High resolution chromosome analysis and in situ hybridization on amniotic fluid for diagnosis of a cryptic translocation.

We report a cryptic translocation ascertained in a family after the birth of a mentally retarded proband. High resolution chromosome examination revealed that the father had a subtle translocation between chromosome 5 and chromosome 13, 46, XY, t(5;13) (q35.2;q34). Two specific, non-routine techniques were associated for prenatal diagnosis: high resolution cytogenetic studies on the amniotic fluid and fluorescent in situ hybridization with YACs as specific telomeric probes. The fetus had the same cryptic translocation as his father.