Characterization of patients with aHUS and associated triggers or clinical conditions: A Global aHUS Registry analysis

INTRODUCTION

Atypical haemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy (TMA) associated with complement dysregulation; aHUS may be associated with other 'triggers' or 'clinical conditions'. This study aimed to characterize this patient population using data from the Global aHUS Registry, the largest collection of real-world data on patients with aHUS.

METHODS

Patients enrolled in the Global aHUS Registry between April 2012 and June 2021 and with recorded aHUS-associated triggers or clinical conditions prior/up to aHUS onset were analysed. aHUS was diagnosed by the treating physician. Data were classified by age at onset of aHUS (< or ≥18 years) and additionally by the presence/absence of identified pathogenic complement genetic variant(s) and/or anti-complement factor H (CFH) antibodies. Genetically/immunologically untested patients were excluded.

RESULTS

1947 patients were enrolled in the Global aHUS Registry by June 2021, and 349 (17.9%) met inclusion criteria. 307/349 patients (88.0%) had a single associated trigger or clinical condition and were included in the primary analysis. Malignancy was most common (58/307, 18.9%), followed by pregnancy and acute infections (both 53/307, 17.3%). Patients with an associated trigger or clinical condition were generally more likely to be adults at aHUS onset.

CONCLUSION

Our analysis suggests that aHUS-associated triggers or clinical conditions may be organized into clinically relevant categories, and their presence does not exclude the concurrent presence of pathogenic complement genetic variants and/or anti-CFH antibodies. Considering a diagnosis of aHUS with associated triggers or clinical conditions in patients presenting with TMA may allow faster and more appropriate treatment.

Outcome of atypical hemolytic uremic syndrome: role of triggers and complement abnormalities in the response to C5 inhibition

BACKGROUND

Atypical-hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy often due to uncontrolled complement activation, characterized by high risk of end-stage kidney disease (ESKD). Eculizumab has improved the outcome, however, its efficacy varies among patients and its discontinuation is debated.

METHODS

To identify characteristics associated with treatment response, we analyzed 244 aHUS patients referred to our center. Patients were classified according to the presence/absence of complement abnormalities and/or triggers at onset in 4 categories: (1) primary (complement abnormality without trigger), (2) secondary (trigger without complement abnormality), (3) combined (trigger and complement abnormality), (4) idiopathic (no trigger, no complement abnormality). Response to treatment was evaluated by comparing the response to eculizumab with that of conventional therapy. Short- and long-term outcomes were evaluated with the relapse rate after discontinuation of C5-inhibition.

RESULTS

Patients had a better outcome with eculizumab compared to conventional treatment, with a response rate of 81.9% vs 56.9%, p < 0.001 and a long-term cumulative incidence of ESKD of 5.8% vs 22.5% (hazard ratio 0.25, 95% confidence interval: 0.10-0.80). The excellent global response was driven by the primary and combined groups (89.8% vs 54.0% and 89.3% vs 54.2%, respectively). The relapse rate following discontinuation of the C5-inhibitor was as high as 66.7% in the primary group, 18.7% in the combined, and 0% in the secondary and idiopathic groups.

CONCLUSIONS

Our data show a better outcome in aHUS patients treated with C5-inhibition, particularly in the primary and combined forms, which have a high risk of relapse after discontinuation that is not observed in the secondary and idiopathic forms.

Detection of Cleaved Stx2a in the Blood of STEC-Infected Patients

Typical hemolytic uremic syndrome (HUS) is mainly caused by Shiga toxin-producing Escherichia coli (STEC) releasing Shiga toxin 2 (Stx2). Two different structures of this AB5 toxin have been described: uncleaved, with intact B and A chains, and cleaved, with intact B and a nicked A chain consisting of two fragments, A1 and A2, connected by a disulfide bond. Despite having the same toxic effect on sensitive cells, the two forms differ in their binding properties for circulating cells, serum components and complement factors, thus contributing to the pathogenesis of HUS differently. The outcome of STEC infections and the development of HUS could be influenced by the relative amounts of uncleaved or cleaved Stx2 circulating in patients' blood. Cleaved Stx2 was identified and quantified for the first time in four out of eight STEC-infected patients' sera by a method based on the inhibition of cell-free translation. Cleaved Stx2 was present in the sera of patients with toxins bound to neutrophils and in two out of three patients developing HUS, suggesting its involvement in HUS pathogenesis, although in association with other bacterial or host factors.

Enzymatic Cleavage of Stx2a in the Gut and Identification of Pancreatic Elastase and Trypsin as Possible Main Cleavers

Shiga toxins (Stxs), especially the Stx2a subtype, are the major virulence factors involved in enterohemorrhagic Escherichia coli (EHEC)-associated hemolytic uremic syndrome (eHUS), a life-threatening disease causing acute kidney injury, especially in children. After oral transmission and colonization in the gut, EHEC release Stx. Intracellular cleavage of the Stx A subunit, when followed by reduction, boosts the enzymatic activity that causes damage to targeted cells. This cleavage was assumed to be mostly mediated by furin during Stx intracellular trafficking. To investigate whether this cleavage could occur in the intestine, even prior to entering target cells, Stx2a A subunit structure (intact or cleaved) was characterized after its exposure to specific host factors present in human stool. The molecular weight of Stx2a A subunit/fragments was determined by immunoblotting after electrophoretic separation under reducing conditions. In this study, it was demonstrated that Stx2a is cleaved by certain human stool components. Trypsin and chymotrypsin-like elastase 3B (CELA3B), two serine proteases, were identified as potential candidates that can trigger the extracellular cleavage of Stx2a A subunit directly after its secretion by EHEC in the gut. Whether the observed cleavage indeed translates to natural infections and plays a role in eHUS pathogenesis has yet to be determined. If so, it seems likely that a host's protease profile could affect disease development by changing the toxin's biological features.

Clinical characteristics and outcomes of a patient population with atypical hemolytic uremic syndrome and malignant hypertension: analysis from the Global aHUS registry

INTRODUCTION

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy (TMA) often caused by alternative complement dysregulation. Patients with aHUS can present with malignant hypertension (MHT), which may also cause TMA.

METHODS

This analysis of the Global aHUS Registry (NCT01522183) assessed demographics and clinical characteristics in eculizumab-treated and not-treated patients with aHUS, with (n = 71) and without (n = 1026) malignant hypertension, to further elucidate the potential relationship between aHUS and malignant hypertension.

RESULTS

While demographics were similar, patients with aHUS + malignant hypertension had an increased need for renal replacement therapy, including kidney transplantation (47% vs 32%), and more pathogenic variants/anti-complement factor H antibodies (56% vs 37%) than those without malignant hypertension. Not-treated patients with malignant hypertension had the highest incidence of variants/antibodies (65%) and a greater need for kidney transplantation than treated patients with malignant hypertension (65% vs none). In a multivariate analysis, the risk of end-stage kidney disease or death was similar between not-treated patients irrespective of malignant hypertension and was significantly reduced in treated vs not-treated patients with aHUS + malignant hypertension (adjusted HR (95% CI), 0.11 [0.01-0.87], P = 0.036).

CONCLUSIONS

These results confirm the high severity and poor prognosis of untreated aHUS and suggest that eculizumab is effective in patients with aHUS ± malignant hypertension. Furthermore, these data highlight the importance of accurate, timely diagnosis and treatment in these populations and support consideration of aHUS in patients with malignant hypertension and TMA.

TRIAL REGISTRATION DETAILS

Atypical Hemolytic-Uremic Syndrome (aHUS) Registry. Registry number: NCT01522183 (first listed 31st January, 2012; start date 30th April, 2012).

MO194: A Rare Case of Secondary Haemolytic Uremic Syndrome after ANTI-SARS-COV-2 Vaccination

BACKGROUND AND AIMS

Haemolytic uremic syndrome (HUS) is a rare disease characterized by macroangiopathic haemolytic anaemia, thrombocytopaenia and severe AKI, belonging to the thrombotic microangiopathies (TMAs). It is divided into typical and atypical HUS: the first one occurs most frequently in children within the first 5 years of life and it is associated with Shiga-like toxin producing Escherichiacoli infection; the second one (aHUS) is less common (10%) and it is due to complement abnormalities with coexisting disease or trigger such as autoimmunity, transplantation, cancer, infection, certain cytotoxic drugs or pregnancy. There is an increasing interest in SARS-CoV-2 infection as new trigger for complement activation. Nine cases of aHUS were recently associated with COVID-19, most of them occurring within 1 month from the infection. Available data suggest that SARS-CoV-2 is a potential trigger for aHUS: it can induce an over inflammatory state and to activate coagulation and complement pathway. Likewise, mRNA-based vaccines against COVID-19 inducing the expression of SARS-CoV-2 spike protein to stimulate immune recognition and antibody response could be a suitable trigger for HUS.

