Streptococcus Pneumoniae-Associated Hemolytic Uremic Syndrome in the Era of Pneumococcal Vaccine

Pneumococcal Hemolytic Uremic Syndrome in Children in Sweden

This cohort study of children in Sweden reviewed pneumococcal hemolytic uremic syndrome cases between 2009 and 2024 for incidence rates and serotype data.

Ten tips for managing complement-mediated thrombotic microangiopathies (formerly atypical hemolytic uremic syndrome): narrative review

Complement-mediated thrombotic microangiopathies (CM-TMA) are rare and life-threatening disorders characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ damage. These conditions result from dysregulation of the alternative complement pathway, often due to genetic variants or autoantibodies. The clinical spectrum is broad, comprising varied presentations and triggers, including infections, malignancies, and pregnancy-related complications. Advances in understanding the genetic and immunological basis of CM-TMA have improved diagnosis and treatment. Diagnosis requires exclusion of other thrombotic microangiopathies like thrombotic thrombocytopenic purpura and secondary causes, with genetic testing recommended to identify underlying susceptibilities. The introduction of C5 inhibitors has transformed the management of CM-TMA, significantly improving outcomes compared to the pre-2011 era when therapeutic plasma exchange was the primary therapy. Despite these advances, challenges remain in determining the optimal duration of therapy. Prophylactic measures against infections, particularly meningococcal disease, are mandatory for patients receiving C5 inhibitors. This article underscores the need for a personalized, multidisciplinary approach in the diagnosis and management of CM-TMA. Advances in genetics and complement biology have led to improved therapeutic strategies, however ongoing research is essential to address unanswered questions regarding relapse risk, treatment duration, and long-term outcomes.

Use of complement C5-inhibitor eculizumab in patients with infection-associated hemolytic uremic syndrome - a case-series report

BACKGROUND

Hemolytic uremic syndrome (HUS), characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury (AKI), remains a leading cause of pediatric AKI. The complement system has a crucial role in the pathogenesis of atypical hemolytic uremic syndrome (aHUS) and eculizumab (ECZ) was approved as standard of care for its treatment. The two widely characterized forms of infection-associated HUS are Shiga toxin-producing E. coli (STEC)-HUS and Streptococcus pneumoniae-associated (SP)-HUS. Extrarenal manifestations such as central nervous system (CNS) involvement occur approximately in 20% of the cases and are accompanied by higher mortality. Abnormalities of the alternative complement pathway may also contribute to the development of both STEC-HUS and SP-HUS, offering a potential treatment option for complement C5 inhibition. Beyond best supportive care as standard therapeutic approach, ECZ has been successfully used in both STEC-HUS and SP-HUS patients. We provide further support that early use of ECZ for infection-associated HUS with severe clinical manifestation and abnormal complement-activation profile may be an effective therapeutic approach.

CASE PRESENTATION

We report on three children (median age: 2 years, range: 2-10 years) diagnosed with infection-associated HUS treated with complement C5-inhibitor ECZ. All three patients were treated with ECZ and had excellent outcome. We retrospectively analyzed the clinical course, laboratory data and outcome of children with infection-associated HUS treated with ECZ.

CONCLUSION

In accordance with previous observations ECZ is an efficacious therapeutic choice in severe HUS patients with multiorgan involvement. A detailed complement activation profile, especially sC5b-9, is useful to indicate ECZ administration.

Bronchopleural fistula management in a pediatric patient requiring extracorporeal membrane oxygenation

Bronchopleural fistula (BPF) is a connection between the bronchus and pleural cavity. It is associated with high morbidity and mortality and management of BPF has not been well described in the pediatric population. We describe a 2-year-old girl who presented with fever and increased work of breathing, found to have atypical hemolytic uremic syndrome and Streptococcus necrotizing pneumonia with development of persistent air leak due to bronchopleural fistulas requiring extracorporeal membrane oxygenation (ECMO). Three endobronchial valves were placed with successful resolution of bronchopleural fistulas. She required tracheostomy for chronic respiratory failure and endobronchial valves were eventually removed. Approximately 3.5 months after discharge to acute care rehabilitation, tracheostomy was successfully decannulated. This case highlights the successful use of endobronchial valves for resolution of BPF while on ECMO as well as the importance of further studies on optimal candidates, timing and duration of intervention in addition to sequelae of endobronchial valve placement.

