcomes. This review outlines the clinical presentations, pathogenesis, diagnostic tests and treatments for TMAs.

COVID-19: A Rare Cause of Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is a multisystemic condition characterized by a triad of acute renal failure, microangiopathic hemolytic anemia, and thrombocytopenia. HUS can be classified as atypical or typical, depending upon its association with the Shiga toxin-producing Escherichia coli (STEC). Approximately 90-95% of cases are classified as typical, while only 5-10% of cases are atypical. The pathogenesis of atypical HUS (aHUS) occurs when the complement cascade is activated and causes membrane attack complex (MAC) deposition in the renal tubular epithelium. Various infectious triggers have been associated with aHUS. A new and compelling correlation to this rare and potentially deadly diagnosis of aHUS is COVID-19 infection or vaccination. We present a case of COVID-19-induced exacerbation of a patient with a known history of aHUS. In addition, we performed a literature review of previously reported COVID-19-induced aHUS cases and identified the potential pathogenesis of the disease state.

Complement-mediated microvascular injury and thrombosis in the pathogenesis of severe COVID-19: A review

Coronavirus disease 2019 (COVID-19) causes acute microvascular thrombosis in both venous and arterial structures which is highly associated with increased mortality. The mechanisms leading to thromboembolism are still under investigation. Current evidence suggests that excessive complement activation with severe amplification of the inflammatory response (cytokine storm) hastens disease progression and initiates complement-dependent cytotoxic tissue damage with resultant prothrombotic complications. The concept of thromboinflammation, involving overt inflammation and activation of the coagulation cascade causing thrombotic microangiopathy and end-organ damage, has emerged as one of the core components of COVID-19 pathogenesis. The complement system is a major mediator of the innate immune response and inflammation and thus an appealing treatment target. In this review, we discuss the role of complement in the development of thrombotic microangiopathy and summarize the current data on complement inhibitors as COVID-19 therapeutics.

COVID-19 microthrombosis: unusually large VWF multimers are a platform for activation of the alternative complement pathway under cytokine storm

ADAMTS13, a metalloproteinase, specifically cleaves unusually large multimers of von Willebrand factor (VWF), newly released from vascular endothelial cells. The ratio of ADAMTS13 activity to VWF antigen (ADAMTS13/VWF) and indicators of the alternative complement pathway (C3a and sC5b-9) are both related to the severity of COVID-19. The ADAMTS13/VWF ratio is generally moderately decreased (0.18–0.35) in patients with severe COVID-19. When these patients experience cytokine storms, both interleukin-8 and TNFα stimulate VWF release from vascular endothelial cells, while interleukin-6 inhibits both production of ADAMTS13 and its interaction with VWF, resulting in localized severe deficiency of ADAMTS13 activity. Platelet factor 4 and thrombospondin-1, both released upon platelet activation, bind to the VWF-A2 domain and enhance the blockade of ADAMTS13 function. Thus, the released unusually-large VWF multimers remain associated with the vascular endothelial cell surface, via anchoring with syndecan-1 in the glycocalyx. Unfolding of the VWF-A2 domain, which has high sequence homology with complement factor B, allows the domain to bind to activated complement C3b, providing a platform for complement activation of the alternative pathway. The resultant C3a and C5a generate tissue factor-rich neutrophil extracellular traps (NETs), which induce the mixed immunothrombosis, fibrin clots and platelet aggregates typically seen in patients with severe COVID-19.

Case Report: Tackling Complement Hyperactivation With Eculizumab in Atypical Hemolytic Uremic Syndrome Triggered by COVID-19

Hemolytic uremic syndrome (HUS) is a rare life-threatening disease of unrestrained complement system dysregulation, microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure in genetically predisposed individuals. In this report, we describe two cases of SARS-CoV-2–associated HUS treated with eculizumab, a C5-blocking monoclonal antibody reported to be remarkably effective in the treatment of HUS. Detailed biochemical and genetic complement system analysis is reported, and the prompt clinical response after C5 pharmacological blockade is documented. Our report provides the rationale and supports the use of terminal complement pathway inhibition for the treatment of SARS-CoV-2–associated HUS.

