Prenatal Diagnosis of Cryptic Translocation t(5p;17q) with Fluorescent In Situ Hybridization

Abstract

AbstractReciprocal chromosomal rearrangements, de novo or inherited, often raise a concern about the foetal health and outcome of the affected pregnancies. The size and origin of the translocated chromosomes could be variable. Cryptic translocations often remain undetected and misdiagnosed. Several studies confirmed that there could be a loss of a certain amount of genomic material within breakpoints, which leads to uncertainties in predicting the pregnancy outcome. A 38 year pregnant woman approached our clinic for a genetic counselling. This was her first pregnancy, with normal foetal growth on ultrasound follow up. The amniocentesis was carried out due to the advanced maternal age. Conventional cytogenetic report showed putative deletion of short arm of chromosome 5. Cordocentesis was done additionally at 18 week of pregnancy due to the discrepancy between normal ultrasonographic finding and karyotype result. MLPA analysis showed that 5p critical region was present. FISH has been performed, using 5p;q probe (Cytocell aquarius, Cat No LPU 013), which showed cryptic de novo translocation 46,XX.ish t(5;17) (p15.1;q25). Decision to terminate the pregnancy was made due to the cytogenetic finding and reduced foetal growth recorded after 20th week. Examination at autopsy showed dysmorphism consistent with some features of cri du chat syndrome-micrognathia, hypertelorism, reduced fetal growth, as well as underdeveloped brain for gestational period. Novel technologies in molecular cytogenetics and array techniques could help in detecting minor imbalances and decrease the risk of the birth of malformed fetus. Combination of several prenatal methods -both ultrasonography and novel genetic techniques, in a small number of cases can help in the process of genetic counselling.