The role of pneumococcal extracellular vesicles on the pathophysiology of the kidney disease hemolytic uremic syndrome

Streptococcus pneumoniae-induced hemolytic uremic syndrome (Sp-HUS) is a kidney disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. This disease is frequently underdiagnosed and its pathophysiology is poorly understood. In this work, we compared clinical strains, isolated from infant Sp-HUS patients, with a reference pathogenic strain D39, for host cytotoxicity and further explored the role of Sp-derived extracellular vesicles (EVs) in the pathogenesis of an HUS infection. In comparison with the wild-type strain, pneumococcal HUS strains caused significant lysis of human erythrocytes and increased the release of hydrogen peroxide. Isolated Sp-HUS EVs were characterized by performing dynamic light-scattering microscopy and proteomic analysis. Sp-HUS strain released EVs at a constant concentration during growth, yet the size of the EVs varied and several subpopulations emerged at later time points. The cargo of the Sp-HUS EVs included several virulence factors at high abundance, i.e., the ribosomal subunit assembly factor BipA, the pneumococcal surface protein A, the lytic enzyme LytC, several sugar utilization, and fatty acid synthesis proteins. Sp-HUS EVs strongly downregulated the expression of the endothelial surface marker platelet endothelial cell adhesion molecule-1 and were internalized by human endothelial cells. Sp-HUS EVs elicited the release of pro-inflammatory cytokines (interleukin [IL]-1β, IL-6) and chemokines (CCL2, CCL3, CXCL1) by human monocytes. These findings shed new light on the overall function of Sp-EVs, in the scope of infection-mediated HUS, and suggest new avenues of research for exploring the usefulness of Sp-EVs as therapeutic and diagnostic targets. IMPORTANCE Streptococcus pneumoniae-associated hemolytic uremic syndrome (Sp-HUS) is a serious and underdiagnosed deadly complication of invasive pneumococcal disease. Despite the introduction of the pneumococcal vaccine, cases of Sp-HUS continue to emerge, especially in children under the age of 2. While a lot has been studied regarding pneumococcal proteins and their role on Sp-HUS pathophysiology, little is known about the role of extracellular vesicles (EVs). In our work, we isolate and initially characterize EVs from a reference pathogenic strain (D39) and a strain isolated from a 2-year-old patient suffering from Sp-HUS. We demonstrate that despite lacking cytotoxicity toward human cells, Sp-HUS EVs are highly internalized by endothelial cells and can trigger cytokine and chemokine production in monocytes. In addition, this work specifically highlights the distinct morphological characteristics of Sp-HUS EVs and their unique cargo. Overall, this work sheds new light into potentially relevant players contained in EVs that might elucidate about pneumococcal EVs biogenesis or pose as interesting candidates for vaccine design.

HUS and TTP: traversing the disease and the age spectrum

Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenia purpura (TTP) are rare diseases sharing a common pathological feature, thrombotic microangiopathy (TMA). TMA is characterized by microvascular thrombosis with consequent thrombocytopenia, microangiopathic hemolytic anemia and/or multiorgan dysfunction. In the past, the distinction between HUS and TTP was predominantly based on clinical grounds. However, clinical presentation of the two syndromes often overlaps and, the differential diagnosis is broad. Identification of underlying pathogenic mechanisms has enabled the classification of these syndromes on a molecular basis: typical HUS caused by Shiga toxin-producing Escherichia coli (STEC-HUS); atypical HUS or complement-mediated TMA (aHUS/CM-TMA) associated with genetic or acquired defects leading to dysregulation of the alternative pathway (AP) of complement; and TTP that results from a severe deficiency of the von Willebrand Factor (VWF)-cleaving protease, ADAMTS13. The etiology of TMA differs between pediatric and adult patients. Childhood TMA is chiefly caused by STEC-HUS, followed by CM-TMA and pneumococcal HUS (Sp-HUS). Rare conditions such as congenital TTP (cTTP), vitamin B12 metabolism defects, and coagulation disorders (diacylglycerol epsilon mutation) present as TMA chiefly in children under 2 years of age. In contrast secondary causes and acquired ADAMT13 deficiency are more common in adults. In adults, compared to children, diagnostic delays are more frequent due to the wide range of differential diagnoses. In this review we focus on the three major forms of TMA, STEC-HUS, aHUS and TTP, outlining the clinical presentation, diagnosis and management of the affected patients, to help highlight the salient features and the differences between adult and pediatric patients which are relevant for management.