METHOD

We report the case of a 17-year-old woman, who presented at our emergency department with fever, dyspnoea, acute kidney injury AKI III with anuria, hypertension, severe anaemia, no diarrhoea, severe thrombocytopaenia and myocarditis, about 2 weeks after the first administration of SARS-CoV-2 vaccine (Comirnaty) and recent exposition to SARS-CoV-2 positive individual. SARS-CoV-2 nasal PCR swab was negative (as well as successive ones) and she was immediately admitted to paediatric intensive care unit and treated with transfusions and haemodialysis. Laboratory exams suggested a thrombotic microangiopathy with normal ADAMTS-13 activity and no E. coli infection. She underwent a renal biopsy that confirmed our hypothesis of aHUS: wrinkled capillaries, subendothelial expansion, mesangiolysis and rare thrombi in capillaries lumen. Arterioles had intimal proliferation with mucoid oedema who gave rise to onionskin like lesion that obliterates lumens. One glomerulus showed extracapillary proliferation (crescent), and there was interstitial lymphomonocytic inflammatory infiltration in the nearby. Also signs of acute tubular injury and atrophy were reported. Positive stain to fibrinogen in the arterioles at immunohistology was noted. She immediately performed genetic exams for aHUS-related complement mutations and she started immunosuppression with corticosteroids and eculizumab infusions. After 2 months of eculizumab, she was still oliguric, requiring renal replacement therapy. Genetic analysis showed no mutations. Therefore, she was examined for other genetic causes of thrombotic microangiopathies.

RESULTS

Finally, came to light that she had high levels of homocysteine, and she was diagnosed with secondary HUS associated with cobalamin C deficiency, which manifests with methylmalonic aciduria and homocystinuria due to a recessive mutation in the MMACHC gene, causing a cobalamin C type deficiency, which is the common functional variant of vitamin B12. After metabolic therapy with hydroxocobalamin, she gradually recovered diuresis and partially renal function without need for replacement therapy.

CONCLUSION

Reports from immunization programs show as myocarditis and thrombotic thrombocytopaenia are considered among main serious complications caused by COVID-19 vaccines, representing 12.6 cases per million doses and 0.73 cases per 100 000, respectively.

This interesting case probably supports data about the role of mRNA-based anti-SARS-CoV-2 vaccines like a precipitant factor for TMAs. Moreover, our patient turned out to be an extremely rare case of HUS secondary to cobalamin C deficiency, that is generally diagnosed in early infancy and show typically neurological symptoms (absent in our case). Probably, the mRNA-based vaccine acted like ‘a second hit’, but existing predisposition should always be investigated including also the less frequent forms.

FC 115: Long-Term Outcomes in Eculizumab-Treated Kidney Transplant Patients Enrolled in the Global Atypical Haemolytic Uraemic Syndrome Registry

BACKGROUND AND AIMS

The global atypical haemolytic uraemic syndrome (aHUS) registry (NCT01522183), the largest repository of real-world data on patients with aHUS, provides key insights into disease course, natural history, and patient (pt) outcomes with and without complement inhibitor therapy. Prior to eculizumab availability, pts with aHUS had a reportedly high risk of disease recurrence and graft loss following a kidney transplant (KTx). We report the long-term clinical outcomes of eculizumab-treated pts who received a KTx.

METHOD

This analysis included pts enrolled from April 2012–November 2021. Pts were included in a long-term treatment outcomes study if they had ever been treated with eculizumab and were excluded if they had DGKE mutations or their diagnosis was later revised to any condition other than aHUS. The current analysis set included pts who had received a KTx no more than 30 days prior to eculizumab start or up to 60 days post eculizumab start date, had ≥3 years of follow-up (FU) post-transplant and had serum creatinine (SCr) measurements at baseline (BL) and post 3 years FU. Changes in kidney function, haematological parameters and clinical characteristics at last follow-up (LFU) were assessed.

RESULTS

A total of 329/1970 adult and paediatric registry pts met the inclusion criteria and received a KTx; 78 pts from 12 countries met sub-group inclusion criteria. BL demographics are shown in Table 1. Mean (SD) treatment duration was 5.7 (2.4) years and 47 (60%) pts had pathogenic genetic variants. Lab parameters at BL (closest measurement at or following KTx) and LFU are reported in Table 2. Despite large ranges, median SCr levels remained stable at LFU. Median eGFR and platelet levels were similar at BL and LFU, while lower median lactose dehydrogenase levels were seen at LFU. At LFU: four pts (5%)—three adult—had subsequent KTx(s); eight (10%)—seven adults—had received dialysis by last observation; and two (3%) had received plasma exchange/infusion. Two pts (3%) died during the observation period.

CONCLUSION

This study assessed a large, real-world population of pts at high risk of KTx failure. Lab parameters suggest most pts benefitted from eculizumab treatment, with few TMA-related complications and stable kidney function and haematological parameters for ≥3 years. Overall, the proportions of female pts and of pts with pathogenic genetic variants were consistent with previous studies. A potential study limitation was the relatively stringent sub-population-specific inclusion criteria. However, these data further demonstrate the beneficial impact of eculizumab treatment in the long-term management of aHUS in pts requiring KTx.

Eculizumab treatment in atypical hemolytic uremic syndrome: correlation between functional complement tests and drug levels

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is characterized by platelet consumption, hemolysis, and renal injury. Eculizumab, a humanized antibody that blocks complement activity, has been successfully used in aHUS, but the best treatment schedule has not yet been clearly defined.

METHODS

Herein we report our experience with eculizumab maintenance treatment, in which the interval between subsequent doses was adjusted based on classical complement pathway (CCP) activity, targeted to < 30% for the prevention of relapses. Trough circulating levels of free eculizumab were determined by an immunoenzymatic method. Genetic and serologic characteristics of the patients were also assessed.

RESULTS

We report on 38 patients with aHUS with a median age of 25.0 years (range 0.5-60.0 years) treated with eculizumab. Once stable disease remission was obtained, the interval between eculizumab doses was extended based on target CCP activity. With this approach, presently, 22 patients regularly receive eculizumab infusion every 28 days and 16 receive it every 21. During a median observation period of 32.3 months (range 4.0-92.4 months) and a cumulative period of 1295 months, no patient relapsed. An inverse correlation between CCP activity and eculizumab circulating levels was present (r = - 0.690, p = 0.0001), with CCP activity being inhibited as long as free eculizumab was measurable in serum.

CONCLUSIONS

In patients with aHUS on eculizumab maintenance treatment, complement activity measurement can be used as a proxy for circulating levels of the drug. Monitoring complement activity allows for safe tailoring of the frequency of eculizumab administration, thus avoiding excessive drug exposure while keeping the disease in remission.

Fluid intake and blood pressure in children: the Salus per Aquam project

BACKGROUND

Sodium intake is known to contribute to the development of hypertension, thus intake reduction is a cornerstone in the prevention and management of hypertension. The increase in renal sodium excretion might represent a further potential preventive and/or therapeutic opportunity.

OBJECTIVE

To explore the working hypothesis that an increased fluid intake can improve renal sodium handling towards a decrease in blood pressure.

METHODS

The SPA Project is a multicenter, observational, cross-sectional, cohort study investigating healthy children, aged 5-8 years as to sodium and fluid intake by means of urinary sodium and creatinine from multiple samples taken in different days in order to characterize them in lower/higher sodium and lower/higher fluid intake. Both SBP and DBP (by multiple office blood pressure measurements) were used as outcome measures.

RESULTS

Three hundred and thirty-nine healthy, nonoverweight children (51.6% boys) with a median age of 5.7 years old (IQR: 5.3-6.2) participated in the study but only 223 could be analyzed. Among children with higher sodium intake, those introducing more fluids, showed a significantly lower blood pressure (both systolic and diastolic) compared with those with lower fluid intake: systolic 86.0 ± 8.5 vs. 90.0 ± 8.1 mmHg; P = 0.014 and diastolic: 53.8 ± 4.9 vs. 58.6 ± 6.6 mmHg; P < 0.0001.

CONCLUSION

An increased fluid intake is associated with a reduced blood pressure possibly by increasing renal sodium excretion. We speculate that this simple, highly acceptable, inexpensive, and harmless measure might have a role in preventing and/or minimizing the epidemics of hypertension and of its related morbidities both in children and in adults.

