The Importance of Down Syndrome Phenocopies in the Newborns in Tertiary Obstetric Hospital

Background: A phenotype is the composite of the observable characteristics, and in some cases it is not representative for identification of recognized genetic structure. Aim: The aims of the study were to present the incidence and clinical features of dismorphia in newborn children, and to investigate the prevalence of phenocopies among them. Material and Methods: Newborns born at the University Clinic for Gynecology & Obstetrics, having at least 3 minor anomalies (mm) specific for Down syndrome were investigated. Patients’ histories, observation, cytogenetic analysis of peripheral blood samples were analysed. Results: Among 17835 liveborns during 5 years’ period, 128 were detected having at least 3 mm, calculated incidence of dysmorphia 0.83% (1:139). Cytogenetic analysis was not performed in 3.1% (4/128) due to immediate death or transfers elsewhere, 30.5% (39/128) were confirmed Down syndrome. Cytogenetic analysis showed trisomy 21 in 97.4%; Robertsonian translocation had one newborn (2.6%); normal cytogenetic structure had 66.4% (85/128) of the newborns. Conclusons: Other studies didn’t highlight the proportion of phenocopies of Down syndrome in unselected population of newborns, mainly investigating sick children, disabled, or older-aged. As more the critical role of phenocopy emerges, the more the initial difficulty in detecting gene-gene interactions is amplified. Neglecting the possible presence of phenocopies in complex traits, heavily affects the analysis of their genetic data