Minor Cross-Matching in the Diagnosis of Pneumococcal Hemolytic Uremic Syndrome in an 18-Month-Old Boy

In developing nations, limitations in diagnostic facilities act as a barrier for differentiation of hemolytic uremic syndrome (HUS) based on the etiology. A sick-looking 18-month-old boy presented to our hospital in Bhubaneswar, India, with clinical signs and symptoms of left lobar pneumonia, abnormal hematological and renal parameters, no growth in blood culture, a negative direct antiglobulin test (DAT) result, and low complement levels. A rapid deterioration in his clinical condition necessitated intensive care support, blood transfusion, and renal replacement therapy (peritoneal dialysis and hemodialysis). Because his health care team suspected atypical HUS, therapeutic plasma exchange (TPE) was initiated as soon as possible. In the absence of a lectin panel, minor cross-matching confirmed T-antigen exposure. With a diagnosis of HUS induced by Streptococcus pneumoniae (sp-HUS), TPE was stopped immediately, and washed blood components were administered. Despite the aforementioned measures, the boy died of HUS on day 20 after presentation. This case emphasized the role of minor cross-matching in the detecting of polyagglutination in resolving the diagnostic dilemma of sp-HUS.

Thrombotic microangiopathies in critically ill children: The MATUCIP registry in Spain

INTRODUCTION

Thrombotic microangiopathies (TMA) are rare diseases usually presenting with renal, haematological, neurologic and cardiovascular involvement and nonspecific but severe symptoms. A registry of TMA cases managed in Spanish paediatric intensive care units (the MATUCIP Registry) was established with the aim of gaining knowledge on their clinical characteristics, diagnosis and acute-phase treatment.

METHODS

We conducted a prospective multicentre observational study in 20 paediatric intensive care units (PICUs) in Spain from January 2017 to December 2021 in children aged more than 1 month with TMAs, who were followed up through the discharge from the PICU.

RESULTS

The sample included 97 patients (51.5% female) with a median age of 2.6 years (interquartile range [IQR], 1.6-5.7). The initial manifestations were gastrointestinal (74.2%), respiratory (14.4%), fever (5.2%), neurologic (3.1%) and other (3.1%). At admission, 75.3% of patients had microangiopathic haemolytic anaemia, 95.9% thrombocytopenia and 94.8% acute kidney injury. Of the total sample, 57.7% of patients received a diagnosis of Shiga toxin-associated haemolytic uraemic syndrome (HUS), 14.4% of Streptococcus pneumoniae-associated HUS, 15.6% of atypical HUS, 10.3% of secondary TMA and 2.1% of thrombotic thrombocytopenic purpura. Eighty-seven patients (89.7%) developed arterial hypertension, and 49.5% gastrointestinal, 22.7% respiratory, 25.8% neurologic and 12.4% cardiac manifestations. Also, 60.8% required renal replacement therapy and 2.1% plasma exchange. Twenty patients received eculizumab. The median PICU stay was 8.5 days (IQR, 5-16.5). Two children died.

CONCLUSIONS

The MATUCIP registry demonstrates the clinical variability of TMA cases requiring admission to the PICU. Knowledge of the presentation and outcomes of TMAs can facilitate early aetiological diagnosis. This registry can help improve our understanding of the clinical spectrum of these diseases, for which there is a dearth of published data.