Martin Griebel

Positional cloning uncovers mutations in PLCE1 responsible for a nephrotic syndrome variant that may be reversible

Nephrotic syndrome, a malfunction of the kidney glomerular filter, leads to proteinuria, edema and, in steroid-resistant nephrotic syndrome, end-stage kidney disease. Using positional cloning, we identified mutations in the phospholipase C epsilon gene (PLCE1) as causing early-onset nephrotic syndrome with end-stage kidney disease. Kidney histology of affected individuals showed diffuse mesangial sclerosis (DMS). Using immunofluorescence, we found PLCε1 expression in developing and mature glomerular podocytes and showed that DMS represents an arrest of normal glomerular development. We identified IQ motif–containing GTPase-activating protein 1 as a new interaction partner of PLCε1. Two siblings with a missense mutation in an exon encoding the PLCε1 catalytic domain showed histology characteristic of focal segmental glomerulosclerosis. Notably, two other affected individuals responded to therapy, making this the first report of a molecular cause of nephrotic syndrome that may resolve after therapy. These findings, together with the zebrafish model of human nephrotic syndrome generated by plce1 knockdown, open new inroads into pathophysiology and treatment mechanisms of nephrotic syndrome.

CT and MRI in haemolytic uraemic syndrome with central nervous system involvement: distribution of lesions and prognostic value of imaging findings

Background: Central nervous system (CNS) involvement is a common complication in haemolytic uraemic syndrome (HUS). Various imaging findings have been described, mostly as case reports. Although there are a few retrospective studies on larger patient groups there is no report that focuses on MRI. Objective: To analyse the CT and MRI studies of patients with neurological complications of HUS, to describe the typical imaging findings, and to evaluate their predictive character with regard to follow-up examinations and clinical outcome. Materials and methods: Of 57 patients with clinically proven HUS who were referred to our hospital between 1995 and 2003, 17 had signs of serious CNS involvement and 10 underwent neuroimaging. Nine MRI and seven CT studies were performed in the acute phase and five MRI and two CT studies were done for follow-up. Results: In six patients, pathological imaging findings were seen on CT or MRI performed in the acute phase of the disease whereas CT and MRI scans were completely normal in four patients. All patients with positive imaging findings had pathological changes within the basal ganglia. Additional findings were seen in the thalami (n=2), cerebellum (n=2) and brain stem (n=1). On follow-up imaging performed in five cases, the pathological imaging findings had resolved completely in two and partially in three patients. All patients had a good neurological outcome. Comparing the various MRI findings, a haemorrhagic component within an acute lesion was the most reliable parameter predicting residual pathologic findings on follow-up imaging. Conclusions: Basal ganglia involvement is a typical finding in patients with neurological complications of HUS. Even in patients with severe CNS involvement on acute imaging studies, prognosis was favourable for clinical outcome and resolution of pathological imaging findings.

Serial detection of Epstein–Barr virus DNA in sera and peripheral blood leukocyte samples of pediatric renal allograft recipients with persistent mononucleosis‐like symptoms defines patients at risk to develop post‐transplant lymphoproliferative disease

Abstract:  We tested blood samples of 25 pediatric renal transplant recipients for Epstein–Barr virus (EBV) DNA load by quantitative polymerase chain reaction (PCR). Eleven of these transplant recipients showed clinical persistent mononucleosis‐like symptoms years after transplantation (Tx). A quantitation of EBV DNA by PCR in peripheral blood lymphocyte (PBL) and serum samples revealed variable EBV DNA titers. The majority of EBV PCR results in samples of the 14 asymptomatic transplant recipients was repeatedly below detection limit. In contrast, patients with mononucleosis‐like symptoms showed persistent EBV genome titers over a period of 6 months, ranging from 75 to 18 750 copies/10 000 PBL and from 680 to 335 000 copies/mL serum, respectively. One child suffering from this mononucleosis‐like condition developed an EBV‐associated Burkitt‐like lymphoma 29 months after Tx. Whereas clinical and histological investigations did not indicate a post‐transplant lymphoproliferative disorder (PTLD) until tumor detection, EBV titers in PBL and serum had been high for at least 8 months. We propose that pediatric transplant recipients who show both, recurrent mononucleosis‐like symptoms and a sustained high EBV genome load, are at increased risk for severe EBV‐related post‐transplant complications.

