Thrombotic microangiopathies assessment: mind the complement

Eculizumab for Shiga-toxin-induced hemolytic uremic syndrome in adults with neurological involvement

The role of eculizumab in treating Shiga-toxin-producing Escherichia coli (STEC) hemolytic uremic syndrome (HUS) patients with neurological involvement remains unclear. We describe two distinctly different STEC-HUS patients with neurologic involvement successfully managed with eculizumab, and perform a literature review of all published cases. Both patients had complete resolution of neurological symptoms after initiation of eculizumab. Eighty patients with STEC-HUS treated with eculizumab were identified in the literature, 68.7% had complete resolution of neurological symptoms. Based on our experience and literature review, three prevailing themes were noted: 1) Early eculizumab administration optimized neurological outcomes, 2) Symptom resolution may not be immediate, neurological symptoms may initially worsen before improvement, and 3) Plasma exchange yielded no benefit. Early administration of eculizumab may reverse neurotoxicity in patients with STEC-HUS.

Clinical Evaluation and Management of Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) refers to a diverse group of diseases that share clinical and histopathologic features. TMA is clinically characterized by microangiopathic hemolytic anemia, consumptive thrombocytopenia, and organ injury that stems from endothelial damage and vascular occlusion. There are several disease states with distinct pathophysiological mechanisms that manifest as TMA. These conditions are associated with significant morbidity and mortality and require urgent recognition and treatment. Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome are traditionally considered to be primary forms of TMA, but TMA more commonly occurs in association with a coexisting condition such as infection, pregnancy, autoimmune disease, or malignant hypertension, among others. Determining the cause of TMA is a diagnostic challenge because of limited availability of disease-specific testing. However, identifying the underlying etiology is imperative as treatment strategies differ. Our understanding of the conditions that cause TMA is evolving. Recent advances have led to improved comprehension of the varying pathogenic mechanisms that drive TMA. Development of targeted therapeutics has resulted in significant improvements in patient outcomes. In this article, we review the pathogenesis and clinical features of the different TMA-causing conditions. We outline a practical approach to diagnosis and management and discuss empiric and disease-specific treatment strategies.

Endothelial activation and damage as a common pathological substrate in different pathologies and cell therapy complications

The endothelium is a biologically active interface with multiple functions, some of them common throughout the vascular tree, and others that depend on its anatomical location. Endothelial cells are continually exposed to cellular and humoral factors, and to all those elements (biological, chemical, or hemodynamic) that circulate in blood at a certain time. It can adapt to different stimuli but this capability may be lost if the stimuli are strong enough and/or persistent in time. If the endothelium loses its adaptability it may become dysfunctional, becoming a potential real danger to the host. Endothelial dysfunction is present in multiple clinical conditions, such as chronic kidney disease, obesity, major depression, pregnancy-related complications, septic syndromes, COVID-19, and thrombotic microangiopathies, among other pathologies, but also in association with cell therapies, such as hematopoietic stem cell transplantation and treatment with chimeric antigen receptor T cells. In these diverse conditions, evidence suggests that the presence and severity of endothelial dysfunction correlate with the severity of the associated disease. More importantly, endothelial dysfunction has a strong diagnostic and prognostic value for the development of critical complications that, although may differ according to the underlying disease, have a vascular background in common. Our multidisciplinary team of women has devoted many years to exploring the role of the endothelium in association with the mentioned diseases and conditions. Our research group has characterized some of the mechanisms and also proposed biomarkers of endothelial damage. A better knowledge would provide therapeutic strategies either to prevent or to treat endothelial dysfunction.

Thrombotic Microangiopathy and Multiple Organ Failure in Scleroderma Renal Crisis: A Case Report

