Twins, Probably Monozygotic: One Mongoloid with 48 Chromosomes, the Other Normal

Abstract

A five-year-old mongoloid female twin was found to have the aneuploid number of 48 chromosomes. The karyotypic analysis revealed the presence of trisomy G and an additional abnormal chromosome in the smallest length range. Appropriate measurements of the chromosomes, studies of the association and satellites as well as DNA synthesis have provided certain information about the abnormal chromosome; however, its precise derivation could not be established at this time. The interest in this patient is further enhanced by the finding that she is one of twins, probably monozygotic; her twin sister is normal in all respects. Both twins have identical blood groups, Gm types and haptoglobins. Analysis of the palm and sole prints of the twins is also compatible with their monozygosity. The possible mechanism leading to the chromosomal and clinical abnormality encountered is discussed.