Constipation and hemolytic uremic syndrome

BACKGROUND

Shiga toxin-producing Escherichia coli (STEC) hemolytic uremic syndrome (HUS) classically presents with diarrhea. Absence of diarrheal prodrome increases suspicion for atypical HUS (aHUS). Inability to obtain a fecal specimen for culture or culture-independent testing limits the ability to differentiate STEC-HUS and aHUS.

CASE-DIAGNOSIS/TREATMENT

Our patient presented with abdominal pain and constipation, and evaluation of pallor led to a diagnosis of HUS. There was a complete absence of diarrhea during the disease course. Lack of fecal specimen for several days delayed testing for STEC. Treatment for atypical HUS was initiated with complement-blockade therapy. PCR-testing for Shiga toxin from fecal specimen later returned positive. Alternative complement-pathway testing did not identify a causative genetic variant or anti-Factor H antibody. A diagnosis of STEC-HUS was assigned, and complement-blockade therapy was stopped.

CONCLUSION

Diagnosis of aHUS remains a diagnosis of exclusion, whereby other causes of HUS are eliminated with reasonable certainty. Exclusion of STEC is necessary and relies on testing availability and recognition of testing limitations. Diarrhea-negative STEC-HUS remains a minority of cases, and future research is needed to explore the clinical characteristics of these patients.

Hyperhydration to Improve Kidney Outcomes in Children with Shiga Toxin-Producing E. coli Infection: a multinational embedded cluster crossover randomized trial (the HIKO STEC trial)

BACKGROUND

Shiga toxin-producing E. coli (STEC) infections affect children and adults worldwide, and treatment remain solely supportive. Up to 15-20% of children infected by high-risk STEC (i.e., E. coli that produce Shiga toxin 2) develop hemolytic anemia, thrombocytopenia, and kidney failure (i.e., hemolytic uremic syndrome (HUS)), over half of whom require acute dialysis and 3% die. Although no therapy is widely accepted as being able to prevent the development of HUS and its complications, several observational studies suggest that intravascular volume expansion (hyperhydration) may prevent end organ damage. A randomized trial is needed to confirm or refute this hypothesis.

METHODS

We will conduct a pragmatic, embedded, cluster-randomized, crossover trial in 26 pediatric institutions to determine if hyperhydration, compared to conservative fluid management, improves outcomes in 1040 children with high-risk STEC infections. The primary outcome is major adverse kidney events within 30 days (MAKE30), a composite measure that includes death, initiation of new renal replacement therapy, or persistent kidney dysfunction. Secondary outcomes include life-threatening, extrarenal complications, and development of HUS. Pathway eligible children will be treated per institutional allocation to each pathway. In the hyperhydration pathway, all eligible children are hospitalized and administered 200% maintenance balanced crystalloid fluids up to targets of 10% weight gain and 20% reduction in hematocrit. Sites in the conservative fluid management pathway manage children as in- or outpatients, based on clinician preference, with the pathway focused on close laboratory monitoring, and maintenance of euvolemia. Based on historical data, we estimate that 10% of children in our conservative fluid management pathway will experience the primary outcome. With 26 clusters enrolling a mean of 40 patients each with an intraclass correlation coefficient of 0.11, we will have 90% power to detect a 5% absolute risk reduction.

DISCUSSION

HUS is a devastating illness with no treatment options. This pragmatic study will determine if hyperhydration can reduce morbidity associated with HUS in children with high-risk STEC infection.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05219110 . Registered on February 1, 2022.

The utility of platelet activation biomarkers in thrombotic microangiopathies

Primary thrombotic microangiopathies (TMAs) are observed in thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), while secondary TMAs have a wide range of etiologies. Early diagnosis and treatment of TMA are critical for patient well-being; however, distinguishing TTP from HUS on presentation is particularly challenging. Thrombocytopenia and platelet activation are central to different types of TMAs, thus limiting the utility of standard diagnostic approaches to evaluate the platelet function and hemostatic capacity. Alternative means of quantifying and monitoring changes to platelet activation and function are urgently needed. Activated platelets have been shown to interact with proteins of the complement and coagulation cascades and form part of inflammation processes engaged in TMA. Increased levels of platelet surface receptors as well as increased plasma levels of platelet-derived soluble proteins have been reported in TMAs. Elevated levels of platelet-leukocyte aggregates and platelet microparticles are also reported in different types of TMAs. Larger prospective evaluations of platelet activation markers in TMA using standardized assays, with comparison to cohorts of patients with thrombosis, coagulopathy, and thrombocytopenia, to evaluate the clinical usefulness of platelet markers in TMA are now needed. This review will summarize the current knowledge around platelet activation markers and critically evaluate their utility in diagnosis and prognosis of TMA patients.

