Prevalence of aneuploidies in products of spontaneous abortion: interest of FISH and MLPA.

Spontaneous abortion (SA) is the loss of the conceptus before 22 weeks of gestation when fetal weight is less than 500 g. The genetic etiology accounts for more than two third of SA, and autosomal aneuploidies alone account for up to 70% fetal loss. The aim of this study was to highlight the most common chromosomal causes of fetal loss. In this study, 220 products of abortion and in utero fetal death were analyzed by using FISH (AneuVysion) on interphase nuclei from chorionic villus and by using MLPA (SALSA P036, P070 and P245 kits) on DNA extracted from fetal tissues. The gestational age ranged from the 7th to the 38th week of gestation. Of a total of 151 samples analyzed by using FISH, 10 chromosomal abnormalities were observed: four trisomies 21 (one of them was mosaic), a trisomy 18, a trisomy 13, three triploidies and one monosomy X (Turner). From the additional 69 samples analyzed by using MLPA, two anomalies were found: two monosomies X (Turner). FISH and MLPA are simple, rapid and sensitive tools for the detection of chromosomal aneuploidies. Avoiding the cell culture step necessary for karyotyping, they represent very interesting alternative methods to diagnose genomic disorders in products of abortion in which poor sample quality often leads to cell culture failure.

De novo unbalanced translocation 2;4 characterized by metaphase CGH and array CGH in a child with mental retardation and dysmorphic features.

BACKGROUND: It is known from postnatal diagnosis that imbalances of the subtelomeric regions contribute significantly to idiopathic mental retardation. PATIENT AND METHODS: We report a case of a 4-year-old child with growth retardation, minor physical abnormalities, hypotonia and developmental delay associated with a derivative chromosome 4. Molecular cytogenetic investigations were performed to characterize the chromosomal rearrangement. RESULTS: Multi fluorescence in situ hybridization revealed the presence of chromosome 2 material on the derivative chromosome 4. Metaphase comparative genomic hybridization detected a terminal 4q34 deletion. Array CGH analysis could precise breakpoints with duplication 2q36 → qter. The clinical phenotype was similar to those described in cases with a trisomy 2qter. CONCLUSION: This study emphasizes the value of array CGH to detect or characterize chromosome rearrangements in mentally retarded patients. Unlike metaphase CGH, the high resolution of array CGH in subtelomeric regions allows an accurate description of chromosomal aberrations.