A Rare De Novo Robertsonian Translocation t(21q; 21q) in an Iranian Child With Down Syndrome: A Case Report

Down syndrome or trisomy 21 is the most common genetic disorder with a prevalence of 1 in 700 live-born infants. It is characterized by the intellectual disability of varying range, developmental delay, distinctive facial features and various physical abnormalities. The most frequent clinical features include hypotonia, short stature, short neck, upward slanting eyes, flat nasal bridge, bulging tongue, small ears and a single palmar crease of the hands. Mainly there are three cytogenetic forms of Down syndrome including free trisomy 21, mosaicism and Robertsonian translocation. We describe the case of a 1-year-old Iranian female child who presented to our genetic counseling center with intellectual and physical disabilities. The most common features of Down syndrome were present. The cytogenetic analysis confirmed the diagnosis, with detection of the Robertsonian translocation t(21q; 21q). The patient s parents were found to be both phenotypically and cytogenetically normal, so the identified Robertsonian translocation t(21q; 21q) probably have arisen de novo.