Differential expression of the virulence gene nleB among Shiga toxin-producing Escherichia coli strains

Shiga toxin-producing Escherichia coli (STEC) is a zoonotic foodborne pathogen associated with hemolytic uremic syndrome (HUS) that vary in their ability to cause disease in humans. STEC represents a serious problem for public health and Argentina is the country with the highest HUS incidence worldwide. Non-LEE effector (nle) genes, present on pathogenicity islands (PAIs), encode translocated substrates of the type III secretion system (T3SS), which could have an important role in STEC virulence. Particularly, nleB is one of the main effector genes proposed as a virulence marker that is involved in the action of T3SS during the STEC infection. NleB inhibits the inflammatory response of the host cell allowing the bacteria to persist in the first stage of the infection. In order to identify the potential risk of STEC strains for public health, the aim of this study was to evaluate and compare basal nleB transcription of 24 STEC strains belonging to 10 serotypes isolated from cattle, food and patients. The results showed differences in nleB transcription among strains. Some non-O157:H7 strains presented transcription levels above the control, an O157:H7 HUS-producing strain. On the other hand, no significant differences were found in basal transcription levels associated with origin or serotype but differences were found between HUS and non-HUS strains. These differences in nleB transcription may be of importance in STEC pathogenesis and could help to differentiate high and low virulence STEC strains.

Syndromes of Thrombotic Microangiopathy

Thrombotic thrombocytopenia purpura (TTP) and the hemolytic uremic syndrome (HUS) are rare thrombotic microangiopathies that can be rapidly fatal. Although the acquired versions of TTP and HUS are generally highest on this broad differential, multiple rarer entities can produce a clinical picture similar to TTP/HUS, including microangiopathic hemolysis, renal failure, and neurologic compromise. More recent analysis has discovered a host of genetic factors that can produce microangiopathic hemolytic syndromes. This article discusses the current understanding of thrombotic microangiopathy and outlines the pathophysiology and causative agents associated with each distinct syndrome as well as the most accepted treatments.

Pathology Consultation on the Diagnosis and Treatment of Thrombotic Microangiopathies (TMAs)

OBJECTIVES

Pathologists specializing in transfusion medicine, apheresis medicine, and/or coagulation are often consulted by clinicians to reach a diagnosis for patients with thrombotic microangiopathy (TMA), so that disease-specific, often life-saving therapy can be initiated as promptly as possible.

METHODS

This article describes how to proceed when treating a patient with TMA. The differential diagnosis is broad and potentially very challenging. Thrombotic thrombocytopenic purpura (TTP), atypical hemolytic uremic syndrome (aHUS), and typical hemolytic uremic syndrome (HUS) are three such TMAs that require timely diagnosis and treatment.

RESULTS

TTP is treated with daily therapeutic plasma exchange (TPE) and commonly with adjunctive immunosuppressive therapy, while aHUS may initially be managed with TPE but is best controlled with eculizumab once a presumptive diagnosis is made. TPE has no proven role in typical HUS, which is most commonly treated with supportive measures only.

CONCLUSIONS

Prompt and accurate diagnosis of TMA subtypes optimizes treatment and improves patient outcomes.

Effect of antibiotics on cellular stress generated in Shiga toxin-producing Escherichia coli O157:H7 and non-O157 biofilms

Shiga toxin-producing Escherichia coli (STEC) are important food-borne pathogens, with the main virulence factor of this bacterium being its capacity to secrete Shiga toxins (Stxs). Therefore, the use of certain antibiotics for the treatment of this infection, which induces the liberation of Stxs, is controversial. Reactive oxygen and nitrogen species are also involved in the pathogenesis of different diseases. The purpose of this study was to analyze the effects of antibiotics on biofilms of STEC and the relationships between cellular stress and the release of Stx. To this end, biofilms of reference and clinical strains were treated with antibiotics (ciprofloxacin, fosfomycin and rifaximin) and the production of oxidants, the antioxidant defense system and toxin release were evaluated. Ciprofloxacin altered the prooxidant-antioxidant balance, with a decrease of oxidant metabolites and an increase of superoxide dismutase and catalase activity, being associated with high-levels of Stx production. Furthermore, inhibition of oxidative stress by exogenous antioxidants was correlated with a reduction in the liberation of Stx, indicating the participation of this phenomenon in the release of this toxin. In contrast, fosfomycin and rifaximin produced less alteration with a minimal production of Stx. Our data show that treatment of biofilm-STEC with these antibiotics induces oxidative stress-mediated release of Stx.

