1/5. Pallister-Killian syndrome: difficulties of prenatal diagnosis.The first prenatal diagnosis of Pallister-Killian syndrome (PKS) was reported by Gilgenkrantz et al. in1985. Since this report, about 60 prenatal cases have been reported but both sonographic and cytogenetic diagnoses remain difficult. Although ultrasound anomalies such as congenital diaphragmatic hernia, polyhydramnios and rhizomelic micromelia in association with fetal overgrowth are very suggestive of the syndrome, they are inconstant and they may even be absent. The mosaic distribution of the supernumerary isochromosome 12p greatly increases these difficulties. No prenatal cytogenetic technique is sensitive enough to ensure prenatal diagnosis and false-negative results have been described on fetal blood, chorionic villi and amniocentesis. We report here two prenatal cases of PKS which illustrate the great variability of the fetal phenotype. In reviewing the 63 reported cases, we attempt to determine ultrasound indicators of the syndrome and to define a cytogenetic strategy. In cases where ultrasound indicators are present, our proposal is first to perform chorionic villus or placental sampling and then amniocentesis when the first cytogenetic result is normal. fetal blood sampling is the least indicated method because of the low frequency of the isochromosome in lymphocytes. In this cytogenetic strategy, fluorescent in situ hybridization (FISH) and especially interphase FISH on non-cultured cells increases the probability or identifying the isochromosome. A misdiagnosis remains possible when ultrasound is not contributory; the identification of new discriminating ultrasound indicators would be very helpful in this context.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
2/5. prenatal diagnosis of Pallister-Killian syndrome: resolution of cytogenetic ambiguity by use of fluorescent in situ hybridization.We report a case of Pallister-Killian syndrome initially diagnosed prenatally as tetrasomy 21. A 33-year-old primiparous woman was noted at 24 weeks' gestation to have moderate polyhydramnios. ultrasonography showed diminished fetal stomach filling, hydronephrosis, and prominence of the cisterna magna. cytogenetic analysis of cultured amniocytes was initially interpreted as mosaic tetrasomy 21: 46,XX/47,XX, i(21q). The patient was then referred to our centre for genetic counselling. At 34 weeks' gestation, a dysmorphic infant was delivered and died within 30 min. Physical features were consistent with the Pallister-Killian syndrome. Renal, gastrointestinal, and central nervous system anomalies were found at post-mortem examination. Analysis of peripheral lymphocytes revealed 5 per cent of cells with a marker chromosome, while 92 per cent of cultured fibroblasts had this same marker. Fluorescent in situ hybridization (FISH) using an alpha-satellite probe for chromosomes 13 and 21 failed to hybridize to the marker, while a chromosome 12 centromeric probe unequivocally identified it as an i(12p). Use of FISH can provide rapid, specific prenatal diagnosis of ambiguous marker chromosomes and improve prenatal counselling.- - - - - - - - - - ranking = 5keywords = hybridization (Clic here for more details about this article) |
3/5. Dandy-Walker malformation in a fetus with pentasomy X (49,XXXXX) prenatally diagnosed by fluorescence in situ hybridization technique.We present the case of a pentasomy X (49,XXXXX) prenatally diagnosed. The fluorescent in situ hybridization technique assisted in making the diagnosis. The problems identified in this fetus include a Dandy-Walker malformation, hydrocephaly, ventricular septal defect, hypertelorism and polyhydramnios.- - - - - - - - - - ranking = 5keywords = hybridization (Clic here for more details about this article) |
4/5. Molecular characterization of a complex translocation in a newborn infant.A newborn infant was referred because of low-set ears, mild downward slant of the palpebral fissures, micrognathia with high-arched palate, a flat midface, small mouth, and thin upper lip with cupid bow configuration. To some extent her cry resembled that associated with cri du chat syndrome. Cytogenetic findings with G- and Q-banding alone failed to characterize precisely the complex translocations. By the chromosome in situ suppression (CISS) hybridization technique using whole chromosome specific probes, a complex 4 breakpoint rearrangement involving both arms of a single chromosome 1 with the long arms of chromosomes 5 and 11 was disclosed, i.e., 46,XX, der(1),t(1;5) t(1;11) (5qter-->5q31::1p31.3-->1q44::11q23-->11 qter;5pter-->5q31::1p31.3-->1pter;11pter-- >11q 23::1q44-->1qter). Gene deregulation and position effect may explain the multiple anomalies in individuals with apparently balanced translocations. The molecular characterization of such cytogenetically balanced translocations may shed some light towards unveiling the clinical consequences associated with aberrations which are presumably balanced.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
5/5. polyhydramnios as a prenatal symptom of the digeorge/velo-cardio-facial syndrome.prenatal diagnosis of the DiGeorge/velo-cardio-facial syndrome has become possible since it was recognized that this syndrome is caused by a submicroscopic deletion in chromosome 22q11. In a sporadic patient presenting a conotruncal heart defect and polyhydramnios, the del 22q11 was made prenatally by fluorescence in situ hybridization (FISH) after amniocentesis. Seven additional patients with a del 22q11 were identified, who presented during pregnancy with polyhydramnios. In one of them, unilateral hydronephrosis was present. These findings further add to a growing list of clinical presentations of a del 22q11 and suggest that in patients with polyhydramnios and a conotruncal heart defect or uropathy, fetal karyotyping should be complemented by FISH for a del 22q11.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |