Sidharth Kumar Sethi

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy that associates, in 70% of cases, with genetic or acquired disorders leading to dysregulation of the alternative pathway of complement. Autoantibody directed against Factor H causes at least 6% to 10% of aHUS cases, but only a few clinical reports are available. Here, we describe the clinical, biologic, genetic features, treatment, and outcome of 45 patients who presented with aHUS associated with anti-FH autoantibody. We found that this form of aHUS primarily affects children between 9 and 13 years old but it also affects adults. It presents with a high frequency of gastrointestinal symptoms and with extrarenal complications and has a relapsing course. Activation of the alternative pathway of complement at the onset of disease portends a poor prognosis. Early specific treatment may lead to favorable outcomes. These data should improve the recognition and diagnosis of this form of aHUS and help identify patients at high risk of a poor outcome.

JUSTIFICATION: In 2001, the Indian Pediatric Nephrology Group formulated guidelines for management of patients with steroid sensitive nephrotic syndrome. In view of emerging scientific evidence, it was felt necessary to review the existing recommendations. PROCESS: Following a preliminary meeting in March 2007, a draft statement was prepared and circulated among pediatric nephrologists in the country to arrive at a consensus on the evaluation and management of these patients. OBJECTIVES: To revise and formulate recommendations for management of steroid sensitive nephrotic syndrome. RECOMMENDATIONS: The need for adequate cortico-steroid therapy at the initial episode is emphasized. Guidelines regarding the initial evaluation, indications for renal biopsy and referral to a pediatric nephrologist are updated. It is proposed that patients with frequently relapsing nephrotic syndrome should, at the first instance, be treated with long-term, alternate-day prednisolone. The indications for use of alternative immunosuppressive agents, including levamisole, cyclophosphamide, mycophenolate mofetil and cyclosporin are outlined. The principles of dietary therapy, management of edema, and prevention and management of complications related to nephrotic syndrome are described. These guidelines, formulated on basis of current best practice, are aimed to familiarize physicians regarding management of children with steroid sensitive nephrotic syndrome.

Complement is a major innate immune surveillance system. One of its most important regulators is the plasma protein factor H (FH). FH inactivation by mutations or by autoantibodies is associated with a thrombotic microangiopathy disease, atypical hemolytic uremic syndrome. In this study, we report the characterization of blood samples from 19 anti-FH Ab-positive atypical hemolytic uremic syndrome patients collected at the acute phase of the disease. Analyses of the functional consequences and epitope mapping, using both fluid phase and solid phase approaches, were performed. The anti-FH Abs perturbed FH-mediated cell protection (100%), inhibited FH interaction with C3 (46%), and caused C3 consumption (47%). The Abs were directed against multiple FH epitopes located at the N and C termini. In all tested patients, high titers of FH-containing circulating immune complexes were detected. The circulating immune complex titers correlated with the disease stage better than did the Ab titers. Our results show that anti-FH autoantibodies induce neutralization of FH at acute phase of the disease, leading to an overall impairment of several functions of FH, extending the role of autoantibodies beyond the impairment of the direct cell surface protection.