Anti-CFH-associated hemolytic uremic syndrome: do we still need plasma exchange?

BACKGROUND

Between 5 and 50% of atypical hemolytic uremic syndrome (aHUS) cases in children are caused by autoantibodies against complement factor H (CFH). Given the acquired autoimmune nature of the disease, plasma exchange (PE) and various immunosuppressive treatments have been used. More recently, eculizumab has been proposed.

METHODS

In this multicenter, retrospective study, we report outcomes of 12 children with anti-FH antibody-associated HUS treated with eculizumab associated with various immunosuppressive regimens.

RESULTS

Patients were treated with eculizumab for 15.5 [9.5;23.0] months and 3 received PE or IgG adsorption. Three patients received mycophenolate mofetil (MMF) alone, 1 patient received MMF and steroids, 1 patient received MMF and rituximab, 3 patients received MMF/steroids and rituximab, and 4 patients did not receive any immunosuppression. Anti-FH antibody levels significantly decreased but no difference was observed based on the immunosuppressive regimen. Eculizumab was discontinued in 7/10 patients after 11 [7.5;15.5] months and MMF in 6/8 patients after 36 [35;40] months. Anti-FH titers at MMF discontinuation ranged from 257 to 3425 UI/L. None of these patients relapsed and eGFR at last follow-up was above 70 mL/min/1.73 m2 in all patients.

CONCLUSIONS

Eculizumab is effective and safe in inducing and maintaining remission in aHUS secondary to anti-FH antibodies and renders reduction of anti-FH titers less urgent. Anti-FH antibody titers decreased in most patients irrespective of the immunosuppressive treatment chosen, so that a strategy consisting of combining eculizumab with MMF monotherapy seems sufficient at least in non-Indian or less severe forms of anti-FH antibody-associated HUS.

Hot Spot of Complement Factor I Rare Variant p.Ile357Met in Patients With Hemolytic Uremic Syndrome

Atypical hemolytic uremic syndrome (aHUS) is a rare kidney disease due to a dysregulation of the complement alternative pathway. Complement factor I (CFI) negatively regulates the alternative pathway and CFI gene rare variants have been associated to aHUS with a low disease penetrance. We report 10 unrelated cases of HUS associated to a rare CFI variant, p.Ile357Met (c.1071T>G). All patients with isolated p.Ile357Met CFI missense variant were retrospectively identified among patients included between January 2007 and January 2022 in the French HUS Registry. We identified 10 unrelated patients (70% women; median age at HUS diagnosis, 36.5 years) who carry the same rare variant p.Ile357Met in the CFI gene. Seven patients (cases 1-7) presented with aHUS in the native kidney associated with malignant hypertension in 5 patients. None received a C5 inhibitor. Two of these cases occurred in the peripartum period with complete recovery of kidney function, while 5 of these patients reached kidney failure requiring replacement therapy (KFRT). Four patients with KFRT subsequently underwent kidney transplantation. Three later developed C3 glomerulopathy in their kidney graft, but none had aHUS recurrence. Three other patients (cases 8-10) experienced de novo thrombotic microangiopathy after kidney transplantation, precipitated by various triggers. The rare CFI variant p.Ile357Met appears to be a facilitating genetic factor for HUS and for some forms of secondary HUS.

A Critical Care Standpoint in the Diagnosis of Scleroderma Renal Crisis

Typical or atypical presentations of rare diseases may be confounded by co-morbidities in critically-ill patients. It is imperative to diagnose and treat appropriately, despite this difficulty. Scleroderma renal crisis mimics many other conditions, and can be potentially fatal if not caught early enough. Particularly, in critically-ill patients with multiple pathologies, it can be difficult to distinguish scleroderma renal crisis from other diseases, such as thrombotic thrombocytopenic purpura (TTP), hypertensive emergency, posterior reversible encephalopathy syndrome (PRES), or atypical hemolytic uremic syndrome (HUS). Herein, a patient who presented with encephalopathy and seizures was initially treated for thrombotic thrombocytopenic purpura, but was ultimately diagnosed with scleroderma renal crisis. Given her numerous laboratory abnormalities, such as thrombocytopenia, hemolytic anemia, kidney and liver dysfunction, and elevated inflammatory markers, various differentials were considered. During her hospitalization, she suffered a cardiac arrest, seizures, nosocomial infections and worsening kidney disease requiring dialysis, making the final diagnosis of scleroderma renal crisis a diagnosis of exclusion. Subsequently, the management of a patient with multiple co-morbidities and confounding laboratory abnormalities difficult to treat. This article highlights these intricacies and formulates the thought process behind the diagnosis of Scleroderma Renal Crisis.