Multiple, random spot urine sampling for estimating urinary sodium excretion

The measurement of sodium intake may be important for the management of hypertension. Dietary surveys and 24-h urinary collection are often unreliable and/or impractical. We hypothesized that urinary sodium excretion can be accurately estimated through multiple spot urine samples from different days. All enrolled subjects were children of the coauthors of the study. Fifty-two 24-h urinary collections (4 per subject) for measuring sodium excretion and the 297 related urinary samples (1 per voiding) were collected for calculating the urinary sodium/urinary creatinine ratio in 13 children. The mean of 4 measured sodium excretions served as the individual "gold standard". Twenty-four urinary collections were used to generate the equation predicting the mean measured sodium excretion from the mean of 4 urinary sodium/urinary creatinine [= 0.016 × urinary sodium (mmol/L) / urinary creatinine (mmol/L) ratio + 3.3)]; the remaining 28 urinary collections and 153 urinary samples were used for the external validation. All subjects underwent an additional validation procedure involving 12 urinary samples randomly collected on different days 6 months apart. The performance of sodium excretion calculated from a total of over 22,000 possible means of 4 out of all the available urinary samples, randomly taken on different days, was analyzed as to precision (by means of the coefficient of variation) and as to accuracy (by means of the P30). The coefficients of variations of measured vs. calculated sodium excretion were 25.3% vs. 25.8%, and the P30 of calculated sodium excretion was 100%. The excellent performance of calculated sodium excretion was confirmed both by external validation and by samples collected 6 months apart with mean P30s, all between 86 and 100%.Conclusion: In the described experimental conditions, urinary sodium excretion was estimated with equal precision and more accurately (and practically) by the mean of 4 urinary sodium/urinary creatinine ratios from random samples from different days than by a single urinary collection. In real life, with several errors systematically affecting urinary collection, the superiority of calculated sodium excretion is likely to be even greater. What is Known: • The measurement of sodium intake with the current standards of care (dietary survey or 24-h urinary collection) is laborious and can be inaccurate. What is New: • The study provides evidence that sodium intake can be estimated equally precisely, more accurately and more practically with the urinary sodium-to-urinary creatinine ratio from 4 urine samples taken on different days than with a single urinary collection.

Glucose Control in Post-hemolytic-Uremic Syndrome Diabetes: A New Approach Offered by Sensor-Augmented Pump Therapy

We report the case of a 3-year-old girl admitted to her town emergency department for fever (39°C) associated with diarrhea, generalized edema, oliguria, and drowsiness. The blood test revealed metabolic acidosis, leucocytosis, increased inflammatory markers, anemia, thrombocytopenia, and acute kidney failure. Based on the diagnosis of hemolytic-uremic syndrome, the patient was referred to a third-level children hospital. Assisted ventilation, hemodialysis, and parenteral nutrition were instituted. The blood glucose levels increased above 200 mg/dl with peaks at 500 mg/dl. Islet auto-antibodies were negative and C-peptide was undetectable, thus ruling out the diagnosis of type 1 diabetes. Multiple-daily-injection insulin therapy was then instituted with the following regimen: Detemir 2 U once daily and Aspart 0.5 U if blood glucose >200 mg/dl. Despite the very low insulin dosage, the patient experienced frequent and severe hypoglycemic events during the following 24 h and was therefore switched to sensor-augmented pump therapy. Optimal glucose control was achieved without further hypoglycemic episodes. Moreover, thanks to the possibility to customize insulin therapy hour by hour during the day and the use of a pre-low glucose suspend system, glucose control was maintained even despite the continuous modifications in the nutritional scheme due to the multiple complications that arose during hospitalization. This rare case of post-hemolytic-uremic syndrome diabetes, treated with sensor-augmented therapy from its outbreak, suggests for the first time the potential of this therapeutic strategy in achieving glucose control without significant hypoglycemic episodes in children with secondary forms of diabetes associated with very low insulin requirement.

Bloody Diarrhea and Shiga Toxin-Producing Escherichia coli Hemolytic Uremic Syndrome in Children: Data from the ItalKid-HUS Network

OBJECTIVE

To analyze the results of an enhanced laboratory-surveillance protocol for bloody diarrhea aimed at identifying children with Shiga toxin-producing Escherichia coli (STEC) infection early in the course of the disease toward the early identification and management of patients with hemolytic uremic syndrome (HUS).

STUDY DESIGN

The study (2010-2019) involved a referral population of 2.3 million children. Stool samples of patients with bloody diarrhea were screened for Shiga toxin (Stx) genes. Positive patients were rehydrated and monitored for hemoglobinuria until diarrhea resolved or STEC-HUS was diagnosed.

RESULTS

A total of 4767 children were screened; 214 (4.5%) were positive for either Stx1 (29.0%) or Stx2 (45.3%) or both Stx1+2 (25.7%); 34 patients (15.9%) developed STEC-HUS (0.71% of bloody diarrheas). Hemoglobinuria was present in all patients with HUS. Patients with Stx2 alone showed a greater risk of STEC-HUS (23.7% vs 12.7%) and none of the patients with Stx1 alone developed HUS. During the same period of time, 95 other patients were diagnosed STEC-HUS but were not captured by the screening program (26 had nonbloody diarrhea, 11 came from areas not covered by the screening program, and 58 had not been referred to the screening program, although they did meet the inclusion criteria). At HUS presentation, serum creatinine of patients identified by screening was significantly lower compared with that of the remaining patients (median 0.9 vs 1.51 mg/dL).

CONCLUSIONS

Nearly 1% of children with bloody diarrhea developed STEC-HUS, and its diagnosis was anticipated by the screening program for Stx. The screening of bloody diarrhea for Stx is recommended, and monitoring patients carrying Stx2 with urine dipstick for hemoglobinuria is suggested to identify the renal complication as early as possible.

Pregnancy in Women with Atypical Hemolytic Uremic Syndrome

BACKGROUND

Pregnancy outcomes in patients with atypical hemolytic uremic syndrome (aHUS) are not well-documented. Here, we present characteristics of and outcomes for patients with aHUS who became pregnant while enrolled in the Global aHUS Registry.

METHODS

The observational Global aHUS Registry (NCT01522183), initiated in April 2012, collects demographics, disease history, treatment, and outcomes data for patients with aHUS, regardless of treatment approach. This descriptive analysis includes patients from the Registry with evaluable pregnancy data supplemented with pharmacovigilance information; the number of pregnancies, outcomes, and exposure to eculizumab were evaluated.

RESULTS

As of April 1, 2019, 44 pregnancies were recorded in 41 patients, with 24 pregnancies exposed to eculizumab. Pathogenic variants were identified in 48.8% of patients. Three patients were on dialysis and 6 patients had a kidney graft at the time of pregnancy. Excluding elective terminations, 85.3% of pregnancies resulted in live births. Elective terminations were recorded in 22.7% of pregnancies, miscarriages occurred in 9.1% of pregnancies, and late fetal death in 2.3% of pregnancies. No malformations or anomalies were reported.

CONCLUSIONS

Our results show that in women with aHUS, even on dialysis or with a kidney graft, pregnancy is possible with careful monitoring for aHUS flares and prematurity. Prophylactic or therapeutic eculizumab offers disease control with low-risk of fetal abnormalities.

Fenoldopam and renal hemodynamics in shiga toxin-related hemolytic uremic syndrome

BACKGROUND

Fenoldopam, a vasodilating agent, may represent a potential therapeutic opportunity to increase renal perfusion in those conditions where renal hemodynamics are severely impaired by vascular sub-occlusion, as, indeed, is the case in thrombotic microangiopathies.

METHODS

The renal resistance index (RRI) was measured, on and off fenoldopam, in 27 children with STEC-HUS.

RESULTS

A 12% decrease in RRI was observed on fenoldopam compared to off treatment without changes in the systemic hemodynamics and with no side effects.

CONCLUSIONS

If confirmed in larger series, fenoldopam may become an important addition to supportive care to reduce ischemic damage in STEC-HUS and improve long-term outcomes.

Thrombotic Microangiopathy Associated with Macrophage Activation Syndrome: A Multinational Study of 23 Patients

OBJECTIVE

To describe the clinical characteristics, treatment, and outcomes of a multinational cohort of patients with macrophage activation syndrome (MAS) and thrombotic microangiopathy (TMA).

STUDY DESIGN

International pediatric rheumatologists were asked to collect retrospectively the data of patients with the co-occurrence of MAS and TMA. Clinical and laboratory features of patients with systemic juvenile idiopathic arthritis (sJIA)-associated MAS and TMA were compared with those of an historical cohort of patients with sJIA and MAS.

