Del(18p) syndrome with increased nuchal translucency in prenatal diagnosis

We report a de novo translocation between chromosome 15 and 18 resulting in monosomy 18p in prenatal diagnosis. The patient was referred for amniocentesis due to increased nuchal translucency (INT) (5 mm) at 13.6 weeks of gestation. Karyotype of the fetus revealed 45,XX,der(15;18)(q10;q10) in all metaphases. The targeted fetal ultrasound at 20 weeks of gestation did not show any special physical abnormalities other than 6.4 mm of nuchal fold thickness. Molecular cytogenetic findings using CGH and FISH confirmed the del(18p) with dicentromeres from both chromosome 15 and 18. The present study shows that the INT at first trimester was the only prenatal finding for the fetus with del(18p) syndrome and that molecular cytogenetic methods are useful for detecting chromosomal aberrations precisely. Copyright © 2004 John Wiley & Sons, Ltd.     

Structural chromosomal mosaicism and prenatal diagnosis

True structural chromosomal mosaicism are rare events in prenatal cytogenetics practice and may lead to diagnostic and prognostic problems. Here is described the case of a fetus carrying an abnormal chromosome 15 made of a whole chromosome 2p translocated on its short arm in 10% of the cells, in association with a normal cell line. The fetal karyotype was 46,XX,add(15)(p10).ish t(2;15)(p10;q10)(WCP2+)[3]/46,XX[27]. Pregnancy was terminated and fetus examination revealed a growth retardation associated with a dysmorphism including dolichocephaly, hypertelorism, high forehead, low-set ears with prominent anthelix and a small nose, which were characteristic of partial trisomy 2p. Possible aetiologies for prenatal mosaicism involving a chromosomal structural abnormality are discussed. Copyright © 2004 John Wiley & Sons, Ltd.