Mycoplasma pneumoniae Infection Associated with Anti-Factor H Autoantibodies in Atypical Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is a rare disease characterized by hemolytic anemia, thrombocytopenia, and renal impairment mostly triggered by strains of Shiga-like toxin-producing Escherichia coli (STEC-HUS). A rarer form of HUS, defined as atypical HUS (aHUS), is associated with genetic or acquired dysregulation of the alternative pathway of the complement system and presents a poorer prognosis than STEC-HUS. Factor H autoantibodies (anti-FHs) have been reported in aHUS in 5-11% of cases and are strongly associated with the homozygous deletion of CFHR3-CFHR1 genes. In the large majority of patients, anti-FH-associated aHUS is commonly preceded by gastrointestinal or respiratory tract infections. Here, we described the clinical case of a 3-year-old boy who was hospitalized for aHUS preceded by Mycoplasma pneumoniae (MP) infection. He resulted positive for anti-FHs and carried the homozygous deletion of CFHR3-CFHR1. Of relevance, he also showed a variant of unknown significance in the C5 gene. The patient was successfully treated with eculizumab and achieved hematological and renal remission. The anti-FH titer decreased, became negative after 6 months of mycophenolate mofetil (MMF) treatment, and remained negative for 21-month follow-up indicating that immunosuppression was effective and could prevent the reappearance of anti-FHs. We hypothesized that MP, likely through an evasion strategy of immunosurveillance based on binding of pathogen to FH, triggers anti-FH antibody generation and aHUS in a subject genetically predisposed. In conclusion, to the best of our knowledge, here, we reported the first case of anti-FH-mediated aHUS after an MP infection who benefited from eculizumab and immunosuppressive therapy based on MMF. Hence, monitoring of anti-FHs in patients with post-MP infection glomerulonephritis could be recommended, especially in those with low C3 plasma levels.

Pediatric atypical hemolytic-uremic syndrome due to auto-antibodies against factor H: is there an interest to combine eculizumab and mycophenolate mofetil?

BACKGROUND

Atypical hemolytic and uremic syndrome (aHUS), a thrombotic micro-angiopathy (TMA) caused by deregulation in the complement pathway, is sometimes due to the presence of anti-complement factor H (CFH) auto-antibodies. The "standard" treatment for such aHUS combines plasma exchange therapy and immunosuppressive drugs. Eculizumab, a monoclonal antibody that blocks the terminal pathway of the complement cascade, could be an interesting alternative in association with an immunosuppressive treatment for maintenance regimen.

CASE-DIAGNOSIS/TREATMENT

We report on two children, diagnosed with mildly severe aHUS due to anti-CFH antibodies, who were treated with the association eculizumab-mycophenolate mofetil (MMF). Neither side effects nor relapses were observed during the 3 years of follow-up; MMF was even progressively tapered and withdrawn successfully in one patient.

CONCLUSIONS

The association of eculizumab and MMF appears to be an effective and safe option in pediatric cases of aHUS due to anti-CFH antibodies of mild severity.

Typical and Atypical Hemolytic Uremic Syndrome in the Critically Ill

Hemolytic uremic syndrome is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Disseminated intravascular coagulation, thrombotic thrombocytopenic purpura, and hemolytic uremic syndrome have a similar clinical presentation. Diagnostic needs to be prompt to decrease mortality, because identifying the different disorders can help to tailor specific, effective therapies. However, diagnosis is challenging and morbidity and mortality remain high, especially in the critically ill population. Development of clinical prediction scores and rapid diagnostic tests for hemolytic uremic syndrome based on mechanistic knowledge are needed to facilitate early diagnosis and assign timely specific treatments to patients with hemolytic uremic syndrome variants.

