Robertsonian Translocation t (21; 21) Offspring of a Balanced Translocation Carrier Parent; an Unfortunate Scenario

A BSTRACT Trisomy of chromosome 21 results in Down Syndrome (DS). It also occurs due to translocation between acrocentric chromosomes, namely 13, 14, 15, and 21. We present this case of a Down Syndrome baby with Robertsonian Translocation (RT) of chromosome 21, born to a balanced RT carrier mother. The proband was an 8-month-old boy with dysmorphism, global developmental delay (GDD), hypospadias, Patent Ductus Arteriosus, and a Simian crease (left). The child was the third born of a non-consanguineous marriage of young parents (35 years father, 25 years mother), with the previous two children deceased. Karyotyping revealed proband: 46, XY,+21, rob (21;21)(q10;q10) Male karyotype with Trisomy 21; mother 46, XX,+21, rob (21;21)(q10;q10). RT carriers are asymptomatic but have a high risk of all pregnancies ending either in spontaneous miscarriage or in the birth of an offspring with DS. This case highlights the importance of genetic testing of parents to rule out balanced translocation carrier status and also the importance of genetic counselling for parents who are desirous of a healthy offspring.