Cosegregation of a missense mutation of RPS19 gene in a family with various clinical phenotypes in monozygotic twins. A single nucleotide substitution (302 G→A) resulting in an amino acid change of a consensus residue (Arg101His) was found in monozygotic twins (II-2 and II-3) from family I11, with only 1 of them presenting with a duplication of the thumb. The same mutation was also found in the healthy father (I-1), who only exhibited a macrocytosis. eADA values are expressed as SD from the mean. NA, not available.