Chromosome abnormalities due to maternal translocations not detected with routine amniocentesis

Abstract

Individuals carrying balanced translocations may have offspringwith unbalanced karyotypes. This may result in symptoms ranging from mild to severe mental retardation with multiple congenital defects depending, on the chromosomes involved. We are reporting two very interesting chromosomal abnormalities detected postnatally, after the infants were referred for genetic evaluation. Both mothers had amniocentesis: the first because of abnormalities detected on ultrasound and the second because of a previous child with anomalies and because of advanced maternal age. The first was interpreted as showing a balanced translocation and the second as normal. The first case involves a child whose mother carried a 3 way reciprocal translocation. The child inherited 2 of the 3 maternal derivatives resulting in an unbalanced chromosome complement, which in turn created multiple congenital anomalies that were incompatible with life. The second child's mother had a reciprocal translocation involving chromosomes 19 and 21. The child inherited an abnormal chromosome 21, a derivative secondary to the maternal translocation. This abnormality resulted in both a deletion of a part of the long arm of chromosome 21 and a duplication of a portion of the long arm of chromosome 19. Reevaluation of the chromosome analysis obtained by amniocentesis from the first pregnancy in which the child had a diaphragmatic hernia showed the same chromosome abnormality. Both abnormalities were identified postnatally with the use of FISH. This case illustrates the importance of careful genetics follow up of infants with anomalies.