Hemolytic uremic syndrome associated with Bordetella pertussis infection in a 2-month-old infant carrying a pathogenic variant in complement factor H

BACKGROUND

Hemolytic uremic syndrome (HUS) has been associated with a number of infectious agents. We report here the case of an infant with severe Bordetella pertussis infection who developed HUS.

CASE DIAGNOSIS/TREATMENT

A 2-month-old preterm male was admitted for severe Bordetella pertussis infection. Symptoms leading to a diagnosis of hemolytic uremic syndrome (HUS) rapidly appeared: hemolytic anemia, thrombocytopenia, and acute kidney injury. He was treated with 25 days of peritoneal dialysis and received complement-targeting therapy with eculizumab (five injections over 2 months), in addition to blood transfusions, antibiotics, and respiratory support. The outcome was favorable. The genetic workup found a complement factor H gene variant which has been associated with atypical HUS. This variant was located in the C3b-binding site and functional tests revealed that it perturbed the regulatory activity of factor H.

CONCLUSION

This case suggests that pertussis is a strong trigger of HUS and that complement investigations are necessary to guide treatment and understand the pathophysiology.

Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is the clinical triad of thrombocytopenia, anemia, and acute kidney injury. Classically associated with enterocolitis from Shiga toxin-producing Escherichia coli, HUS is also associated with Streptococcus pneumoniae infections; genetic dysregulation of the alternative complement pathway or coagulation cascade; and, rarely, a hereditary disorder of cobalamin C metabolism. These share a common final pathway of a prothrombotic and proinflammatory state on the endothelial cell surface, with fibrin and platelet deposition. Much work has been done to distinguish between the different mechanisms of disease, thereby informing the optimal therapeutic interventions for each entity.

Hemolytic uremic syndrome with dual caution in an infant: cobalamin C defect and complement dysregulation successfully treated with eculizumab

BACKGROUND

Hemolytic uremic syndrome (HUS) is a clinical syndrome characterized by hemolytic anemia, thrombocytopenia, and acute kidney injury. Atypical hemolytic uremic syndrome (aHUS) is a devastating disease with significant mortality and high risk of progression to end-stage kidney disease. It is mostly caused by dysregulation of the alternative complement pathway. Cobalamin C (Cbl C) defect is a genetic disorder of cobalamin metabolism and is a rare cause of HUS.

CASE-DIAGNOSIS/TREATMENT

We present a 6-month-old male infant who was admitted to the pediatric intensive care unit (PICU) due to restlessness, severe hypertension, anemia, respiratory distress, and acute kidney injury. Metabolic screening revealed elevated plasma homocysteine levels, low methionine levels, and methylmalonic aciduria, and the patient was diagnosed as having HUS secondary to Cbl C defect. Additionally, complement factor H (CFH) and complement C3 levels were decreased. The infant was treated with betaine, hydroxycobalamin, and folic acid. After treatment, the homocysteine and methylmalonic acid levels were normalized but hemolysis and acute kidney failure persisted. He required continued renal replacement treatment (CRRT) and plasma exchange due to thrombotic microangiopathy (TMA). Therefore, we considered a second mechanism in the pathogenesis as complement dysregulation and gave eculizumab to the patient. After eculizumab treatment, the renal and hematologic indices improved and he was free of dialysis.

CONCLUSIONS

To the best of our knowledge, our patient is the first to have Cbl C defect-HUS accompanied by complement dysregulation, who responded well to eculizumab therapy.

