Report of unbalanced chromosomal aberration with translocation (3;6) and partial trisomie 3 as well as partial monosomie 6

Introduction: Translocations occur approximately 1 in 500 newborns. Individuals who carry balanced translocations produce in 50% unbalanced gametes. In the reported case the resulting phenotype almost always includes developmental delay and congenital anomalies.

Case presentation: The 32-years-old pregnant female, gravida 3, para 1, was referred to our prenatal clinic at the gestational age of 14 weeks for chorionic villous biopsy. The previous obstetric history included an uneventful first pregnancy and healthy child. In her second pregnancy the fetus was diagnosed with hydrocephalus at gestation of 20 weeks. Invasive testing showed an unbalanced chromosomal anomaly (46, XX, add6, p25). After counselling a termination was performed. The genetic testing showed a balanced translocation in the child father (46,XY, t(3;6)(p22; p25)). Now in the ongoing third pregnancy the couple presented for chorionic villi sampling (CVS). On ultrasound examination of the fetus we found a prominent posterior fossa as seen in Dandy-Walker complex as well as a dilated third ventricle.

Results: The CVS analysis revealed unbalanced structural chromosomal aberration (46,XY,der(6)t(3;6)(p21,p25)pat. Induced abortion was performed and underwent unremarkably followed by instrumental placental delivery. The pathologic examination of the fetus showed beside the cerebral abnormality, presence of cleft lip and palate, pseudotruncus arteriosus with ventricular septum defect, hypertelorism, and facial dysmorphism.

Conclusion: In case of index Patient (the fetus with Hydrocephalus) early ultrasound examination in pregnancy can lead to early diagnosis of a suspected recurrence of chromosomal anomaly, particularly with carriers of balanced translocation.

chromosomal aberration - translocation - ultrasound