Mutations in membrane cofactor protein (CD46) gene in Indian children with hemolytic uremic syndrome

Background: Mutations in the CD46 gene account for an important proportion of patients with atypical hemolytic uremic syndrome (aHUS) who characteristically show multiple relapses, no response to plasma exchange and low recurrence risk in allograft. We screened for mutations in CD46 in patients with and without circulating anti-factor H (FH) antibodies– associated aHUS. Methods: We estimated CD46 surface expression by flow cytometry and sequenced the CD46 gene in 23 and 56 patients with and without circulating anti-FH antibodies, respectively. Human Splicing Finder and PolyPhen2 were used for in silico prediction of pathogenicity. Results: Two novel and three known (c.286þ2T>G, c.104G>A and c.565T>G) mutations in CD46 were found in nine (11.4%) patients; one patient had a variant of unknown significance and two patients presented during the first year of life. Novel intronic (c.1127þ46C>G) and exonic (c.911C>T) mutations are proposed to activate cryptic splicing sites or alter protein conformation. Markedly reduced CD46 surface expression was found in homozygous states in five patients. Conclusion: Patients with mutations in CD46 present at all ages, including the first year of life. Mutations in intron 2, (c.286þ2T>G) may be a potential hot spot in Indian children. Flow cytometry for CD46 expression is a satisfactory screening tool enabling early diagnosis.