Pathologic thrombosis is a major cause of mortality. Hemolytic-uremic syndrome (HUS) features episodes of small vessel thrombosis resulting in microangiopathic hemolytic anemia, thrombocytopenia and renal failure1. Atypical HUS (aHUS) can result from genetic or autoimmune factors2 that lead to pathologic complement cascade activation3. By exome sequencing we identify recessive mutations in DGKE (diacylglycerol kinase epsilon) that co-segregate with aHUS in 9 unrelated kindreds, defining a distinctive Mendelian disease. Affected patients present with aHUS before age 1, have persistent hypertension, hematuria and proteinuria (sometimes nephrotic range), and develop chronic kidney disease with age. DGKE is found in endothelium, platelets, and podocytes. Arachidonic acid-containing diacylglycerols (DAG) activate protein kinase C, which promotes thrombosis. DGKE normally inactivates DAG signaling. We infer that loss of DGKE function results in a pro-thrombotic state. These findings identify a new mechanism of pathologic thrombosis and kidney failure and have immediate implications for treatment of aHUS patients.

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We investigated the value of genetic, histopathologic, and early treatment response information in prognosing long-term renal outcome in children with primary steroid-resistant nephrotic syndrome. From the PodoNet Registry, we obtained longitudinal clinical information for 1354 patients (disease onset at >3 months and <20 years of age): 612 had documented responsiveness to intensified immunosuppression (IIS), 1155 had kidney biopsy results, and 212 had an established genetic diagnosis. We assessed risk factors for ESRD using multivariate Cox regression models. Complete and partial remission of proteinuria within 12 months of disease onset occurred in 24.5% and 16.5% of children, respectively, with the highest remission rates achieved with calcineurin inhibitor-based protocols. Ten-year ESRD-free survival rates were 43%, 94%, and 72% in children with IIS resistance, complete remission, and partial remission, respectively; 27% in children with a genetic diagnosis; and 79% and 52% in children with histopathologic findings of minimal change glomerulopathy and FSGS, respectively. Five-year ESRD-free survival rate was 21% for diffuse mesangial sclerosis. IIS responsiveness, presence of a genetic diagnosis, and FSGS or diffuse mesangial sclerosis on initial biopsy as well as age, serum albumin concentration, and CKD stage at onset affected ESRD risk. Our findings suggest that responsiveness to initial IIS and detection of a hereditary podocytopathy are prognostic indicators of favorable and poor long-term outcome, respectively, in children with steroid-resistant nephrotic syndrome. Children with multidrug-resistant sporadic disease show better renal survival than those with genetic disease. Furthermore, histopathologic findings may retain prognostic relevance when a genetic diagnosis is established.

WT1 mutations cause a wide spectrum of renal and extrarenal manifestations. Here we evaluated disease prevalence, phenotype spectrum, and genotype-phenotype correlations of 61 patients with WT1-related steroid-resistant nephrotic syndrome relative to 700 WT1-negative patients, all with steroid-resistant nephrotic syndrome. WT1 patients more frequently presented with chronic kidney disease and hypertension at diagnosis and exhibited more rapid disease progression. Focal segmental glomerulosclerosis was equally prevalent in both cohorts, but diffuse mesangial sclerosis was largely specific for WT1 disease and was present in 34% of cases. Sex reversal and/or urogenital abnormalities (52%), Wilms tumor (38%), and gonadoblastoma (5%) were almost exclusive to WT1 disease. Missense substitutions affecting DNA-binding residues were associated with diffuse mesangial sclerosis (74%), early steroid-resistant nephrotic syndrome onset, and rapid progression to ESRD. Truncating mutations conferred the highest Wilms tumor risk (78%) but typically late-onset steroid-resistant nephrotic syndrome. Intronic (KTS) mutations were most likely to present as isolated steroid-resistant nephrotic syndrome (37%) with a median onset at an age of 4.5 years, focal segmental glomerulosclerosis on biopsy, and slow progression (median ESRD age 13.6 years). Thus, there is a wide range of expressivity, solid genotype-phenotype associations, and a high risk and significance of extrarenal complications in WT1-associated nephropathy. We suggest that all children with steroid-resistant nephrotic syndrome undergo WT1 gene screening.

Childhood renal osteodystrophy (ROD) is the consequence of disturbances of the calcium-regulating hormones vitamin D and parathyroid hormone (PTH) as well as of the somatotroph hormone axis associated with local modulation of bone and growth cartilage function. The resulting growth retardation and the potentially rapid onset of ROD in children are different from ROD in adults. The biochemical changes of ROD as well as its prevention and treatment affect calcium and phosphorus homeostasis and are directly associated with the development of cardiovascular disease in pediatric renal patients. The aims of the clinical and biochemical surveillance of pediatric patients with CRF or on dialysis are prevention of hyperphosphatemia, avoidance of hypercalcemia and keeping the calcium phosphorus product below 5 mmol 2 /l 2 . The PTH levels should be within the normal range in chronic renal failure (CRF) and up to 2-3 times the upper limit of normal levels in dialysed children. Prevention of ROD is expected to result in improved growth and less vascular calcification.