Despite numerous studies, the clinical heterogeneity of Down syndrome has no explanation. We have attempted to investigate the role of genomic imprinting in the phenotype of liveborn Down syndrome patients. Hundred fifty eight patients were investigated for parental origin of the extra chromosome 21 with standard cytogenetic analyses and with DNA plymorphic markers. The extra chromosome 21 was of paternal origin in 8 cases and of maternal origin in 150 cases.
The phenotype of Down svndrome patients in whom the nondisjunction was of maternal origin, was not different from the phenotype of Down syndrome patients in whom the nondisjunction was of paternal origin.
We conclude that imprinting may probably not play a role in the heterogeneity of Down syndrome phenotype.
