RESUMO
We carried out a protein and genetic investigation of the factor H gene mutations within two families presenting with a diagnostic suspicion of atypical hemolytic uremic syndrome (aHUS). The results within the patients of the first family revealed a factor H-deficiency. Direct sequencing allowed the detection of a 4-nucleotide deletion in the factor H gene. This deletion was found as the homozygote form in the proband and as the heterozygote form in the parents. Protein and functional analyses of the complement system were normal in all members of the second family. However, the molecular investigation for the father showed the presence of an amino acid substitution in the FH gene. Unfortunately, his two affected children died without being investigated for mutations. The functional consequences of these abnormal proteins are still to be demonstrated.