Non-mosaic Tetrasomy Yp by Complex Isodicentric Rearrangement of the Y Chromosome: Prenatal Diagnosis with Cordocentesis in a Fetus with Abnormal Obstetric Ultrasound

Tetrasomy Y is a very rare event, especially when it is present in a complete form. It is determined by complex rearrangement of the Y chromosome. Clinical features include psychomotor delay, skeletal abnormalities and facial dysmorphism. We report on a case of prenatal diagnosis of non-mosaic tetrasomy Yp, performed by karyotype and fluorescence in situ hybridization (FISH) on fetal blood. These analyses showed the presence of two isodicentric Y, with two copies of SRY and one copy of DXZ1 (XCEN) in each one. Karyotype was characterized as 47; X, Isodicentric (Y) (pter?q12::q12?pter) x2 (SRYx4). Cytogenetic studies were performed after detection of abnormal prenatal ultrasound, showing severe intrauterine growth restriction (symmetric IUGR), hydropic placenta, mild cerebellar hypoplasia, microretrognathia, hyperechogenic bowel with slight distension, dilation of recto-sigmoid tract, ambiguous genitalia, clinodactyly of the right fifth finger, suspected polydactyly. It was not possible to make a clear genotypephenotype correlation because a pregnancy interruption was performed.