This case report can be considered a rare occurrence of scleroderma renal crisis (SRC) presenting with a severe clinical course and multiple organ failure. A patient diagnosed with systemic sclerosis four years earlier was admitted to the hospital because of severe malignant systolic-diastolic arterial hypertension and acute kidney injury (AKI). Exacerbating disease suggested thrombotic microangiopathy (TMA) and the PLASMIC (Platelet count; combined hemoLysis variable; absence of Active cancer; absence of Stem-cell or solid-organ transplant; MCV; INR; Creatinine) score was used in the differential diagnosis. Despite the timely initiation of therapy with ACE inhibitors (ACE-I), the progressive renal failure required hemodialysis treatment, but renal function never recovered. Disease duration, skin involvement, and previous specific pharmacological therapy represented multiple risk factors that determined a clinical course complicated by pericardial tamponade with acute heart failure, acute pancreatitis, and ischemic stroke, with fatal evolution. These complications presented a challenging clinical sequence of events requiring an interdisciplinary course of action. Timely ascertainment of the SRC is important given the possible severe organ involvement as well as mortality. A diagnosis of scleroderma renal crisis should be considered in cases of acute kidney injury associated with known risk factors. Early treatment and collaboration between rheumatology and renal physicians can improve patient outcomes.

Hematopoietic stem cell transplantation-associated thrombotic microangiopathy and the role of advanced practice providers and pharmacists

Hematopoietic stem cell transplantation-associated thrombotic microangiopathy (HSCT-TMA) is a severe and potentially life-threatening complication. HSCT-TMA is often underdiagnosed due to multifactorial pathophysiology and a historic lack of standard diagnostic criteria. Identification of the multi-hit hypothesis and the key role of the complement system, particularly the lectin pathway of complement, has led to development of treatments targeting the underlying pathogenesis of HSCT-TMA. Additional research is ongoing to investigate the efficacy and safety of these targeted therapies in patients with HSCT-TMA. Advanced practice providers (APPs; nurse practitioners and physician assistants) and pharmacists are critical members of the multidisciplinary HSCT team and ensure management of patients throughout the continuum of care. Additionally, pharmacists and APPs can improve patient care through medication management of complex regimens; transplant education for patients, staff, and trainees; evidence-based protocol and clinical guideline development; assessment and reporting of transplant-related outcomes; and quality improvement initiatives to improve outcomes. Understanding the presentation, prognosis, pathophysiology, and treatment options for HSCT-TMA can improve each of these efforts. Collaborative practice model for monitoring and care of HSCT-TMA. Advanced practice providers and pharmacists contribute to many aspects of patient care in transplant centers, including medication management for complex regimens; transplant education for patients, staff, and trainees; evidence-based protocol and clinical guideline development; assessment and reporting of transplant-related outcomes; and quality improvement initiatives. HSCT-TMA is a severe and potentially life-threatening complication that is often underdiagnosed. The collaboration of a multidisciplinary team of advanced practice providers, pharmacists, and physicians can optimize recognition, diagnosis, management, and monitoring of patients with HSCT-TMA, thereby improving outcomes for these patients.

Drug-induced thrombotic microangiopathy: An updated review of causative drugs, pathophysiology, and management

Drug-induced thrombotic microangiopathy (DITMA) represents 10%-13% of all thrombotic microangiopathy (TMA) cases and about 20%-30% of secondary TMAs, just behind pregnancy-related and infection-related forms. Although the list of drugs potentially involved as causative for TMA are rapidly increasing, the scientific literature on DITMA is quite scarce (mostly as individual case reports or little case series), leading to poor knowledge of pathophysiological mechanisms and clinical management. In this review, we focused on these critical aspects regarding DITMA. We provided an updated list of TMA-associated drugs that we selected from a scientific literature review, including only those drugs with a definite or probable causal association with TMA. The list of drugs is heterogeneous and could help physicians from several different areas to be familiar with DITMA. We describe the clinical features of DITMA, presenting the full spectrum of clinical manifestations, from systemic to kidney-limited forms. We also analyze the association between signs/symptoms (i.e., malignant hypertension, thrombocytopenia) and specific DITMA causative drugs (i.e., interferon, ticlopidine). We highlighted their multiple different pathophysiological mechanisms, being frequently classified as immune-mediated (idiosyncratic) and dose-related/toxic. In particular, to clarify the role of the complement system and genetic deregulation of the related genes, we conducted a revision of the scientific literature searching for DITMA cases who underwent renal biopsy and/or genetic analysis for complement genes. We identified a complement deposition in renal biopsies in half of the patients (37/66; 57%), with some drugs associated with major deposits (i.e., gemcitabine and ramucirumab), particularly in capillary vessels (24/27; 88%), and other with absent deposits (tyrosine kinase inhibitors and intraocular anti-VEGF). We also found out that, differently from other secondary TMAs (such as pregnancy-related-TMA and malignant hypertension TMA), complement genetic pathological mutations are rarely involved in DITMA (2/122, 1.6%). These data suggest a variable non-genetic complement hyperactivation in DITMA, which probably depends on the causative drug involved. Finally, based on recent literature data, we proposed a treatment approach for DITMA, highlighting the importance of drug withdrawal and the role of therapeutic plasma-exchange (TPE), rituximab, and anti-complementary therapy.

