Elena Román

An update for atypical haemolytic uraemic syndrome: diagnosis and treatment: A consensus document

Haemolytic uraemic syndrome (HUS) is a clinical entity defined as the triad of nonimmune haemolytic anaemia, thrombocytopenia, and acute renal failure, in which the underlying lesions are mediated by systemic thrombotic microangiopathy (TMA). Atypical HUS (aHUS) is a sub-type of HUS in which the TMA phenomena are the consequence of decreased regulation of the alternative complement pathway on cell surfaces due to a genetic cause. aHUS is an extremely rare disease that, despite the administration of standard treatment with plasma therapy, often progresses to terminal chronic renal failure with a high associated rate of mortality. In recent years, research has established the key role that the complement system plays in the induction of endothelial damage in patients with aHUS, through the characterisation of multiple mutations and polymorphisms in the genes that code for certain complement factors. Eculizumab is a monoclonal antibody that inhibits the terminal fraction of the complement protein, blocking the formation of a cell membrane attack complex. In prospective studies in patients with aHUS, administering eculizumab produces a rapid and sustained interruption in the TMA process, with significant improvements in long-term renal function and an important decrease in the need for dialysis or plasma therapy. In this document, we review and bring up to date the important aspects of this disease, with special emphasis on how recent advancements in diagnostic and therapeutic processes can modify the treatment of patients with aHUS.

Effectiveness of mycophenolate mofetil in C3 glomerulonephritis

C3 glomerulonephritis is a clinicopathologic entity defined by the presence of isolated or dominant deposits of C3 on immunofluorescence. To explore the effect of immunosuppression on C3 glomerulonephritis, we studied a series of 60 patients in whom a complete registry of treatments was available over a median follow-up of 47 months. Twenty patients had not received immunosuppressive treatments. In the remaining 40 patients, 22 had been treated with corticosteroids plus mycophenolate mofetil while 18 were treated with other immunosuppressive regimens (corticosteroids alone or corticosteroids plus cyclophosphamide). The number of patients developing end-stage renal disease was significantly lower among treated compared with untreated patients (3 vs. 7 patients, respectively). No patient in the corticosteroids plus mycophenolate mofetil group doubled serum creatinine nor developed end-stage renal disease, as compared with 7 (significant) and 3 (not significant), respectively, in patients treated with other immunosuppressive regimens. Renal survival (100, 80, and 72% at 5 years) and the number of patients achieving clinical remission (86, 50, and 25%) were significantly higher in patients treated with corticosteroids plus mycophenolate mofetil as compared with patients treated with other immunosuppressive regimens and untreated patients, respectively. Thus, immunosuppressive treatments, particularly corticosteroids plus mycophenolate mofetil, can be beneficial in C3 glomerulonephritis.

Elevated factor H–related protein 1 and factor H pathogenic variants decrease complement regulation in IgA nephropathy

IgA nephropathy (IgAN), a frequent cause of chronic kidney disease worldwide, is characterized by mesangial deposition of galactose-deficient IgA1-containing immune complexes. Complement involvement in IgAN pathogenesis is suggested by the glomerular deposition of complement components and the strong protection from IgAN development conferred by the deletion of the CFHR3 and CFHR1 genes (ΔCFHR3-CFHR1). Here we searched for correlations between clinical progression and levels of factor H (FH) and FH-related protein 1 (FHR-1) using well-characterized patient cohorts consisting of 112 patients with IgAN, 46 with non-complement-related autosomal dominant polycystic kidney disease (ADPKD), and 76 control individuals. Patients with either IgAN or ADPKD presented normal FH but abnormally elevated FHR-1 levels and FHR-1/FH ratios compared to control individuals. Highest FHR-1 levels and FHR-1/FH ratios are found in patients with IgAN with disease progression and in patients with ADPKD who have reached chronic kidney disease, suggesting that renal function impairment elevates the FHR-1/FH ratio, which may increase FHR-1/FH competition for activated C3 fragments. Interestingly, ΔCFHR3-CFHR1 homozygotes are protected from IgAN, but not from ADPKD, and we found five IgAN patients with low FH carrying CFH or CFI pathogenic variants. These data support a decreased FH activity in IgAN due to increased FHR-1/FH competition or pathogenic CFH variants. They also suggest that alternative pathway complement activation in patients with IgAN, initially triggered by galactose-deficient IgA1-containing immune complexes, may exacerbate in a vicious circle as renal function deterioration increase FHR-1 levels. Thus, a role of FHR-1 in IgAN pathogenesis is to compete with complement regulation by FH.

