CFH and atypical hemolytic-uremic syndrome: The H3 CFH haplotype, which had been previously associated with the risk of atypical HUS [24] and with reduced plasma levels of factor H, was identified only in 2 patients (both are heterozygous) with an allele frequency of 0.11, which is not different from the allele frequency (0.17) that we previously reported in healthy subjects [25].