RESULTS

Twenty-three patients with MAS and TMA were enrolled: 17 had sJIA, 2 systemic lupus erythematosus, 1 juvenile dermatomyositis, 1 mixed connective tissue disease, and 2 undifferentiated connective tissue disease. Compared with the historical cohort of MAS, patients with sJIA with coexistent MAS and TMA had higher frequencies of renal failure and neurologic involvement, hemorrhage, jaundice, and respiratory symptoms, as well as more severe anemia and thrombocytopenia, higher levels of alanine aminotransferase, lactate dehydrogenase, bilirubin and D-dimer, and lower levels of albumin and fibrinogen. They also required admission to the intensive care unit more frequently. Among patients tested, complement abnormalities and reduced ADAMTS13 activity were observed in 64.3% and 44.4% of cases, respectively. All patients received glucocorticoids. Treatment for TMA included plasma-exchange, eculizumab, and rituximab.

CONCLUSIONS

The possible coexistence of MAS and TMA in rheumatic diseases may be underrecognized. This association should be considered in patients with MAS who develop disproportionate anemia, thrombocytopenia, and lactate dehydrogenase increase, or have multiorgan failure.

Calcium carbonate-enriched cheese to improve nutrition, compliance and phosphorus control in patients on kidney replacement therapy

Background

Patients on renal replacement therapy face many dietary limitations, and cheese is often limited because of its high phosphate content; we have developed cheese with added calcium carbonate (CaCO₃) to provide patients with a nutritional opportunity while improving their phosphate control.

Methods

The present double-blind crossover study was aimed to compare the new modified cheese with an equivalent standard product in 16 patients. The increase in inter-dialysis phosphorus (ΔP) and pre-dialysis calcium were used as the primary endpoints for efficacy and safety.

Results

The median ΔP (and IQR) was significantly lower with the modified cheese compared with the standard product: 2.5 (1.9–2.9) mg/dL vs. 2.7 (2.2–3.4) mg/dL, respectively (p < 0.02). No difference was observed in pre-dialysis serum calcium levels.

Conclusions

The described modified cheese may represent an interesting means of overcoming some of the dietary limitations in patients on dialysis to help them achieve better nutrition and quality of life.

Graphic abstract

MO107CLINICAL CHARACTERISTICS OF A PATIENT POPULATION WITH ATYPICAL HAEMOLYTIC URAEMIC SYNDROME AND MALIGNANT HYPERTENSION: THE GLOBAL AHUS REGISTRY ANALYSIS

Background and Aims

Atypical haemolytic uraemic syndrome (aHUS) is a rare disease that manifests as complement-mediated thrombotic microangiopathy (TMA), which can lead to severe organ damage. Some patients with aHUS may present with malignant hypertension (MHT); both conditions can result in TMA. The objective of this analysis was to characterise patients with aHUS and MHT.

Method

In this analysis, patients from the Global aHUS Registry (NCT01522183) were included if they were diagnosed with MHT and were followed ≥90 days after initial aHUS symptom presentation or diagnosis date; patients were excluded if they withdrew from the registry or discontinued treatment with eculizumab due to a diagnosis other than aHUS. Demographics and clinical characteristics were evaluated.

Results

Seventy-one of 1903 registry patients were included in the analysis. Clinical characteristics are presented in the table. Seventeen patients (24%) had a paediatric (&lt;18 years) onset of disease, and 54 (76%) were adults at aHUS diagnosis; female patients were slightly overrepresented (61%). Sixty-nine percent of patients were reported to have MHT at around the same time as aHUS diagnosis (+/-2 months), while 11% and 13% experienced MHT before and after aHUS diagnosis, respectively. aHUS triggering conditions were reported in 6/71 patients (8%) (Table). Cardiovascular (27%) and gastrointestinal (21%) symptoms were the most commonly reported extra-renal manifestations. Eight patients (11%) had a reported family history of aHUS and 40 patients (56%) had a complement pathogenic variant or an anti-CFH-antibody. Thirty-three patients (46%) had a kidney transplant; of these, 20 were prescribed eculizumab in the peri- or post-transplant period.

Conclusion

In this analysis of patients with aHUS and MHT, the observed high prevalence of pathogenic variants in complement genes or anti-CFH antibodies, alongside the high proportion of patients with extrarenal manifestations and/or requiring kidney transplant, indicate a high severity of presentation and poor prognosis of aHUS associated with MHT.

Kidney transplant in patients with atypical hemolytic uremic syndrome in the anti-C5 era: single-center experience with tailored Eculizumab

RATIONALE AND OBJECTIVE

Patients with atypical hemolytic uremic syndrome (aHUS) have long been considered ineligible for kidney transplantation (KTx) in several centers due to the high risk of disease recurrence, graft loss and life-threatening complications. The availability of Eculizumab (ECU) has now overcome this problem. However, the best approach towards timing, maintenance schedule, the possibility of discontinuation and patient monitoring has not yet been clearly established.

STUDY DESIGN

This is a single center case series presenting our experience with KTx in aHUS.

SETTING AND PARTICIPANTS

This study included 26 patients (16 females) with a diagnosis of aHUS, who spent a median of 5.5 years on kidney replacement therapy before undergoing KTx. We compared the aHUS relapse rate in three groups of patients who underwent KTx: patients who received no prophylaxis, patients who underwent plasma exchange, those who received Eculizumab prophylaxis. Complement factor H-related disease was by far the most frequent etiology (n = 19 patients).

RESULTS

Untreated patients and patients undergoing pre-KTx plasma exchange prophylaxis had a relapse rate of 0.81 (CI 0.30-1.76) and 3.1 (CI 0.64-9.16) events per 10 years cumulative observation, respectively, as opposed to 0 events among patients receiving Eculizumab prophylaxis. The time between Eculizumab doses was tailored based on classic complement pathway activity (target to < 30%). Using this strategy, 12 patients are currently receiving  Eculizumab every 28 days, 5 every 24-25 days, and 3 every 21 days.

CONCLUSION

Our experience supports the prophylactic use of Eculizumab in patients with a previous history of aHUS undergoing KTx, especially when complement dysregulation is well documented by molecular biology.

IgM Autoantibodies to Complement Factor H in Atypical Hemolytic Uremic Syndrome

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS), a severe thrombotic microangiopathy, is often related to complement dysregulation, but the pathomechanisms remain unknown in at least 30% of patients. Researchers have described autoantibodies to complement factor H of the IgG class in 10% of patients with aHUS but have not reported anti-factor H autoantibodies of the IgM class.

METHODS

In 186 patients with thrombotic microangiopathy clinically presented as aHUS, we searched for anti-factor H autoantibodies of the IgM class and those of the IgG and IgA classes. We used immunochromatography to purify anti-factor H IgM autoantibodies and immunoenzymatic methods and a competition assay with mapping mAbs to characterize interaction with the target protein.

RESULTS

We detected anti-factor H autoantibodies of the IgM class in seven of 186 (3.8%) patients with thrombotic microangiopathy presented as aHUS. No association was observed between anti-factor H IgM and homozygous deletions involving CFHR3-CFHR1. A significantly higher proportion of patients with bone marrow transplant-related thrombotic microangiopathy had anti-factor H IgM autoantibodies versus other patients with aHUS: three of 20 (15%) versus four of 166 (2.4%), respectively. The identified IgM autoantibodies recognize the SCR domain 19 of factor H molecule in all patients and interact with the factor H molecule, inhibiting its binding to C3b.

CONCLUSIONS

Detectable autoantibodies to factor H of the IgM class may be present in patients with aHUS, and their frequency is six-fold higher in thrombotic microangiopathy forms associated with bone marrow transplant. The autoantibody interaction with factor H's active site may support an autoimmune mechanism in some cases previously considered to be of unknown origin.

Eculizumab discontinuation in atypical haemolytic uraemic syndrome: TMA recurrence risk and renal outcomes

Background

Eculizumab modifies the course of disease in patients with atypical haemolytic uraemic syndrome (aHUS), but data evaluating whether eculizumab discontinuation is safe are limited.

Methods

Patients enrolled in the Global aHUS Registry who received ≥1 month of eculizumab before discontinuing, demonstrated haematologic or renal response prior to discontinuation and had ≥6 months of follow-up were analysed. The primary endpoint was the proportion of patients suffering from thrombotic microangiopathy (TMA) recurrence after eculizumab discontinuation. Additional endpoints included: estimated glomerular filtration rate changes following eculizumab discontinuation to last available follow-up; number of TMA recurrences; time to TMA recurrence; proportion of patients restarting eculizumab; and changes in renal function.

Results

We analysed 151 patients with clinically diagnosed aHUS who had evidence of haematologic or renal response to eculizumab, before discontinuing. Thirty-three (22%) experienced a TMA recurrence. Univariate analysis revealed that patients with an increased risk of TMA recurrence after discontinuing eculizumab were those with a history of extrarenal manifestations prior to initiating eculizumab, pathogenic variants or a family history of aHUS. Multivariate analysis showed an increased risk of TMA recurrence in patients with pathogenic variants and a family history of aHUS. Twelve (8%) patients progressed to end-stage renal disease after eculizumab discontinuation; seven (5%) patients eventually received a kidney transplant. Forty (27%) patients experienced an extrarenal manifestation of aHUS after eculizumab discontinuation.