Exploratory Prognostic Biomarkers of Complement-Mediated Thrombotic Microangiopathy (CM-TMA) in Adults with Atypical Hemolytic Uremic Syndrome (aHUS): Analysis of a Phase III Study of Ravulizumab

BACKGROUND

Clinically validated biomarkers for monitoring of patients with complement-mediated thrombotic microangiopathy (CM-TMA) including atypical hemolytic uremic syndrome (aHUS) are unavailable. Improved characterization of biomarkers in patients with aHUS may inform treatment and monitoring for patients with CM-TMA.

METHODS

This analysis used data collected from 55/56 (98.2 %) adult patients with aHUS enrolled in the global Phase III study of ravulizumab (NCT02949128). Baseline (pre-treatment) patient serum, plasma and urine biomarker levels were compared with the maximum observed levels in normal donors and evaluated for associations with pre-treatment plasma exchange/infusion and dialysis status. Biomarkers were also assessed for associations with key clinical measures at baseline and with changes at 26 and 52 weeks from treatment initiation via linear regression analyses.

RESULTS

Complement-specific urine levels (factor Ba and sC5b-9) were elevated in >85 % of patients and are significantly associated with pre-treatment kidney dysfunction. Baseline levels of other evaluated biomarkers were elevated in >70 % of patients with aHUS, except for plasma sC5b-9 and serum sVCAM-1. Lower levels of urine complement markers at baseline are significantly associated with improvements in total urine protein and estimated glomerular filtration rate at 26 and 52 weeks of treatment. Clinical assessment of complement activation by a receiver operating characteristic analysis of Ba and sC5b-9 was more sensitive and specific in urine matrix than plasma.

CONCLUSION

This analysis identified a set of biomarkers that may show utility in the prognosis of CM-TMA, including their potential for measuring and predicting response to anti-C5 therapy. Further studies are required to enhance patient risk stratification and improve management of these vulnerable patients.

CLINICAL TRIALS REGISTRATION

NCT02949128, ClinicalTrials.gov.

Complement Mediated Endothelial Damage in Thrombotic Microangiopathies

Thrombotic microangiopathies (TMA) constitute a group of different disorders that have a common underlying mechanism: the endothelial damage. These disorders may exhibit different mechanisms of endothelial injury depending on the pathological trigger. However, over the last decades, the potential role of the complement system (CS) has gained prominence in their pathogenesis. This is partly due to the great efficacy of complement-inhibitors in atypical hemolytic syndrome (aHUS), a TMA form where the primary defect is an alternative complement pathway dysregulation over endothelial cells (genetic and/or adquired). Complement involvement has also been demonstrated in other forms of TMA, such as thrombotic thrombocytopenic purpura (TTP) and in Shiga toxin-producing Escherichia coli hemolytic uremic syndrome (STEC-HUS), as well as in secondary TMAs, in which complement activation occurs in the context of other diseases. However, at present, there is scarce evidence about the efficacy of complement-targeted therapies in these entities. The relationship between complement dysregulation and endothelial damage as the main causes of TMA will be reviewed here. Moreover, the different clinical trials evaluating the use of complement-inhibitors for the treatment of patients suffering from different TMA-associated disorders are summarized, as a clear example of the entry into a new era of personalized medicine in its management.

Is the Endothelium the Missing Link in the Pathophysiology and Treatment of COVID-19 Complications?