[Atypical hemolytic uremic syndrome in an elderly patient successfully treated with eculizumab]

Herein, we present an elderly onset case of aHUS successfully treated with eculizumab. An 80-year-old woman with severe anemia, thrombocytopenia, and acute renal dysfunction was admitted to our hospital. A laboratory test revealed steep elevation in the LDH level, and the peripheral blood smear showed erythrocyte fragmentations. Accordingly, we diagnosed thrombotic microangiopathy, and treatment with plasma exchange was immediately initiated. In addition, she required hemodialysis because of rapid impairment of the renal function. After excluding Shiga toxin-producing Escherichia coli infection and malignancy and confirming her ADMTS13 activity above 10%, we diagnosed aHUS, according to the Japanese diagnostic criteria for aHUS. Next, we initiated treatment with eculizumab. Her hematological findings improved 23 days after the starting of eculizumab. In addition, her renal function gradually recovered, and hemodialysis was discontinued. The genetic test for several complement regulatory genes tested negative. The onset of aHUS is reported in children or young adults and is rarely reported in elderly. However, our case suggests the importance of precisely diagnosing aHUS and initiating early administration of eculizumab for improving the outcome even in elderly patients.

Case report - atypical hemolytic uremic syndrome triggered by influenza B

BACKGROUND

Influenza A infections have been described to cause secondary hemolytic uremic syndrome and to trigger atypical hemolytic uremic syndrome (aHUS) in individuals with an underlying genetic complement dysregulation. To date, influenza B has not been reported to trigger aHUS.

CASE PRESENTATION

A 6-month-old boy presented with hemolytic uremic syndrome triggered by influenza B infection. Initially the child recovered spontaneously. When he relapsed Eculizumab treatment was initiated, resulting in complete and sustained remission. A pathogenic mutation in membrane cofactor protein (MCP) was detected.

CONCLUSION

Influenza B is a trigger for aHUS and might be underreported as such. Influenza vaccination may protect patients at risk.

Serological and genetic complement alterations in infection-induced and complement-mediated hemolytic uremic syndrome

BACKGROUND

The role of complement in the atypical form of hemolytic uremic syndrome (aHUS) has been investigated extensively in recent years. As the HUS-associated bacteria Shiga-toxin-producing Escherichia coli (STEC) can evade the complement system, we hypothesized that complement dysregulation is also important in infection-induced HUS.

METHODS

Serological profiles (C3, FH, FI, AP activity, C3d, C3bBbP, C3b/c, TCC, αFH) and genetic profiles (CFH, CFI, CD46, CFB, C3) of the alternative complement pathway were prospectively determined in the acute and convalescent phase of disease in children newly diagnosed with STEC-HUS or aHUS. Serological profiles were compared with those of 90 age-matched controls.

RESULTS

Thirty-seven patients were studied (26 STEC-HUS, 11 aHUS). In 39 % of them, including 28 % of STEC-HUS patients, we identified a genetic and/or acquired complement abnormality. In all patient groups, the levels of investigated alternative pathway (AP) activation markers were elevated in the acute phase and normalized in remission. The levels were significantly higher in aHUS than in STEC-HUS patients.

CONCLUSIONS

In both infection-induced HUS and aHUS patients, complement is activated in the acute phase of the disease but not during remission. The C3d/C3 ratio displayed the best discrepancy between acute and convalescent phase and between STEC-HUS and aHUS and might therefore be used as a biomarker in disease diagnosis and monitoring. The presence of aberrations in the alternative complement pathway in STEC-HUS patients was remarkable, as well.

Innovative therapeutic approach: sequential treatment with plasma exchange and eculizumab in a pregnant woman affected by atypical hemolytic-uremic syndrome

The atypical HUS (aHUS) is a rare genetic disease, with poor prognosis, characterized by microangiopathic hemolytic anemia, thrombocytopenia and acute renal failure. This syndrome is often related to mutations in the genes encoding complement regulatory proteins. A 26-year-old woman with homozygous mutation in complement factor H (CFH) developed a relapse of aHUS at 17th week of pregnancy. Despite treatment with plasma exchange (PEX), at the 26th week of gestation eculizumab was started. The sequential treatment with eculizumab after PEX was well tolerated and it has led to clinical remission.