Conclusions

Eculizumab discontinuation in patients with aHUS is not without risk, potentially leading to TMA recurrence and renal failure. A thorough assessment of risk factors prior to the decision to discontinue eculizumab is essential.

Haemoglobinuria for the early identification of aHUS relapse: data from the ItalKId-HUS Network

BACKGROUND

Atypical haemolytic uremic syndrome (aHUS) is at high risk of relapse at any time, therefore patients require lifelong monitoring. The most appropriate way to monitor patients is not yet clear. Patients could be monitored for relapse by urine dipstick testing for haemoglobinuria based on the hypothesis that thrombotic microangiopathy involving the glomerulus and associated with renal damage (like aHUS) cannot occur without haematuria.

METHODS

The aim of this retrospective study is to analyse our experience with this approach in aHUS patients who have never previously been treated, who are currently on treatment or who have discontinued C5 inhibition. The records of all aHUS patients (children and adults) managed by or referred to our Centre from January 2009 to March 2020 were included and the analysis for the presence of haemoglobinuria was restricted to the period following primary remission. A positive test was defined as haemoglobin ≥ 1 + . Patients reporting positive urine dipstick tests underwent laboratory investigations to rule in or out the diagnosis of aHUS relapse.

RESULTS

Eighty-four patients were included with 1517 determinations of haemoglobinuria during a cumulative observation period of 8904 patient-months. Haemoglobinuria for the early diagnosis of ongoing aHUS relapse shows a sensitivity of 100% and a specificity of 87.4% with a positive predictive value (PPV) of 10.5% and a negative predictive value (NPV) of 100%. The accuracy of the test was 87.6%.

CONCLUSION

Haemoglobinuria is a very sensitive and acceptably specific marker of aHUS relapse. This finding and its validation may have a positive impact on patients' quality of life and on the outcome of this life threatening disease via early diagnosis of relapse.

Is Shigatoxin 1 protective for the development of Shigatoxin 2-related hemolytic uremic syndrome in children? Data from the ItalKid-HUS Network

BACKGROUND

Shigatoxin (Stx)-producing Escherichia coli (STEC) are the most common causes of hemolytic uremic syndrome (STEC-HUS). The aim of our study is to compare the risk of developing STEC-HUS in relation to the type of Stx genes (Stx1, Stx2, or both).

METHODS

This is a prospective, observational, multicenter study involving 63 pediatric units in Northern Italy (ItalKid-HUS Network). STEC-infected children were identified within a screening program for bloody diarrhea during a 10-year period (2010-2019). Stx genes were detected by reverse dot blot or real-time PCR. After the identification of STEC infection, children were followed until diarrhea complete recovery for the possible development of STEC-HUS.

RESULTS

Of the 214 Stx-positive patients, 34 (15.9%) developed STEC-HUS. The risk of HUS in STEC-infected children with Stx1 (n: 62; 29.0%) and Stx2 (n: 97; 45.3%) was respectively 0% and 23.7%, while in patients carrying both Stx1 and Stx2 (n: 55; 25.7%), the risk was 12.7% (p: 0.001).

CONCLUSIONS

Our data confirm that Stx1 is a very rare cause of STEC-HUS and demonstrate that the risk of STEC-HUS halves in the case of Stx1+2-producing Escherichia coli infection compared with infections where Stx2 is present alone. This observation is helpful in assessing the risk of individual STEC-infected patients for the development of HUS and suggests that Stx1, in the presence of Stx2, might exert a protective role possibly by receptor competition.

Prevalence of Malnutrition Assessed by Bioimpedance Analysis and Anthropometry in Children on Peritoneal Dialysis

Objective

To evaluate the sensitivity of anthropometry and bioelectrical impedance analysis (BIA) in detecting alterations in body composition of children treated with peritoneal dialysis (PD), and to determine the prevalence of malnutrition in this population, in short- and long-term PD duration, using anthropometric and BIA-derived indices.

Patients

Eighteen children treated with automated PD (11 males, 7 females; mean age 8.7 ± 4.7 years).

Design

Eighteen patients were studied using anthropometry and BIA at the start (t0) and after 6 months (t1) of PD, 15 of these patients at 12 months (t2), and 8 at 24 months (t3) of PD. Midarm muscle circumference (MAMC), arm muscle area (AMA), and arm fat area (AFA) were calculated from anthropometric measures according to Frisancho (FrisanchoAR. New norms of upper limb fat and muscle areas for assessment of nutritional status. Am J Clin Nutr 1981; 34:2540–5.). The bioelectrical measures of resistance (R) and reactance (Xc) were obtained directly from the impedance signal; phase angle (PA) and distance (D) were calculated using mathematical formulas. Nutritional status was assessed by anthropometric measurements and BIA-derived indices, expressed as standard deviation scores (SDS), and by a score system based on BIA and anthropometric parameters. The percentage of children with values of anthropometric and BIA-derived indices below the 3rd percentile or between the 3rd and 25th percentiles, and the percentage of children with scores of 7 – 12 and 4 – 6 were calculated in order to detect patients with severe or moderate derangement of nutritional status.

Results

The mean SDS values of Xc, PA, and D significantly improved ( p = 0.05, p = 0.001, p = 0.02) during the first 6 months of PD and remained almost stable during the following months. The SDS values of the anthropometric indices were less compromised than those of the BIA-derived indices, particularly at the start of dialysis. By 6 months, the percentages of children with values of BIA and anthropometric indices below the 3rd percentile had decreased. The percentages of patients with moderate and severe derangement of BIA and anthropometric indices remained substantially unchanged after 12 months. However, at 24 months, the percentage of patients with moderate derangement of BIA indices increased. All these findings were confirmed by the nutritional score system.

Conclusion

BIA is more sensitive than anthropometry in detecting alterations in body composition of children on PD. The prevalence of malnutrition, high at the commencement of PD, decreases during the first year of treatment but not over the long term.

The Italian Registry of Pediatric Chronic Peritoneal Dialysis: A Ten-Year Experience with Chronic Peritoneal Dialysis Catheters

Objective

To analyze the data from 347 peritoneal catheters implanted in 249 pediatric patients aged ≤ 15 years at start of chronic peritoneal dialysis (CPD).

Design

Restrospective study of the data collected between 1986 and 1995, in 20 dialysis centers, from the Italian Registry of Pediatric Chronic Peritoneal Dialysis. Data collection for each pediatric catheter included: catheter type, site and technique of insertion, complications, duration, and reason for removal or replacement.

Results

Fifty catheters were inserted in patients under 2 years of age, 50 in patients aged 2 5 years and 247 in patients over 5 years of age. Catheter types included 307 (88.5%) Tenckhoff (286 double cuff, 21 single cuff) and 40 (11.5%), double-cuff, Valli-type catheters. All catheters were surgically implanted and omentectomy was performed in 83.5% of cases; the entry-site was in the midline in 136 cases (39.2%) and paramedian in 211 (60.8%). During 6076 CPD months we observed 274 catheter related complications: 182 catheter infections (exit-site and/or tunnel infection), 23 leakages, 19 obstructions, 19 cuff-extrusions, 14 dislocations, 6 hemoperitoneum, 10 other (incidence of one complication every 21.8 dialysis months). A significant reduction of catheter-related complications occurred in the last five years, compared with the first 5 years. One hundred and six catheters were removed due to catheter-related causes: infection (83 cases), obstruction (11), dislocation (4), outer-cuff extrusion (3), leakage (2), bowel incarceration (2), and bowel infarction (1). Catheter survival was 72.2% at 12 months, 52.3% at 24 months, 32.8% at 36 months, and 25.7% at 48 months. Significantly lower catheter survival was found in younger children (0 2 years) compared with two other age groups (2 5 years, and > 5 years). No significant correlation was found between catheter survival and catheter entry-site (midline vs paramedian).

Conclusions

Catheter-related infections were confirmed to be the most common complication and most frequent cause of peritoneal catheter removal. In addition, catheter survival rate was worse in younger children, indicating that more effort should be made to improve peritoneal catheter survival particularly in this age group.

A Novel Objective Nutritional Score for Children on Chronic Peritoneal Dialysis

Objectives

To establish a novel nutritional score based on a series of objective parameters capable of detecting protein-calorie malnutrition in children being treated with chronic peritoneal dialysis (CPD), to test the score in a healthy pediatric population, and to apply it to children on CPD to evaluate their nutritional status.