Patients with COVID-19 present a wide spectrum of disease severity, from asymptomatic cases in the majority to serious disease leading to critical care and even death. Clinically, four different scenarios occur within the typical disease timeline: first, an incubation and asymptomatic period; second, a stage with mild symptoms due mainly to the virus itself; third, in up to 20% of the patients, a stage with severe symptoms where a hyperinflammatory response with a cytokine storm driven by host immunity induces acute respiratory distress syndrome; and finally, a post-acute sequelae (PASC) phase, which present symptoms that can range from mild or annoying to actually quite incapacitating. Although the most common manifestation is acute respiratory failure of the lungs, other organs are also frequently involved. The clinical manifestations of the COVID-19 infection support a key role for endothelial dysfunction in the pathobiology of this condition. The virus enters into the organism via its interaction with angiotensin-converting enzyme 2-receptor that is present prominently in the alveoli, but also in endothelial cells, which can be directly infected by the virus. Cytokine release syndrome can also drive endothelial damage independently. Consequently, a distinctive feature of SARS-CoV-2 infection is vascular harm, with severe endothelial injury, widespread thrombosis, microangiopathy, and neo-angiogenesis in response to endothelial damage. Therefore, endothelial dysfunction seems to be the pathophysiological substrate for severe COVID-19 complications. Biomarkers of endothelial injury could constitute strong indicators of disease progression and severity. In addition, the endothelium could represent a very attractive target to both prevent and treat these complications. To establish an adequate therapy, the underlying pathophysiology and corresponding clinical stage should be clearly identified. In this review, the clinical features of COVID-19, the central role of the endothelium in COVID-19 and in other pathologies, and the potential of specific therapies aimed at protecting the endothelium in COVID-19 patients are addressed.

First Report in the Literature of Biopsy-Proven Noncollapsing Focal Segmental Glomerulosclerosis Relapse in a Second Renal Transplant Presenting With Thrombotic Microangiopathy: A Case Report

Primary focal segmental glomerulosclerosis (FSGS) is a podocytopathy with an irregular response to immunosuppressive therapies. FSGS relapse occurs in 30% to 80% of kidney grafts, and poor survival outcomes include large proteinuria and the nephrotic syndrome's cardinal clinical features. Thrombotic microangiopathy (TMA) is caused by endothelial injury due to complement dysregulation including acute kidney injury, proteinuria, and severe hypertension common renal presentations. Both pathologies have well-described genetic forms, but their relationship remains uncertain. FSGS lesions can be found in kidney biopsy specimens in patients with TMA, and TMA has been reported in patients with collapsing glomerulopathy. However, this combination has not been clearly described in renal transplant recipients. We present the case of a 22-year-old man who received his second kidney allograft and developed an early graft disfunction with nephrotic syndrome and clinical TMA. His background was remarkable for primary, biopsy-confirmed FSGS in childhood, and he started hemodialysis in 2006 and received a living donor kidney graft the same year. He presented with a FSGS relapse with malignant hypertension and seizures in the first posttransplant month and had an irregular response to plasma exchange and rituximab, and dialysis was reinitiated 10 years later. A total of 3 biopsies were performed after his second kidney transplant showing the evolution of a FSGS relapse with histologic and clinical TMA in the absence of identified genetic mutations. Partial responses to treatments with plasma exchange, eculizumab, and rituximab were obtained, but the allograft was lost after 26 months. This case is the first report of concomitant FSGS and TMA in a renal transplant recipient.

2021 update of the 2012 ICSH Recommendations for identification, diagnostic value, and quantitation of schistocytes: Impact and revisions

In 2012, the International Council for Standardization in Hematology (ICSH) published recommendations for the identification, quantitation, and diagnostic value of schistocytes. In the present review, the impact of these recommendations is evaluated. This work is based on citations in peer-reviewed papers published since 2012. The first 2012 ICSH Recommendations have also been revised to incorporate newly published data in the literature and current best laboratory practice. Recommended reference ranges have been proposed for healthy adults and full-term neonates of 1% or less schistocytes. More than 1% of morphologically identified schistocytes on the blood film are considered suspicious for thrombotic microangiopathy. For preterm infants, a normal level of 5% or less is recommended. The fragment red cell count (FRC) generated by some automated hematological analyzers provides a valuable screening tool for the presence of schistocytes. Specifically, the absence of FRCs can be used as a valuable parameter to exclude the presence of schistocytes on the blood film. The validity and usefulness of microscope schistocytes and automated FRCs, respectively, are discussed in the context of the laboratory diagnostic tests used for thrombotic microangiopathies.