Understanding thrombotic microangiopathies in children

A Moderate Decrease in ADAMTS13 Activity Correlates with the Severity of STEC-HUS

Atypical hemolytic uremic syndrome (HUS) develops as a result of damage to the endothelium of microvasculature vessels by Shiga toxin produced by enterohemorrhagic Escherichia coli (STEC-HUS). STEC-HUS remains the leading cause of acute kidney injury (AKI) in children aged 6 months to 5 years. The pathomorphological essence of the disease is the development of thrombotic microangiopathy (TMA). One of the key causes of TMA is an imbalance in the ADAMTS13-von Willebrand factor (vWF)-platelet system. The goal of the work was to clarify the role of a moderate decrease in ADAMTS13 activity in the pathogenesis of STEC-HUS. The activity of ADAMTS13 was determined in 138 children (4 months-14.7 years) in the acute period of STEC-HUS and the features of the course of the disease in these patients were analyzed. The study revealed a decrease in the activity and concentration of ADAMTS13 in 79.8% and 90.6% of patients, respectively. Measurements of von Willebrand factor antigen content and the activity of von Willebrand factor in the blood plasma of part of these patients were carried out. In 48.6% and 34.4% of cases, there was an increase in the antigen concentration and the activity of the Willebrand factor, respectively. Thrombocytopenia was diagnosed in 97.8% of children. We have demonstrated that moderately reduced ADAMTS13 activity correlates with the risk of severe manifestations of STEC-HUS in children; the rate of developing multiple organ failure, cerebral disorders, pulmonary edema, and acute kidney injury with the need for dialysis increases. It is assumed that reduction in ADAMTS13 activity may serve as a predictor of disease severity.

Treatment Challenges of Acquired Thrombotic Thrombocytopenic Purpura in Pediatric Patients From a Low-Income Country

This study presents a comprehensive analysis of two cases of acquired thrombotic thrombocytopenic purpura (aTTP) observed in pediatric patients from a low-income country. In the instances described, both patients underwent a treatment regimen involving plasma exchange and immunosuppressive therapy conducted without the use of caplacizumab. Caplacizumab, an approved drug for adults known for its limited availability and high cost, has exhibited efficacy in reducing response time and recurrence frequency in aTTP cases. This approach resulted in significant clinical improvement and eventual remission of symptoms in one of the cases. These cases underscore the urgent necessity for a more inclusive approach in national health programs and international treatment guidelines. Specifically, there is a call to expand the existing comprehensive treatment algorithms to accommodate countries lacking access to caplacizumab. This adaptation aims to ensure the availability of suitable and effective treatment options for aTTP patients in regions facing limited pharmaceutical accessibility.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Thrombotic microangiopathy in children

The syndrome of thrombotic microangiopathy (TMA) is a clinical-pathological entity characterized by microangiopathic hemolytic anemia, thrombocytopenia, and end organ involvement. It comprises a spectrum of underlying etiologies that may differ in children and adults. In children, apart from ruling out shigatoxin-associated hemolytic uremic syndrome (HUS) and other infection-associated TMA like Streptococcus pneumoniae-HUS, rare inherited causes including complement-associated HUS, cobalamin defects, and mutations in diacylglycerol kinase epsilon gene must be investigated. TMA should also be considered in the setting of solid organ or hematopoietic stem cell transplantation. In this review, acquired and inherited causes of TMA are described with a focus on particularities of the main causes of TMA in children. A pragmatic approach that may help the clinician tailor evaluation and management is provided. The described approach will allow for early initiation of treatment while waiting for the definitive diagnosis of the underlying TMA.

[Thrombotic Microangiopathy (TMA) after Gene Replacemant Therapy (GRT) due to Spinal Muscular Atrophy: Case Summary and Recommendations for Treatment]

INTRODUCTION

5q-associated spinal muscular atrophy is one of the most severe and common genetic diseases. In the last few years, innovative methods of therapy have been developed based on SMN2 gene modification, such as splicing, or replacement of the damaged SMN1 gene (gene replacement therapy, GRT). GRT is known to be accompanied by off target effects like temporary elevation of liver and cardiac enzymes usually without serious clinical relevance. We report a 4-year-old girl suffering from thrombotic microangiopathy (TMA) after GRT due to 5q- SMA.