Study Population

264 healthy school children (mean age 8.69 ± 3.26 years, range 3.05 – 14.98 years) and 29 patients treated with CPD for 1.75 ± 1.02 years (mean age 10.54 ± 6.28 years, range 2.8 – 15.24 years).

Methods

Nutritional status was evaluated by means of three sets of measurements: anthropometric (A1 and A2) and bioimpedance analysis (BIA) measurements. Anthropometry included two sets of measures: set A1 consisted of height (H), weight (W), and body mass index (BMI); set A2 consisted of midarm muscle circumference (MAMC), arm muscle area (AMA), and arm fat area (AFA). The BIA measurements included reactance, phase angle, and distance. All parameters are expressed as standard deviation scores (SDS). Tanner's, Rolland–Cachera's, and Frisancho's data were used as references for H, W, BMI, MAMC, AMA, and AFA; personal data obtained from 551 healthy boys and girls were used for the BIA indices. The nine anthropometry and BIA parameters were given scores of 1 to 5: 5 = > 0 SDS, 4 = ≤ 0 and > –1 SDS, 3 = ≤ –1 and > –2 SDS, 2 = ≤ –2 and > –3 SDS, and 1 = ≤ –3 SDS. Average scores were established for each of A1, A2, and BIA, and then summed to obtain the anthropometry–BIA nutrition (ABN) score. To establish the cutoff value between normal nutritional status and malnutrition, the method was first applied to the 264 healthy children; distribution percentiles were calculated for each area score and the ABN score. The ABN score corresponding to the 3rd percentile was considered the limit of normality and then applied three times to the 29 children on CPD, for a total of 87 nutritional assessments.

Results

The score corresponding to the 3rd percentile in the population of healthy children was 10.33. Among the CPD-treated children, 41.4% of the ABN scores were higher than 10.33 (indicating a state of normal nutrition) and 58.6% were lower (indicating various degrees of malnutrition). Severe malnutrition was found in only 1.1% of the cases. The values of all nine A1, A2, and BIA parameters, as well as serum albumin levels, were significantly higher in patients with an ABN score > 10.33 than in those with a score < 10.33.

Conclusion

The ABN score is a simple and objective method of assessing, in clinical practice, the nutritional status of children on CPD.

Particulate Shiga Toxin 2 in Blood is Associated to the Development of Hemolytic Uremic Syndrome in Children

Hemolytic uremic syndrome (HUS), the leading cause of acute renal failure in children (< 3 years), is mainly related to Shiga toxins (Stx)-producing Escherichia coli (STEC) infections. STEC are confined to the gut resulting in hemorrhagic colitis, whereas Stx are delivered in blood to target kidney and brain, with unclear mechanisms, triggering HUS in 5 to 15% of infected children. Stx were found on circulating cells, free in sera (soluble Stx) or in blood cell-derived microvesicles (particulate Stx), whereby the relationship between these forms of circulating toxins is unclear. Here, we have examined 2,846 children with bloody diarrhea and found evidence of STEC infection in 5%. Twenty patients were enrolled to study the natural course of STEC infections before the onset of HUS. In patients, Stx were found to be associated to circulating cells and/or free and functionally active in sera. In most children, Stx were bound to neutrophils when high amounts of toxins were found in feces. Time-course analysis showed that Stx increased transiently in patients' sera while the decrease of toxin amount on leukocytes was observed. Notably, patients who recovered (85%) displayed different settings than those who developed HUS (15%). The distinctive feature of the latter group was the presence in blood of particulate Stx2 (Stx2 sedimented at g-forces corresponding to 1 μm microvesicles) the day before diagnosis of HUS, during the release phase of toxins from circulating cells. This observation strongly suggests the involvement of blood cell-derived particulate Stx2 in the transition from hemorrhagic colitis to HUS.

[HELLP syndrome and hemolytic uremic syndrome during pregnancy: two disease entities, same causation. Case report and literature review]

Thrombotic microangiopathies (TMA) are a group of diseases that can complicate pregnancy and threaten the lives of both the mother and the fetus. Several conditions can lead to TMA, including thrombotic thrombocytopenic purpura (TTP), HELLP syndrome and hemolytic uremic syndrome (HUS). We describe the case of a 39-year-old woman who presented a HELLP syndrome in the immediate postpartum period. The patient had acute kidney injury (AKI), increased LDH, unmeasurable haptoglobin levels and hypocomplementemia. Her ADAMTS13 value was normal, thus ruling out TTP. Shiga toxin tests were negative, so HUS associated with E. coli was also ruled out. HELLP syndrome and atypical hemolytic-uremic syndrome (aHUS) remained the most probable diagnosis. In the days following childbirth, the patient's transaminase and bilirubin levels normalized while the anemia persisted, as did the AKI, resulting in the institution of dialysis treatment. A diagnosis of aHUS was made and therapy with eculizumab was started. The patient's blood counts progressively improved, urine output was restored, her indices of renal function also concomitantly improved and dialysis was interrupted. A rash appeared after the third administration of eculizumab and the treatment was suspended. The patient is currently being followed up and has not relapsed. At thirteen months after delivery her renal function is normal as are her platelet counts, LDH, haptoglobin levels and proteinuria. Tests for mutations in the genes that regulate complement activity were negative. We believe that childbirth triggered the HELLP syndrome, which in turn brought about and sustained the HUS. In fact, the patient's liver function improved right after delivery, while her kidney injury and hemolysis persisted, and she also had an excellent response to eculizumab. To our knowledge, no other cases of HELLP syndrome associated with haemolytic uremic syndrome during pregnancy have been reported in literature, nor have cases in which treatment with eculizumab was limited to only three administrations.

A simple prognostic index for Shigatoxin-related hemolytic uremic syndrome at onset: data from the ItalKid-HUS network

Shigatoxin Escherichia coli-related hemolytic uremic syndrome (eHUS) is a severe thrombotic microangiopathy (TMA) burdened by life-threatening complications and long-term sequelae. Since hemoconcentration is associated with worse outcome, we tried to develop a reliable and easy-to-calculate index for predicting complications and sequelae based on hemoglobin (Hb) at presentation. The first laboratory examinations with signs of TMA in eHUS patients were analyzed in relation to the outcomes with the receiver operating characteristic curves and their areas under the curve (AUC) for Hb and creatinine (sCr). A total of 197 eHUS patients were identified of whom 24% did not have anemia at presentation. Hb level was the best predictor of a poor outcome (AUC 0.67) but the combination of Hb with sCr, in the formula [(Hb in g/dL + (sCr in mg/dL × 2)], showed an even better AUC of 0.75. The described scoring system was also strongly associated and predictive of all complications and health care needs (8% of patients with scoring > 13 died or entered a permanent vegetative state compared with 0% of those with ≤ 13).Conclusion: The presented score is a simple and early predictor of both short- and long-term outcomes and identifies patients who should undergo rapid volume expansion to counteract hemoconcentration, the spreading of microvascular thrombosis, and the consequent increased organ damage. What is Known: • In eHUS, hemoconcentration is associated with worse short- and long-term outcome. • A prognostic index to identify patients at higher risk for complications at presentation is not available. What is New: • We developed a simple and early prognostic index for eHUS outcome with the combination of Hb and sCr at onset, in the following formula [(Hb in g/dL + (sCr in mg/dL × 2)]. • The proposed HUS Severity Score can promptly identify patients with good outcome and those with high risk of worse short- and long-term outcome.

Soluble Toll-Like Receptor 4 Impairs the Interaction of Shiga Toxin 2a with Human Serum Amyloid P Component

Shiga toxin 2a (Stx2a) is the main virulence factor produced by pathogenic Escherichia coli strains (Stx-producing E. coli, STEC) responsible for hemorrhagic colitis and the life-threatening sequela hemolytic uremic syndrome in children. The toxin released in the intestine by STEC targets the globotriaosylceramide receptor (Gb3Cer) present on the endothelial cells of the brain and the kidney after a transient blood phase during which Stx2a interacts with blood components, such as neutrophils, which, conversely, recognize Stx through Toll-like receptor 4 (TLR4). Among non-cellular blood constituents, human amyloid P component (HuSAP) is considered a negative modulating factor that specifically binds Stx2a and impairs its toxic action. Here, we show that the soluble extracellular domain of TLR4 inhibits the binding of Stx2a to neutrophils, assessed by indirect flow cytometric analysis. Moreover, by using human sensitive Gb3Cer-expressing cells (Raji cells) we found that the complex Stx2a/soluble TLR4 escaped from capture by HuSAP allowing the toxin to target and damage human cells, as assayed by measuring translation inhibition, the typical Stx-induced functional impairment. Thus, soluble TLR4 stood out as a positive modulating factor for Stx2a. In the paper, these findings have been discussed in the context of the pathogenesis of hemolytic uremic syndrome.

