Trisomy 21 is the most common chromosomal aneuploidy in humans with a frequency of about 1:700 live births. Free trisomy 21 constitutes about 95% of all cases, also known as standard Down syndrome. Nonclassic trisomies constitutes 5% and within this group almost half have 14/21 while the remainder carry 21/21, 15/21, and other Robertsonian translocations and mosaic trisomies. Although there are no phenotypic differences between standard and translocation trisomy 21, the latter could be the result of the possibility that one of the parents is a carrier for translocation. Therefore, parents karyotypes should be evaluated in such cases.
In this study, we report the process of diagnosis, comorbid conditions, and genetic counseling in two newborn patients with Down syndrome in the light of current literature.
Key words: Trisomy 21; Translocation; Genetic Counseling.
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