Anti-factor H antibody associated hemolytic uremic syndrome following SARS-CoV-2 infection

BACKGROUND

The pathogenesis of autoantibody generation in anti-factor H (FH) antibody associated atypical hemolytic uremic syndrome (aHUS) is unknown and is perhaps triggered by an infectious or environmental agent. We observed an unusual increase of patients with anti-FH antibody associated aHUS coinciding with the second pandemic wave in New Delhi and suspected that SARS-CoV-2 infection might be a potential trigger.

METHODS

We screened for SARS-CoV-2 infection using reverse transcriptase polymerase chain reaction (RT-PCR) and serology in 13 consecutive patients with anti-FH antibody associated aHUS during the past year in New Delhi.

RESULTS

We report 5 patients, 4-13 years old, who presented with a febrile illness without respiratory symptoms during the second pandemic wave. Of these, 3 patients presented with a relapse 25-85 months following the initial episode of aHUS. SARS-CoV-2 was detected by RT-PCR in 1 patient and by serology in 4 patients (median titer 47.1 cut-off index). Patients had high titers of anti-FH antibodies (median 2,300 AU/ml). Genetic studies, done in 3 of the 5 patients, showed homozygous CFHR1 deletion without other significant genetic abnormalities. Specific management comprised plasma exchanges and oral prednisolone, combined with either cyclophosphamide or mycophenolate mofetil. At median follow-up of 3.3 months, the estimated glomerular filtration rate in 4 patients ranged from 62 to 110 ml/min/1.73 m²; one patient was dialysis-dependent.

CONCLUSION

Increased vigilance is required during the pandemic, especially in patients with anti-FH associated aHUS, who might relapse despite quiescent disease for a prolonged period. A higher resolution version of the Graphical abstract is available as Supplementary information.

Complement Mediated Hemolytic Anemias in the COVID-19 Era: Case Series and Review of the Literature

The complex pathophysiologic interplay between SARS-CoV-2 infection and complement activation is the subject of active investigation. It is clinically mirrored by the occurrence of exacerbations of complement mediated diseases during COVID-19 infection. These include complement-mediated hemolytic anemias such as paroxysmal nocturnal hemoglobinuria (PNH), autoimmune hemolytic anemia (AIHA), particularly cold agglutinin disease (CAD), and hemolytic uremic syndrome (HUS). All these conditions may benefit from complement inhibitors that are also under study for COVID-19 disease. Hemolytic exacerbations in these conditions may occur upon several triggers including infections and vaccines and may require transfusions, treatment with complement inhibitors and/or immunosuppressors (i.e., steroids and rituximab for AIHA), and result in thrombotic complications. In this manuscript we describe four patients (2 with PNH and 2 with CAD) who experienced hemolytic flares after either COVID-19 infection or SARS-Cov2 vaccine and provide a review of the most recent literature. We report that most episodes occurred within the first 10 days after COVID-19 infection/vaccination and suggest laboratory monitoring (Hb and LDH levels) in that period. Moreover, in our experience and in the literature, hemolytic exacerbations occurring during COVID-19 infection were more severe, required greater therapeutic intervention, and carried more complications including fatalities, as compared to those developing after SARS-CoV-2 vaccine, suggesting the importance of vaccinating this patient population. Patient education remains pivotal to promptly recognize signs/symptoms of hemolytic flares and to refer to medical attention. Treatment choice should be based on the severity of the hemolytic exacerbation as well as of that of COVID-19 infection. Therapies include transfusions, complement inhibitor initiation/additional dose in the case of PNH, steroids/rituximab in patients with CAD and warm type AIHA, plasma exchange, hemodialysis and complement inhibitor in the case of atypical HUS. Finally, anti-thrombotic prophylaxis should be always considered in these settings, provided safe platelet counts.