Age-Related Changes in Soluble Vascular Endothelial Growth Factor Receptor 1 (sVEGFR1) and Receptor 2 (sVEGFR2) in Healthy Japanese Subjects

We measured serum soluble vascular endothelial growth factor receptor 1 (sVEGFR1) and receptor 2 (sVEGFR2) levels in healthy Japanese individuals in order to establish a reference value using a specific ELISA. Significant differences were observed in serum sVEGFR1 and sVEGFR2 levels between children and adults. To demonstrate the usefulness of the reference value for children, we measured serum sVEGFR1 and sVEGFR2 levels in children with diarrhea positive (D+) hemolytic uremic syndrome (HUS) as a preliminary study. Serum sVEGFR2 levels in children with HUS were markedly higher than those in healthy children from the onset of D + HUS. The reference value for healthy children in the present study will allow normal and pathological conditions to be discriminated from each other in future study.

HUS and TTP in Children

This review describes the epidemiology, pathophysiology, presentation, clinical causes, treatment, and long-term prognosis of pediatric patients who present with thrombotic microangiopathy. The focus is on hemolytic uremic syndrome and thrombotic thrombocytopenic purpura, the most common phenotypes of thrombotic microangiopathy.

Adult-onset eculizumab-resistant hemolytic uremic syndrome associated with cobalamin C deficiency

A 20-year-old man was hospitalized for malignant hypertension, mechanical hemolysis, and kidney failure. Kidney biopsy confirmed glomerular and arteriolar thrombotic microangiopathy. Etiologic analyses, which included ADAMTS13 activity, stool culture, complement factor proteins (C3, C4, factor H, factor I, and MCP [membrane cofactor protein]), anti-factor H antibodies, HIV (human immunodeficiency virus) serology, and antinuclear and antiphospholipid antibodies, returned normal results. Malignant hypertension was diagnosed. Ten months later, we observed a relapse of acute kidney injury and mechanical hemolysis. Considering a diagnosis of complement dysregulation-related atypical hemolytic uremic syndrome (HUS), we began treatment with eculizumab. Despite the efficient complement blockade, the patient's kidney function continued to decline. We performed additional analyses and found that the patient's homocysteine levels were dramatically increased, with no vitamin B12 (cobalamin) or folate deficiencies. We observed very low plasma methionine levels associated with methylmalonic aciduria, which suggested cobalamin C disease. We stopped the eculizumab infusions and initiated specific treatment, which resulted in complete cessation of hemolysis. MMACHC (methylmalonic aciduria and homocystinuria type C protein) sequencing revealed compound heterozygosity for 2 causative mutations. To our knowledge, this is the first report of adult-onset cobalamin C-related HUS. Considering the wide availability and low cost of the homocysteine assay, we suggest that it be included in the diagnostic algorithm for adult patients who present with HUS.

Age-Related Changes of Serum Soluble Interleukin 9 Receptor (sIL-9Rα) in Healthy Subjects

Most cytokine receptors including interleukin (IL)-9 have soluble counterparts in body fluids. We planned to investigate the pathophysiological significance of the serum soluble IL-9 receptor (sIL-9R) level. We determined the serum sIL-9Rα chain (sIL-9Rα) levels in 96 healthy Japanese individuals to establish a control value by means of specific human sIL-9Rα ELISA, followed by a preliminary application in a patient with diarrhea positive hemolytic uremic syndrome. Age was negatively correlated with the sIL-9Rα level (Spearman r = -0.241, n = 96, p = 0.0180). The serum sIL-9Rα level showed a progressive decline to the normal adult level by the age of 30. The serum sIL-9Rα level of the patient with HUS was markedly higher than those of the age-matched control from the onset of the disease. Because of the remarkable age-dependent variability of sIL-9Rα in healthy subjects, disease-related changes, as well as therapy-dependent alterations, should be considered with caution. Thus, it is recommended that when the serum sIL-9Rα levels of patients are evaluated, the values should be compared with those of age-matched controls. The established control value will be used to discriminate between normal and the pathological conditions in our future studies.