Characterization of the Cytokine Immune Response in Children Who Have Experienced an Episode of Typical Hemolytic-Uremic Syndrome

ABSTRACT The lipopolysaccharide (LPS) of enterohemorrhagic Escherichia coli (EHEC) and Shiga toxin together substantially contribute to the pathophysiology of typical hemolytic-uremic syndrome (HUS). Both factors have been shown to be immune stimulators and could play a key role in the individual innate immune response, characterized by proinflammatory and anti-inflammatory cytokines. By use of a whole blood stimulation model, we therefore compared the LPS- and superantigen-induced cytokine responses in children who had been having recovering from an acute episode of typical HUS for at least 6 months (group 1) with those in controls, who consisted of patients seen in the pediatric neurology outpatient department for routine examination (group 2). Samples were analyzed for cytokine protein levels and the levels of mRNA production. LPS stimulation revealed lower levels of interleukin 10 (IL-10) (P < 0.05) and increased levels of gamma interferon (P < 0.05) and increased ratios of pro- and anti-inflammatory cytokines (P < 0.05 for the IL-1β/IL-10 ratio; P < 0.05 for the tumor necrosis factor alpha/IL-10 ratio) in group 1. In addition superantigen stimulation showed decreased IL-2 levels in group 1 (P < 0.01). Our results suggest an alteration of the cytokine response characterized by high proinflammatory cytokine levels and low anti-inflammatory cytokine levels as well as low levels of IL-2 production in children who have experienced an episode of typical HUS. We hypothesize that this altered immune response is not a residual effect of the infection but a preexisting characteristic of the patient. This could be one reason why individuals infected with EHEC are potentially predisposed to a systemic disease (HUS).

Primary focal segmental glomerulosclerosis – Long-term outcome after pediatric renal transplantation*

Abstract:  Recurrence of the primary disease is a significant issue in pediatric renal transplantation (RTx). According to data reported by the North American Pediatric Renal Transplantation Cooperative Study, patients with focal segmental glomerulosclerosis (FSGS) as primary renal disease have a recurrence rate of 30% after the first RTx. The relative risk of an early graft loss because of recurrent disease is increased to 1.6–3.1 in pediatric patients with FSGS. In a German open multicenter study, which was initiated to investigate mycophenolate mofetil (MMF) after pediatric RTx [Transplantation 2001:71:638, Transplantation 2003:75:454], patients with FSGS were evaluated for recurrence rate, risk factors for recurrence, long‐term graft function, glomerular filtration rate and transplant survival. All patients received immunosuppression with MMF, cyclosporine A and prednisone without induction therapy. Renal function and survival data for FSGS patients were compared with the results of patients with other primary renal diseases within the same study population. Among 86 patients transplanted between 1996 and 1999 eight patients suffered from FSGS as primary disease. Recurrence was diagnosed in two of the eight patients. One out of these two patients lost his graft as a result of recurrence. Risk factors such as time between diagnosis and end stage renal disease (ESRD) and age at onset did not predict recurrence. A three‐year patient survival in the FSGS group was 100%, graft survival 87% vs. 97% in the non‐FSGS group. Acute rejections occurred in three out of eight FSGS patients and in 37 out of 78 among the non‐FSGS group. Long‐term renal function, calculated using mathematical modeling based on glomerular filtration rate (GFR) data during 3 yr after RTx, was similar in FSGS patients – including a patient who had recurrence with a functioning graft – and those without FSGS. In patients with FSGS, recurring disease after RTx remains an important cause of graft loss (one of two patients in this population) even under modern immunosuppressants. Nevertheless, the immunosuppressive regimen used was associated with a similar graft survival rate and long‐term renal function of FSGS patients compared with patients with other primary diseases.

Mycophenolate mofetil introduction stabilizes and subsequent cyclosporine A reduction slightly improves kidney function in pediatric renal transplant patients: a retrospective analysis.

Abstract: Chronic allograft nephropathy (CAN) is the major cause of late graft loss. Among others, chronic calcineurin inhibitor toxicity (CNI) contributes to the development of CAN. Therefore, reduction in CNI dosage may delay the development of CAN, leading to longer graft survival. It was the aim of the present retrospective analysis to investigate the effect of mycophenolate mofetil (MMF) addition with subsequent cyclosporine A (CSA) reduction on renal function in pediatric kidney allograft recipients. Seventeen patients (aged 8.3–17.6 yr) with monotherapy with CSA and progressive loss of renal function at a median of 3.4 yr after kidney transplantation were enrolled. After at least three months of MMF treatment, CSA dosage was stepwise reduced to trough levels of 100, 80, and 60 ng/mL. In all patients, introduction of MMF prevented a further decrease of glomerular filtration rate (GFR). The mean GFR 12 months before study enrollment was 96.1±24.5 and 71.0±21.0 mL/min/1.73 m2 at start of MMF. After introduction of MMF and unchanged CSA dosage GFR was stabilized to 71.1±23.8 mL/min/1.73 m2. After CSA reduction to trough levels of 60 ng/mL, GFR was slightly ameliorated up to 76.3±24.1 mL/min/1.73 m2. Within the follow‐up period, one borderline rejection occurred in a patient in whom the CSA trough level was 60 ng/mL since seven months. In pediatric kidney allograft recipients with progressive loss of renal function reduction of CSA after introduction of MMF may stabilize and even slightly ameliorate renal function.