Serum creatinine during physiological perinatal dehydration may estimate individual nephron endowment

It is well known that the nephron endowment of healthy subjects is highly variable and that individual nephron mass has potentially important implications both in health and disease. However, nephron count is technically impossible in living subjects. Based on the observation of an increase in serum creatinine (sCr) in otherwise healthy newborns with solitary kidney during the physiological perinatal dehydration, we hypothesized that perinatal sCr might be helpful in identifying healthy subjects with a reduced nephron mass. In the framework of a study on blood pressure in babies (NeoNeph), sCr of normal Caucasian neonates was determined 48-96 h after birth and their association with a family history of arterial hypertension (AH) was analyzed. SCr was determined in 182 normal newborns (90 males) at a mean of 61 ± 8 h after birth (range 46-82). Newborns with paternal AH had a higher mean sCr (0.97 + 0.28 mg/dL) then newborns without paternal AH (0.73 + 0.28 mg/dL; p = 0.006). No differences in mean sCr were found in relation with mother or grandparent's history of AH.

CONCLUSION

The association between parental AH and high sCr during perinatal dehydration supports the hypothesis that the latter is a promising tool for identifying normal subjects with a reduced nephron mass with potential important implications in prevention and in understanding the individual outcome of renal and extrarenal diseases (including AH). What is Known: • Nephron endowment of healthy subjects is highly variable and individual nephron mass has potentially important implications both in health and disease however nephron count is not feasible in living subjects. What is New: • Serum creatinine during perinatal dehydration is a possible biomarker for identifying normal subjects with a reduced nephron mass.

Clinical and genetic predictors of atypical hemolytic uremic syndrome phenotype and outcome

Atypical hemolytic uremic syndrome (aHUS) is a rare, genetic, life-threatening disease. The Global aHUS Registry collects real-world data on the natural history of the disease. Here we characterize end-stage renal disease (ESRD)-free survival, the rate of thrombotic microangiopathy, organ involvement and the genetic background of 851 patients in the registry, prior to eculizumab treatment. A sex-specific difference was apparent according to age at initial disease onset as the ratio of males to females was 1.3:1 for childhood presentation and 1:2 for adult presentation. Complement Factor I and Membrane Cofactor Protein mutations were more common in patients with initial presentation as adults and children, respectively. Initial presentation in childhood significantly predicted ESRD risk (adjusted hazard ratio 0.55 [95% confidence interval 0.41-0.73], whereas sex, race, family history of aHUS, and time from initial presentation to diagnosis, did not. Patients with a Complement Factor H mutation had reduced ESRD-free survival, whereas Membrane Cofactor Protein mutation was associated with longer ESRD-free survival. Additionally extrarenal organ manifestations occur in 19%-38% of patients within six months of initial disease presentation (dependent on organ). Thus, our real-world results provide novel insights regarding phenotypic variables and genotypes on the clinical manifestation and progression of aHUS.

Management and outcomes of childhood Goodpasture's disease

BackgroundIn an attempt to improve knowledge about childhood Goodpasture's disease, we performed a retrospective analysis of patients with Goodpasture's disease from several pediatric nephrology centers.MethodsWe analyzed the responses to 27 questions that elicited information about the following: incidence, demographics, patient history and clinical presentation, diagnostics performed, acute and chronic therapy, course of disease, and outcome.ResultsGoodpasture's disease, which is extremely rare in this age group, may manifest in 2-year-old toddlers and does not typically present with pulmonary findings before puberty. Goodpasture's disease has a poor outcome with more than 50% of patients progressing to end-stage renal disease. No deaths were reported in this cohort, and renal improvement was observed in children with severe biopsy findings who required renal replacement therapy during the acute phase.ConclusionThe present investigation gives detailed information about childhood Goodpasture's disease under real-life conditions and reveals that very few pediatric cases have been reported. Nearly 50% of children progressed to end-stage renal disease. However, long-term outcome in children might be better than in adults. Aggressive immunosuppressive therapy might be necessary for all affected children, even in patients who require renal replacement therapy or have severe biopsy findings.

Complement functional tests for monitoring eculizumab treatment in patients with atypical hemolytic uremic syndrome: an update

BACKGROUND

Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy (TMA) characterized by platelet consumption, hemolysis, and organ damage. Eculizumab (ECU), a humanized antibody that blocks complement activity, has been successfully used in aHUS, but the best treatment schedule is not yet clear.

METHODS

Here, we report our experience with ECU maintenance treatment and the interval between subsequent doses being extended based on global classical complement pathway (CCP) activity aimed at <30% for maintaining aHUS into remission.

RESULTS

We report on 38 patients with aHUS, 13 children, 21 female, with a median age of 25.0 years (range 0.5-60) at disease onset treated with ECU standard schedule for a median of 2.6 months (range 0.4-24.6). Once stable TMA remission was obtained, the interval between ECU doses was extended based on complement function, with a target CCP activity of <30%. With this approach, 22 patients regularly receive ECU infusion every 28 days and 16 every 21. During a median observation period on ECU, an extended interval of 26.9 months (range 0.8-80.9), with a cumulative observation period of 1,208 months, none of the patients relapsed.

CONCLUSION

Monitoring complement activity allows a safe reduction in the frequency of ECU administration in aHUS while keeping the disease in remission.

Exome-wide Association Study Identifies GREB1L Mutations in Congenital Kidney Malformations

Renal agenesis and hypodysplasia (RHD) are major causes of pediatric chronic kidney disease and are highly genetically heterogeneous. We conducted whole-exome sequencing in 202 case subjects with RHD and identified diagnostic mutations in genes known to be associated with RHD in 7/202 case subjects. In an additional affected individual with RHD and a congenital heart defect, we found a homozygous loss-of-function (LOF) variant in SLIT3, recapitulating phenotypes reported with Slit3 inactivation in the mouse. To identify genes associated with RHD, we performed an exome-wide association study with 195 unresolved case subjects and 6,905 control subjects. The top signal resided in GREB1L, a gene implicated previously in Hoxb1 and Shha signaling in zebrafish. The significance of the association, which was p = 2.0 × 10^-5 for novel LOF, increased to p = 4.1 × 10^-6 for LOF and deleterious missense variants combined, and augmented further after accounting for segregation and de novo inheritance of rare variants (joint p = 2.3 × 10^-7). Finally, CRISPR/Cas9 disruption or knockdown of greb1l in zebrafish caused specific pronephric defects, which were rescued by wild-type human GREB1L mRNA, but not mRNA containing alleles identified in case subjects. Together, our study provides insight into the genetic landscape of kidney malformations in humans, presents multiple candidates, and identifies SLIT3 and GREB1L as genes implicated in the pathogenesis of RHD.

Role of climate in the spread of shiga toxin-producing Escherichia coli infection among children

Haemolytic-uraemic syndrome (HUS) is a rare disease mainly affecting children that develops as a complication of shiga toxin-producing Escherichia coli (STEC) infection. It is characterised by acute kidney injury, platelet consumption and mechanical destruction of red blood cells (haemolysis). In order to test the working hypothesis that the spread of the infection is influenced by specific climatic conditions, we analysed all of the identified cases of infection occurring between June 2010 and December 2013 in four provinces of Lombardy, Italy (Milano, Monza Brianza, Varese and Brescia), in which a STEC surveillance system has been developed as part of a preventive programme. In the selected provinces, we recorded in few days a great number of cases and clusters which are unrelated for spatially distant or for the disease are caused by different STEC serotypes. In order to investigate a common factor that favoured the onset of infection, we have analysed in detail the weather conditions of the areas. The daily series of temperature, rain and relative humidity were studied to show the common climate peculiarities whilst the correlation coefficient and the principal component analysis (PCA) were used to point out the meteorological variable, maximum temperature, as the principal climate element in the onset of the infection. The use of distributed lag non-linear models (DLNM) and the climate indices characterising heat waves (HWs) has allowed to identify the weather conditions associated with STEC infection. The study highlighted a close temporal correlation between STEC infection in children and the number, duration and frequency of heat waves. In particular, if the maximum temperature is greater than 90th percentile, days classified as very hot, for 3 or more consecutive days, the risk of infection is increasing.

Acquired Complement Regulatory Gene Mutations and Hematopoietic Stem Cell Transplant-Related Thrombotic Microangiopathy

Hematopoietic stem cell transplant-related thrombotic microangiopathy (HSCT-TMA) is a severe complication whose pathophysiology is unknown. We describe 6 patients in which the disease was associated with complement regulatory gene abnormalities received from their respective donors. It is suggested that mutated and transplanted monocyte-derived cells are responsible for production of abnormal proteins, complement dysregulation, and, ultimately, for the disease. This observation might have important drawbacks as far as HSCT-TMA pathophysiology and treatment are concerned.

