Pregnancy-associated atypical hemolytic uremic syndrome (aHUS) refers to the thrombotic microangiopathy resulting from uncontrolled complement activation during pregnancy or the postpartum period. Pregnancy-associated aHUS is a devastating disease for which there is a limited clinical understanding and treatment experience. Here we report a retrospective study to analyze the clinical and prognostic data of 22 cases of pregnancy-associated aHUS from the Spanish aHUS Registry under different treatments. Sixteen patients presented during the first pregnancy and as many as nine patients required hemodialysis at diagnosis. Identification of inherited complement abnormalities explained nine of the 22 cases, with CFH mutations and CFH to CFHR1 gene conversion events being the most prevalent genetic alterations associated with this disorder (66%). In thirteen of the cases, pregnancy complications were sufficient to trigger a thrombotic microangiopathy in the absence of genetic or acquired complement alterations. The postpartum period was the time with highest risk to develop the disease and the group shows an association of cesarean section with pregnancy-associated aHUS. Seventeen patients underwent plasma treatments with a positive renal response in only three cases. In contrast, ten patients received eculizumab with an excellent renal response in all, independent of carrying or not inherited complement abnormalities. Although the cohort is relatively small, the data suggest that pregnancy-associated aHUS is not different from other types of aHUS and suggest the efficacy of eculizumab treatment over plasma therapies. This study may be useful to improve prognosis in this group of aHUS patients.

Background. Complement dysregulation occurs in thrombotic microangiopathies (TMAs) other than primary atypical haemolytic uraemic syndrome (aHUS). A few of these patients have been reported previously to be successfully treated with eculizumab. Methods. We identified 29 patients with so-called secondary aHUS who had received eculizumab at 11 Spanish nephrology centres. Primary outcome was TMA resolution, defined by a normalization of platelet count (>150 × 109/L) and haemoglobin, disappearance of all the markers of microangiopathic haemolytic anaemia (MAHA), and improvement of renal function, with a ≥25% reduction of serum creatinine from the onset of eculizumab administration. Results. Twenty-nine patients with secondary aHUS (15 drug-induced, 8 associated with systemic diseases, 2 with postpartum, 2 with cancer-related, 1 associated with acute humoral rejection and 1 with intestinal lymphangiectasia) were included in this study. The reason to initiate eculizumab treatment was worsening of renal function and persistence of TMA despite treatment of the TMA cause and plasmapheresis. All patients showed severe MAHA and renal function impairment (14 requiring dialysis) prior to eculizumab treatment and 11 presented severe extrarenal manifestations. A rapid resolution of the TMA was observed in 20 patients (68%), 15 of them showing a ≥50% serum creatinine reduction at the last follow-up. Comprehensive genetic and molecular studies in 22 patients identified complement pathogenic variants in only 2 patients. With these two exceptions, eculizumab was discontinued, after a median of 8 weeks of treatment, without the occurrence of aHUS relapses. Conclusion. Short treatment with eculizumab can result in a rapid improvement of patients with secondary aHUS in whom TMA has persisted and renal function worsened despite treatment of the TMA-inducing condition.

The STARMEN trial indicates that alternating treatment with corticosteroids and cyclophosphamide is superior to sequential treatment with tacrolimus and rituximab in primary membranous nephropathy.

Background and objectivesAtypical hemolytic uremic syndrome is a form of thrombotic microangiopathy caused by dysregulation of the alternative complement pathway. There is evidence showing complement activation in other thrombotic microangiopathies. The aim of this study was to evaluate complement activation in different thrombotic microangiopathies and to monitor treatment response.Design, setting, participants, & measurementsComplement activation was assessed by exposing endothelial cells to sera or activated-patient plasma—citrated plasma mixed with a control sera pool (1:1)—to analyze C5b-9 deposits by immunofluorescence. Patients with atypical hemolytic uremic syndrome (n=34) at different stages of the disease, HELLP syndrome (a pregnancy complication characterized by hemolysis, elevated liver enzymes, and low platelet count) or severe preeclampsia (n=10), and malignant hypertension (n=5) were included.ResultsAcute phase atypical hemolytic uremic syndrome–activated plasma induced an increased C5b-9 deposition on endothelial cells. Standard and lower doses of eculizumab inhibited C5b-9 deposition in all patients with atypical hemolytic uremic syndrome, except in two who showed partial remission and clinical relapse. Significant fibrin formation was observed together with C5b-9 deposition. Results obtained using activated-plasma samples were more marked and reproducible than those obtained with sera. C5b-9 deposition was also increased with samples from patients with HELLP (all cases) and preeclampsia (90%) at disease onset. This increase was sustained in those with HELLP after 40 days, and levels normalized in patients with both HELLP and preeclampsia after 6–9 months. Complement activation in those with malignant hypertension was at control levels.ConclusionsThe proposed methodology identifies complement overactivation in patients with atypical hemolytic uremic syndrome at acute phase and in other diseases such as HELLP syndrome and preeclampsia. Moreover, it is sensitive enough to individually assess the efficiency of the C5 inhibition treatment.

