Search

Defective complement inhibition can lead to the formation of membrane attack complexes (MAC; C5b‐9) on the plasma membranes of vascular endothelial cells, resulting in injury that drives the progression of thrombotic microangiopathy (TMA), a key pathology in kidney disease.

The incidence of idiopathic nephrotic syndrome (NS) is 1·15–16·9 per 100 000 children, varying by ethnicity and region. The cause remains unknown but the pathogenesis of idiopathic NS is thought to involve immune dysregulation, systemic circulating factors, or inherited structural abnormalities of the podocyte. Genetic risk is more commonly described among children with steroid-resistant disease. The mainstay of therapy is prednisone for the vast majority of patients who are steroid responsive; however, the disease can run a frequently relapsing course, necessitating the need for alternative immunosuppressive agents. Infection and venous thromboembolism are the main complications of NS with also increased risk of acute kidney injury. Prognosis in terms of long-term kidney outcome overall is excellent for steroid-responsive disease, and steroid resistance is an important determinant of future risk of chronic or end-stage kidney disease.

The prevalence of hypertension in children with type 1 diabetes is reported to be between 6% and 16%. This potentially modifiable cardiovascular risk factor may go undiagnosed and undertreated, particularly in children with type 1 diabetes. Recent updated Canadian clinical practice guidelines recommend blood pressure screening every 2 years in children with type 1 diabetes as well as routine use of ambulatory blood pressure monitoring. Risk factors for hypertension in type 1 diabetes include poor glycemic control, overweight and obesity and genetic predisposition for hypertension. In terms of pathophysiology, sustained hyperglycemia, angiotensin I and II and inflammatory cytokines have been implicated. Endothelial and vascular dysfunction, with impaired endothelial-dependent vasodilation and increased carotid artery intima-media thickness, are evident in preclinical and clinical studies of children and not just in adults with type 1 diabetes. Early targeted therapy is critical to the control of hypertension and the development of related morbidity. As with hypertension in adults with type 1 diabetes, lifestyle modifications remain first-line therapy, including diet and glycemic control. Initial antihypertensive therapy should be an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker because of their associated effects of reducing microalbuminuria and improving renovascular outcomes. Pediatric hypertension in type 1 diabetes is an area of evolving study and opinion; identification and appropriate treatment is critical for the prevention of micro- and macrovascular complications in adulthood.

Atypical hemolytic uremic syndrome and thrombotic thrombocytopenic purpura have traditionally been considered separate entities. Defects in the regulation of the complement alternative pathway occur in atypical hemolytic uremic syndrome, and defects in the cleavage of von Willebrand factor (VWF)-multimers arise in thrombotic thrombocytopenic purpura. However, recent studies suggest that both entities are related as defects in the disease-causing pathways overlap or show functional interactions. Here we investigate the possible functional link of VWF-multimers and the complement system on endothelial cells. Blood outgrowth endothelial cells (BOECs) were obtained from 3 healthy individuals and 2 patients with Type 3 von Willebrand disease lacking VWF. Cells were exposed to a standardized complement challenge via the combination of classical and alternative pathway activation and 50% normal human serum resulting in complement fixation to the endothelial surface. Under these conditions we found the expected release of VWF-multimers causing platelet adhesion onto BOECs from healthy individuals. Importantly, in BOECs derived from patients with von Willebrand disease complement C3c deposition and cytotoxicity were more pronounced than on BOECs derived from normal individuals. This is of particular importance as primary glomerular endothelial cells display a heterogeneous expression pattern of VWF with overall reduced VWF abundance. Thus, our results support a mechanistic link between VWF-multimers and the complement system. However, our findings also identify VWF as a new complement regulator on vascular endothelial cells and suggest that VWF has a protective effect on endothelial cells and complement-mediated injury.