Abstract

Down syndrome (DS) is the most frequent single chromosome abnormality as well as the most prevalent genetic cause of mental retardation in childhood. DS is usually diagnosed at birth by a recognizable and specific combination of dysmorphism – flat facial profile, upslanting palpebral fissures, epicanthal folds, low nasal bridge, anomalous auricles, simian crease, muscular hypotonia. Although the clinical diagnosis of DS is easy, chromosomal analysis is necessary in each case to confirm the diagnosis for assessment of the genetic implications for  the family. The aim of this study was to describe the cytogenetic variability of DS in Estonia, and the prevalence of dysmorphic features and associated anomalies and diseases in Estonian patients.
Methods and patients. We investigated 172 patients from institutions of disabled children/persons, from Down syndrome support groups or from genetic consulting centres. Medical records or questionnaires for the parents of the patients, with special attention to anomalies and diseases, were analysed and on the basis  of these data a special study protocol was completed. For inclusion in the study, cytogenetic diagnosis with confirmation of DS was needed.
Results. As two study subjects (2/172) had a normal karyotype, the study group was formed of 170 DS patients. This means that our pediatricians have adequate qualification to recognize the condition. The results of cytogenetic investigations were in good correlation with the literature data: regular trisomy was found in 90%, translocation in 6.5% and mosaicism in 3.5% of  the patients. The prevalence of dysmorphic features was also in quite good correlation with the results of other studies, however, congenital anomalies and associated illnesses were less frequent in our study than reported by other authors. The reason for this is unclear and requires further investigation.
Conclusion. To improve the quality of life and medical care of persons with DS, guidelines should be developed for management of DS in Estonia.