FilmArray™ GI panel performance for the diagnosis of acute gastroenteritis or hemorragic diarrhea

Background

Acute gastroenteritis is a common cause of morbidity and mortality in humans worldwide. The rapid and specific identification of infectious agents is crucial for correct patient management. However, diagnosis of acute gastroenteritis is usually performed with diagnostic panels that include only a few pathogens. In the present bicentric study, the diagnostic value of FilmArray™ GI panels was assessed in unformed stool samples of patients with acute gastroenteritis and in a series of samples collected from pediatric patients with heamorragic diarrhea. The clinical performance of the FilmArray™ gastrointestinal (GI) panel was assessed in 168 stool samples collected from patients with either acute gastroenteritis or hemorragic diarrhea. Samples showing discordant results between FilmArray and routine methods were further analyzed with an additional assay.

Results

Overall, the FilmArray™ GI panel detected at least one potential pathogen in 92/168 (54.8%) specimens. In 66/92 (71.8%) samples, only one pathogen was detected, while in 26/92 (28.2%) multiple pathogens were detected.

The most frequent pathogens were rotavirus 13.9% (22/168), Campylobacter 10.7% (18/168), Clostridium difficile 9.5% (16/168), and norovirus 8.9% (15/168). Clostridium difficile was identified only in patients with acute gastroenteritis (p < 0.01), while STEC was detected exclusively in patients with hemorragic diarrhea (p < 0.01). In addition, Campylobacter spp., Salmonella spp., EPEC and E. coli producing Shiga-like toxin were more frequently detected in patients with hemorragic diarrhea (p < 0.05). The overall percent agreement calculated in samples was 73.8% and 65.5%, while 34.5% were discordant. After additional confirmatory analyses, the proportion of discordant samples decreased to 7.7%. Rotavirus and astrovirus were the most frequently unconfirmed pathogens.

Conclusion

In conclusion, the FilmArray™ GI panel has proved to be a valuable new diagnostic tool for improving the diagnostic efficiency of GI pathogens.

[Complement factor B mutation in atypical hemolytic uremic syndrome. Rare cause of rare disease]

Hemolytic uremic syndrome (HUS) is a rare disease characterized by microangiopathic hemolysis, platelet consumption and multiple organ failure with predominant renal involvement. In the most of cases (85-90%), it is associated with enteric infection due to Shiga-toxin or verocytotoxin (STEC-VTEC)-producer Escherichia coli. Rarely, in about 10-15% of cases, HUS develops in the presence of a disorder of alternative complement pathway regulation and it is defined atypical (aHUS). We describe the case of a 65-year-old man who came to our attention with a clinical presentation of aHUS and a clinical course characterized by rapidly progressive acute renal failure (ARF), which required renal replacement treatments, and by a stable clinical picture of hematological impairment as a marker of a non-severe and self-limiting form. The clinical and laboratory course allowed us not to perform specific therapies such as plasma exchange and/or block of the complement with eculizumab. Less than two weeks after hospital admission, there was a gradual recovery of renal function with spontaneous diuresis and hematological remission. Genetic screening has revealed a heterozygous mutation in the complement factor B (CFB) that is not described in the literature and therefore not yet characterized in the genotype/phenotype correlation, also for the extreme rarity of the forms associated with CFB alteration. In conclusion, the presence of a new mutation in the CFB, such as the one described in our case, is probably associated with the development of aHUS but has not led to a poor prognosis, as generally reported in the literature for known variants of the CFB.

Mutational Spectrum of CYP24A1 Gene in a Cohort of Italian Patients with Idiopathic Infantile Hypercalcemia

BACKGROUND/AIMS

Loss-of-function mutations in the CYP24A1 gene, which encodes the vitamin D-24 hydroxylase, have been recognized as a cause of elevated 1,25-dihydroxyvitamin D concentrations, hypercalcemia, hypercalciuria, nephrocalcinosis and nephrolithiasis in infants and adults. As only a case report describing 2 adult patients has been reported in Italian population, we report here the mutation analysis of CYP24A1 gene in an Italian cohort of 12 pediatric and adult patients with idiopathic infantile hypercalcemia (IIH).

METHODS

We performed mutational screening of CYP24A1 gene in a cohort of 12 Italian patients: 8 children with nephrocalcinosis, hypercalcemia and PTH levels <10 pg/ml and 4 adult patients with nephrolithiasis, mild hypercalcemia and PTH levels <10 pg/ml from 11 unrelated Italian families. Clinical and biochemical data were collected. Genomic DNA was extracted from peripheral blood leucocytes using standard methods, and whole coding sequence of CYP24A1 gene was analysed in all patients and family members by polymerase chain reaction and direct sequencing. The potential pathogenicity of the newly identified missense mutations was evaluated by 3 different in silico approaches (Sorting Intolerant from Tolerant, Polyphen and Mutation Taster) and by comparative analysis in 14 different species using ClustalW software.

RESULTS

CYP24A1 bi-allelic mutations were found in 8 individuals from 7 Italian families (7/11; 64%). Overall, 6 different CYP24A1 mutations, including one small deletion (p.Glu143del), 4 missense mutations (p.Leu148Pro; p.Arg396Trp; p.Pro503Leu; p.Glu383Gln) and one nonsense mutation (p.Tyr220*) were identified. Two out of 6 mutations (p.Tyr220* and p.Pro503Leu) were not previously described. Moreover, a new CYP24A1 variant was identified by genetic screening of asymptomatic controls.

CONCLUSION

To the best of our knowledge, this is the first report of a CYP24A1 molecular analysis performed in an Italian cohort of adult and pediatric Italian patients. This study (1) confirms that CYP24A1 plays a causal role in some but not all cases of IIH (64%); (2) expands the spectrum of known CYP24A1 pathogenic mutations; (3) describes 2 hotspots detected in 50% of all Italian cases; and (4) emphasizes the importance of recognition and genetic diagnosis of CYP24A1 defects in infantile as well as adult hypercalcemia.

[Efficacy of eculizumab in a case of pregnancy-associated aHUS]

Pregnancy-associated thrombotic microangiopathy (TMA) is a rare condition, but it is burdened by a significant perinatal and maternal morbidity as well as mortality. We describe the case of a 33-year-old woman, who developed a TMA at the 36th week of gestation characterized by increased LDH, haptoglobin consumption, schistocytes, thrombocytopenia and acute renal failure requiring dialysis. There were not gestational hypertension nor proteinuria until the day of hospitalization. ADAMTS 13 deficiency was ruled out and the patient did not have diarrhea. She was initially treated with caesarean section, plasma infusion and plasmapheresis with no benefit. Five days after the onset of TMA, a temptative diagnosis of atypical uremic syndrome (aHUS) was made and the patient was switched to eculizumab. Antibiotic prophylaxis and anti-meningococcal A,B, C, W135 and Y vaccination was performed. TMA rapidly resolved and renal function completely recovered. The newborn had a normal perinatal course. A complement dysregulation was ruled out by testing for mutations on CFH, CFHR3-R1, CFI, MCP, CFB, C3 and for anti CFH antibodies. In conclusion the differential diagnosis of aHUS with HELLP syndrome is often not straightforward. The severity and persistence of TMA, the high mortality associated to peripartum TMA and the risk for irreversible kidney failure require an early therapeutic decision as to the use of eculizumab.

Posterior reversible encephalopathy syndrome after kidney transplantation in pediatric recipients: Two cases

PRES is a neuro-clinical and radiological syndrome that can result as a consequence of several different conditions including hypertension, fluid overload, and immunosuppressive treatment. Herein, we report two children who received kidney and combined liver-kidney transplantation as treatment for renal hypodysplasia associated with bilateral vesico-ureteral reflux and methylmalonic acidemia, respectively. Early after surgery (seven and 10 days), both patients presented with hypertension and seizures. The patients' immunosuppressive regimen included steroid and calcineurin inhibitors (tacrolimus and cyclosporine, respectively) and basiliximab and one with anti-IL2 receptor. In both cases, the imaging strongly supported the diagnosis of PRES. In details, the CT scan showed hypodensities in the posterior areas of the brain, and brain MRI demonstrated parieto-occipital alterations indicative of vasogenic edema. Treatment with calcineurin inhibitors was temporally discontinued and restarted at lower dosage; arterial hypertension was treated with Ca-channel blockers. Both children fully recovered without any neurological sequels. In conclusion, in children undergoing solid organ transplantation, who develop neurological symptoms PRES, should be carefully considered in the differential diagnosis and once the diagnosis is ruled in, we recommend strict arterial blood pressure control and adjustment or withholding of calcineurin inhibitor therapy should be considered based upon blood levels.