RESUMO
Down syndrome is the most common autosomal chromosomal abnormality characterized by mental and growth retardation, and by various typical features including prominent epicanthal fold, oblique palpebral fissure, flat nasal bridge, short and broad hand, wide toe interspace, etc. The overall incidence has been shown to be 1:800 deliveries, increasing with advancing maternal age. However, twin cases are extremely rare, and thus far only 500 cases were reported worldwide. We have recently observed 10-day-old male monozygotic twins with Down syndrome, born to a mother of 30 years of age with one normal child. Both have VSD confirmed by 2D-echocardiography, in addition to various typical features. Cytogenetic examination revealed that both have karyotypes of 47, XY, +21. This is the first report in Korea as the authors are aware of.