CASE SUMMARY

A 4-year-old girl developed TMA indicated by haemolytic anemia and thrombocytopenia in conjunction with renal failure 7 days after GRT with onasemnogene abeparvovec. The latter was characterized by a rise in serum creatinine, oliguria, hypertension, protein- and haematuria, and oedema. The patient was started on eculizumab and antihypertensives resulting in normalization of haemolytic activity, platelet count, kidney function and blood pressure within one week.

RECOMMENDATION AND CONCLUSION

SMA patients receiving GRT should undergo close monitoring for early detection of TMA. Adequate measures for TMA including eculizumab or plasmapheresis as well as renal replacement therapy should be available without delay in order to avoid progressive kidney disease or other severe complications in these patients. Careful follow-up including assessment of proteinuria and blood pressure is recommended since patients may require antihypertensive/nephroprotective treatment to avoid chronic kidney disease in later life. Therefore, GRT in SMA patients should only be performed at centers with neuropediatric and paediatric nephrology expertise.

[Recurrent thrombocytopenia with hemolytic anemia in a boy aged 3 years]

A boy, aged 3 years and 8 months, had recurrent thrombocytopenia with hemolytic anemia for more than 3 years. The physical examination showed no enlargement of the liver, spleen, and lymph nodes or finger deformities. Laboratory results showed a negative result of the direct antiglobulin test, normal coagulation function, and increases in bilirubin, lactate dehydrogenase and reticulocytes. The results of von Willebrand factor-cleaving protease ADAMTS13 activity assay showed extreme deficiency, and antibody assay showed negative ADAMTS13 inhibitory autoantibodies. Next-generation sequence showed compound heterozygous mutation in the ADAMTS13 gene. The boy was diagnosed with congenital thrombotic thrombocytopenic purpura. This disease may be easily misdiagnosed as Evans syndrome and is difficult to diagnose in clinical practice. The child had developed the disease since birth, but it took 3 years to make a confirmed diagnosis. Therefore, congenital thrombotic thrombocytopenic purpura should be considered for children with jaundice at birth, recurrent thrombocytopenia with hemolytic anemia, and negative results of the direct antiglobulin test. The detection of ADAMTS13 activity and ADAMTS13 inhibitory autoantibodies should be performed as soon as possible for a definite diagnosis, and gene detection should be performed to make a confirmed diagnosis when necessary.

[Recurrent thrombocytopenia with hemolytic anemia in a boy aged 3 years]

A boy, aged 3 years and 8 months, had recurrent thrombocytopenia with hemolytic anemia for more than 3 years. The physical examination showed no enlargement of the liver, spleen, and lymph nodes or finger deformities. Laboratory results showed a negative result of the direct antiglobulin test, normal coagulation function, and increases in bilirubin, lactate dehydrogenase and reticulocytes. The results of von Willebrand factor-cleaving protease ADAMTS13 activity assay showed extreme deficiency, and antibody assay showed negative ADAMTS13 inhibitory autoantibodies. Next-generation sequence showed compound heterozygous mutation in the ADAMTS13 gene. The boy was diagnosed with congenital thrombotic thrombocytopenic purpura. This disease may be easily misdiagnosed as Evans syndrome and is difficult to diagnose in clinical practice. The child had developed the disease since birth, but it took 3 years to make a confirmed diagnosis. Therefore, congenital thrombotic thrombocytopenic purpura should be considered for children with jaundice at birth, recurrent thrombocytopenia with hemolytic anemia, and negative results of the direct antiglobulin test. The detection of ADAMTS13 activity and ADAMTS13 inhibitory autoantibodies should be performed as soon as possible for a definite diagnosis, and gene detection should be performed to make a confirmed diagnosis when necessary.

Thrombotic Microangiopathy Following Onasemnogene Abeparvovec for Spinal Muscular Atrophy: A Case Series

Spinal muscular atrophy is treated with onasemnogene abeparvovec, which replaces the missing survival motor neuron 1 gene via an adeno-associated virus vector. As of July 1, 2020, we had identified 3 infants who developed thrombotic microangiopathy following onasemnogene abeparvovec. Early recognition and treatment of drug-induced thrombotic microangiopathy may lessen mortality and morbidity.