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Atypical hemolytic uremic syndrome (aHUS), a rare form of thrombotic microangiopathy caused by complement pathogenic variants, mainly affects the kidney microvasculature. A retrospective genetic analysis in our aHUS cohort (=513) using multiple ligation probe amplification uncovered nine unrelated patients carrying a genetic abnormality in the complement factor H related 1 gene () that originates by recurrent gene conversion events between the and genes. The novel mutants encode an FHR-1 protein with two amino acid substitutions, L290S and A296V, converting the FHR-1 C terminus into that of factor H (FH). Next-generation massive-parallel DNA sequencing (NGS) analysis did not detect these genetic abnormalities. In addition to the mutant, six patients carried the previously uncharacterized variant. In functional analyses, the mutant FHR-1 protein strongly competed the binding of FH to cell surfaces, impairing complement regulation, whereas the polymorphism lacked functional consequences. Carriers of the mutation presented with severe aHUS during adulthood; 57% of affected women in this cohort presented during the postpartum period. Analyses in patients and unaffected carriers showed that FH plasma levels determined by the nonmutated chromosome modulate disease penetrance. Crucially, in the activated endothelial (HMEC-1) cell assay, reduced FH plasma levels produced by the nonmutated chromosome correlated inversely with impairment of complement regulation, measured as C5b-9 deposition. Our data advance understanding of the genetic complexities underlying aHUS, illustrate the importance of performing functional analysis, and support the use of complementary assays to disclose genetic abnormalities not revealed by current NGS analysis.

Background: Atypical hemolytic uremic syndrome (aHUS) is a rare disease associated with congenital or acquired genetic abnormalities that result in uncontrolled complement activation, leading to thrombotic microangiopathy and kidney failure. Until recently, the only treatment was plasma exchange or plasma infusion (PE/PI), but 60% of patients died or had permanent kidney damage despite treatment. Eculizumab, a complement inhibitor, has shown promising results in aHUS. However, data are mainly extracted from case reports or studies of heterogeneous cohorts, and no direct comparison with PE/PI is available. Methods: An observational retrospective study of adult, dialysis-dependent aHUS patients with acute kidney injury (AKI) who were treated with either PE/PI alone or with second-line eculizumab in our center. We compared the effect of PE/PI and eculizumab on kidney function, hypertension, proteinuria, hematologic values, relapse, and death. Results: Thirty-one patients were included (females, 18; sporadic aHUS, 29; mean age, 46 ± 20 years). Twenty-six patients were treated with PE/PI alone, and 5 were deemed to be plasma-resistant and received eculizumab after stopping PE/PI. Among patients receiving eculizumab, 80% attained complete recovery of kidney function, 100% stopped dialysis, 20% had decreased proteinuria, and no patient relapsed (vs. 38.5, 50, 15.4, and 11.5%, respectively, of patients receiving only PE/PI). At 1-year of follow-up, no deaths had occurred in either group. Conclusion: Eculizumab shows greater efficacy than PE/PI alone for the treatment of adult aHUS patients with AKI. Prospective studies and meta-analyses are warranted to confirm our findings and set guidelines for treatment, monitoring, and maintenance.

Background Thrombotic microangiopathy (TMA) is a complication of malignant hypertension (mHTN) attributed to the high levels of blood pressure (BP). However, no studies have investigated in patients with mHTN of different etiologies whether the presence of TMA is associated with specific causes of mHTN. Methods We investigate the presence of TMA (microangiopathic hemolytic anemia and thrombocytopenia) in a large and well characterized cohort of 199 patients with mHTN of different etiologies (primary HTN 44%, glomerular diseases 16.6%, primary atypical hemolytic uremic syndrome (aHUS) 13.1%, renovascular HTN 9.5%, drug-related HTN 7%, systemic diseases 5.5%, endocrine diseases 4.5%). Outcomes of the study were kidney recovery and kidney failure. Results Patients with TMA (40 cases, 20.1%) were younger, had a lower proportion of males, lower BP levels and worse kidney function at presentation. Their underlying diseases were primary aHUS (60%), drug-related mHTN (15%), glomerular diseases (all of them IgA nephropathy) (10%), systemic diseases (10%) and primary HTN (5%). The presence of TMA was 92.3% in primary aHUS, 42.9% in drug-related HTN, 36.4% in systemic diseases, 12.1% in glomerular diseases and 2.3% in primary HTN. No patient with renovascular HTN or mHTN caused by endocrine diseases developed TMA, despite BP levels as severe as patients with TMA. A higher proportion of TMA patients developed kidney failure as compared to patients without TMA (56.4% versus 38.9%, respectively). Conclusions The presence of TMA in patients with mHTN should guide the diagnosis towards primary aHUS, drug-related mHTN, some systemic diseases and IgA nephropathy, while it is exceptional in other causes of mHTN.