Haplotype analysis on markers flanking MCP gene of family no. 099 and of patient S222 212, both of Sardinian origin, showing that a common allele carrying the mutation is present. The mutation is present in homozygosity in 2 affected siblings (F166 099 and F167 099) in family no. 099 from nonconsanguineous parents, both carrying the mutation in heterozygosity. Of note, the 2 siblings developed HUS very early in life (before 4 years of age) whereas their father (F168 099) developed HUS in adulthood and their mother is still healthy. Three other healthy family members carry the mutation in heterozygosity (marked with ·). Circles indicate females; squares, males; filled symbols, affected individuals; and open symbols, unaffected individuals.