Coronavirus 229E with Rhinovirus co-infection causing severe acute respiratory distress syndrome with thrombotic microangiopathy and death during Covid-19 pandemic: lessons to be learnt

We report on a 3-month old infant male who had a seven-days history of fever and rhinorrhea associated with wheezing prior to his death, during the Covid-19 pandemic. Viral testing for Covid-19 (SARS-CoV-2) was negative but was positive for Coronavirus 229E and RP Human Rhinovirus. The pulmonary histological examination showed diffuse alveolar damage along with thrombotic microangiopathy affecting alveolar capillaries. Also, thrombotic microangiopathy was evident in the heart, lungs, brain, kidneys and liver. Thrombotic microangiopathy is a major pathologic finding in Acute Respiratory Distress Syndrome and in the multiorgan failure. This is the first report that illustrates thrombotic microangiopathy occurring in lung, heart, liver, kidney and brain in Acute Respiratory Distress Syndrome with Coronavirus 229E with Rhinovirus co-infection. The clinical presentation and pathological findings in our case share common features with Covid-19.

Atypical hemolytic uremic syndrome in Brazil: clinical presentation, genetic findings and outcomes of a case series in adults and children treated with eculizumab

Background

Atypical hemolytic uremic syndrome (aHUS) is characterized by microangiopathic hemolytic anemia, thrombocytopenia and kidney injury caused by a dysregulation of the alternative complement pathway.

Methods

We conducted a multicenter nonregistry study aimed at collecting clinical, laboratory and genetic information of patients with aHUS in Brazil. Demographic data, genetic findings, treatments and outcomes are presented.

Results

Thirty-four patients were included, 62% were female and 67% were Caucasian. Half of the patients had the first manifestation of aHUS before the age of 18 years (pediatric group). Among the 17 patients who had the first manifestation after the age of 18 years (adult group), 6 were kidney transplant patients. Overall, 22 patients (65%) received plasma exchange/plasma infusion (PE/PI) and 31 patients (91%) received eculizumab. Eculizumab was started later in the adult group compared with the pediatric group. Two patients stopped dialysis after PE/PI and 19 patients stopped dialysis after eculizumab despite a late start. A pathogenic/likely pathogenic variant was found in 24.3% of patients. A coexisting condition or trigger was present in 59% of patients (infections, pregnancy, hypertension, autoimmune disease and transplant), especially in the adult group. There was a 30% relapse rate after stopping eculizumab, irrespective of genetic status.

Conclusion

This is the largest case series of aHUS in Brazil involving a wide range of patients for which eculizumab was the main treatment. Although eculizumab was started later than advised in the guidelines, most patients were able to stop dialysis at variable intervals. Discontinuation of eculizumab was associated with a 30% relapse of aHUS.

Pediatric thrombotic thrombocytopenic purpura

Child-onset thrombotic thrombocytopenic purpura (TTP) is a rare entity of thrombotic microangiopathy (TMA). The pathophysiology of the disease is based on a severe functional deficiency of ADAMTS13 (activity <10%), the specific von Willebrand factor (VWF)-cleavage protease. This deficiency may be either acquired (associated anti-ADAMTS13 autoantibodies) or congenital (resulting from biallelic mutations of ADAMTS13 gene). ADAMTS13 deficiency is responsible for the accumulation of high molecular weight multimers of VWF and the formation of platelet thrombi in the microcirculation. Consequently, microangiopathic hemolytic anemia and consumption thrombocytopenia are associated with organ ischemia. The differential diagnosis with other TMAs, autoimmune cytopenias or hematological malignancies may be challenging. The exploration of ADAMTS13 (activity, antibodies, antigen, ADAMTS13 gene) supports the diagnosis of TTP. The first-line treatment of the acute phase of TTP is based on plasmatherapy. In congenital TTP, patients with a chronic disease benefit from a prophylactic plasmatherapy. In autoimmune TTP, steroids and B-cells depleting therapies increasingly are used together with plasma exchange. Long-term follow-up including the monitoring of ADAMTS13 activity is mandatory. A severe decrease in ADAMTS13 activity (<10%) may predict relapses and preemptive B-cell depletion with rituximab can be used to prevent relapses.