Background Severe hypertension can induce thrombotic microangiopathy (TMA) in the renal vasculature, the occurrence of which has been linked to mechanical stress to the endothelium. Complement defects may be the culprit of disease in patients who present with severe renal disease and often progress to ESRD, despite BP control. Methods We studied a well defined cohort of 17 patients with hypertension-associated TMA to define the prevalence of complement defects by a specific ex vivo serum-based microvascular endothelial cell assay. Results Compared with normal human serum and samples from patients with hypertensive arterionephrosclerosis, 14 of 16 (87.5%) serum samples collected at presentation from 16 patients with hypertension-associated TMA induced abnormal C5b9 formation on microvascular endothelial cells. We detected rare variants in complement genes in eight of 17 (47%) patients. ESRD occurred in 14 of 17 (82%) patients, and recurrent TMA after transplant occurred in seven of 11 (64%) donor kidneys. Eculizumab improved the renal function in three patients and prevented TMA recurrence in an allograft recipient. Conclusions These observations point to complement defects as the key causative factor of ESRD and recurrent TMA after transplant in patients presenting with severe hypertension. Complement defects can be identified by measurements of complement activation on microvascular endothelial cells, which should substantially influence treatment and prognosis.

Hypertensive emergency can cause thrombotic microangiopathy (TMA) in the kidneys with high rates of end-stage renal disease (ESRD) and vice versa. The conundrum of hypertension as the cause of TMA or consequence of TMA on the background of defects in complement regulation remains difficult. Patients with hypertensive emergency and TMA on kidney biopsy were tested for ex vivo C5b9 formation on the endothelium and rare variants in complement genes to identify complement-mediated TMA. We identified factors associated with defects in complement regulation and poor renal outcomes. Massive ex vivo C5b9 formation was found on resting endothelial cells in 18 (69%) out of 26 cases at the presentation, including the 9 patients who carried at least one rare genetic variant. Thirteen (72%, N =18) and 3 (38%, N =8) patients with massive and normal ex vivo complement activation, respectively, progressed to ESRD ( P =0.03). In contrast to BP control, inhibition of C5 activation prevented ESRD to occur in 5 (83%, N =6) patients with massive ex vivo complement activation. TMA-related graft failure occurred in 7 (47%, N =15) donor kidneys and was linked to genetic variants. The assessment of both ex vivo C5b9 formation and screening for rare variants in complement genes may categorize patients with hypertensive emergency and TMA into different groups with potential therapeutic and prognostic implications. We propose an algorithm to recognize patients at the highest risk for defects in complement regulation.

Background: The natural course of idiopathic membranous nephropathy (MN) varies, as it is known through favorable outcomes in most patients. However, one third of patients with idiopathic MN will slowly progress to end-stage renal disease (ESRD). To prevent disease progression, patients at high risk to develop ESRD are treated with immunosuppressive agents. Therefore, a correct selection of patients who need immunosuppressive treatment is important. Methods: Here, we evaluated the prognostic value of anti-phospholipase A2 receptor 1 antibody (anti-PLA2R) levels regarding clinical outcome in a well-defined cohort of 73 PLA2R-related MN patients with long-term follow-up. At baseline, patients were subdivided into patients with either low or high antibody levels based on ELISA testing. Results: Spontaneous remission rates were highest among patients with low anti-PLA2R levels (79%; hazard ratio 2.72 (95% CI 1.22-6.08), p = 0.02) after a median follow-up of 2.9 (95% CI 0.8-5.0, p < 0.001) years, whereas high anti-PLA2R levels were associated with persistent proteinuria (p = 0.04) and/or the need for immunosuppressive therapy (p < 0.001). Renal survival rates were 97% at 5 years, 93% at 10 years, and 89% at 15 years; however, this was not different between the anti-PLA2R groups. ESRD occurred significantly faster in patients with severe proteinuria as compared to patients with either mild (p = 0.02) or moderate proteinuria (p = 0.05). Conclusions: Low anti-PLA2R levels may predict spontaneous remissions in patients with PLA2R-related MN. Therefore, we suggest that quantification of anti-PLA2R is of value to monitor these patients.

Objectives:. Autoantibodies against the M-type phospholipase A2 receptor 1 (anti-PLA2R1) have been demonstrated to be very specific for idiopathic memb