P-10

Prenatal diagnosis: a case of partial trisomy 6Q

Rosário Pinto Leite^I; Pedro Botelho^I; Marta Souto^I; Rosete Nogueira^II,III; António Carvalho^IV; Osvaldo Moutinho^IV,V; Márcia Martins^V

^ILaboratório de Citogenética, Serviço de Genética, Centro Hospitalar Trás-os-Montes e Alto Douro, Vila Real, Portugal
^IIPathology Laboratory CGC Genetics /Centro Genética Clinica, Porto, Portugal
^IIILife and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal; ]]> ^IVServiço de Ginecologia/Obstetrícia, Centro Hospitalar Trás-os-Montes e Alto Douro, Vila Real, Portugal;
^VServiço de Genética, Centro Hospitalar Trás-os-Montes e Alto Douro, Vila Real, Portugal

mlleite@chtmad.min-saude.pt

Partial distal trisomy 6q is a rare event and is characterized by a distinct phenotype which includes microcephaly, acrocephaly, joint contractures and profound psychomotor retardation. The authors present a case of a 30-year-old pregnant woman referred to prenatal diagnosis due to ultrasound anomalies. It was the first pregnancy of a nonconsanguineous couple with no familial or personal story of anomalies. Parents karyotype was performed. Cytogenetic analysis revealed a chromosome 15 with an increase p arm similar to a variation  in  length  of  heterochromatic  stalks on the short arm. Both parents presented a chromosome 15 with satellites but different from the one detect at the amniocytes. Subtelomeric FISH analysis revealed a trisomy of 6q27-qter present at p arm of chromosome 15 it was a de novo rearrangement.The parents decided to terminate the pregnancy and foetal autopsy was required. Several polymorphic variants were described in human chromosome 15 including increased amounts of short arm hetrochromatin (ph+), interpreted as a normal polymorphism.In the majority of cases partial trisomy 6q results from a balanced chromosomal rearrangement in one of the parents, usually of maternal origin. There have also been rare cases in which partial trisomy 6q has appeared from spontaneous (de novo) errors very early in embryonic development. The authors compared the cytogenetic and the foetal autopsy findings with those described in the literature. Every new case of a rare chromosomal alteration should be reported in order to establish a genotype/ phenotype correlation, improving risk evaluation and genetic counseling.