Eculizumab in secondary atypical haemolytic uraemic syndrome

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.

Podocytes are new cellular targets of haemoglobin-mediated renal damage: Haemoglobin induces podocyte injury

Recurrent and massive intravascular haemolysis induces proteinuria, glomerulosclerosis, and progressive impairment of renal function, suggesting podocyte injury. However, the effects of haemoglobin (Hb) on podocytes remain unexplored. Our results show that cultured human podocytes or podocytes isolated from murine glomeruli bound and endocytosed Hb through the megalin–cubilin receptor system, thus resulting in increased intracellular Hb catabolism, oxidative stress, activation of the intrinsic apoptosis pathway, and altered podocyte morphology, with decreased expression of the slit diaphragm proteins nephrin and synaptopodin. Hb uptake activated nuclear factor erythroid‐2‐related factor 2 (Nrf2) and induced expression of the Nrf2‐related antioxidant proteins haem oxygenase‐1 (HO‐1) and ferritin. Nrf2 activation and Hb staining was observed in podocytes of mice with intravascular haemolysis. These mice developed proteinuria and showed podocyte injury, characterized by foot process effacement, decreased synaptopodin and nephrin expression, and podocyte apoptosis. These pathological effects were enhanced in Nrf2‐deficient mice, whereas Nrf2 activation with sulphoraphane protected podocytes against Hb toxicity both in vivo and in vitro. Supporting the translational significance of our findings, we observed podocyte damage and podocytes stained for Hb, HO‐1, ferritin and phosphorylated Nrf2 in renal sections and urinary sediments of patients with massive intravascular haemolysis, such as atypical haemolytic uraemic syndrome and paroxysmal nocturnal haemoglobinuria. In conclusion, podocytes take up Hb both in vitro and during intravascular haemolysis, promoting oxidative stress, podocyte dysfunction, and apoptosis. Nrf2 may be a potential therapeutic target to prevent loss of renal function in patients with intravascular haemolysis. Copyright

Estudio radiológico del síndrome de hipertensión venosa renal izquierda en la edad pediátrica

Objetivos Valorar la aportacion al diagnostico y actitud terapeutica de los metodos de imagen utilizados en nuestros casos con sindrome de hipertension venosa renal izquierda (SHVRI). Material y metodos Se revisaron las exploraciones —ecografia modo B, Doppler-color, tomografia computarizada (TC) helicoidal y venografia renal— de nueve pacientes con SHVRI. Se observo la vena renal izquierda (VRI), su situacion anatomica, los posibles trayectos anomalos, el paso en la pinza aortomesenterica, su diametro y la velocidad de flujo en diferentes porciones. Se midio la distancia entre aorta y arteria mesenterica y su angulo en el paso de la VRI. Mediante venografia renal selectiva se cuantifico el gradiente de presion entre VRI y vena cava inferior. Se visualizo la circulacion colateral varicosa compensadora. Resultados Tres pacientes muestran trayectos anomalos de la VRI, dos en posicion retroaortica y uno con vena renal accesoria varicosa por drenaje anomalo, y seis con compresion de VRI en la pinza aortomesenterica. La relacion velocidad de flujo porcion aortomesenterica/hiliar de VRI fue de 3,35 (1,5-5,4); el diametro en hilio renal de 7,18 mm (5-9); la relacion diametros entre ambas porciones de 2,84 (2,5-3,6); la distancia aortomesenterica de 3 mm (2,1-4,3), y el angulo aortomesenterico de 23° (15-26). Dos pacientes presentaron gradiente de presion VRI respecto a vena cava Conclusiones Las anomalias anatomicas de la VRI observadas en TC helicoidal y la hipertension venosa medida por diferencia de gradiente entre VRI y vena cava con circulacion colateral varicosa, son demostrativas del sindrome; sin embargo, la velocidad de flujo, el diametro de la VRI y las medidas anatomicas de la pinza aortomesenterica no fueron concluyentes.