Two Cases With De Novo 21/21 Translocation Down Syndrome: Review of Literature

Abstract

Down Syndrome (DS), is the most common chromosomal aneuploidy and also the most common genetic reason of mental retardation. It is generally characterized by an extra chromosome 21. The incidence is 1:1000. Usually, there is no phenotypic difference between complete trisomy 21 and translocation trisomy 21. Two patients were sent to our laboratuary of medical genetics because of clinical features of DS. Conventional cytogenetic techniques were performed for these patients. The karyotypes were found as 46,XY, rob(21)(q10q10) and 46,XX, rob(21)(q10q10). The karyotypes of the parents were normal. The risk of the translocation DS can be estimated by analysing the translocated chromosome in both of the parents. Chromosomal analysis, family history, pedigree, ages and karyotypes of the parents are the basic factors at estimating the risks. In this study, the clinical features and genetic counselling of the translocation trisomy 21 are presented based on the literature.

Keywords

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De Novo 21/21 Translokasyonu Olan Down Sendromlu İki Olgu: Literatür Araştırması

Abstract

Down sendromu, en yaygın kromozomal anöploidi olup mental retardasyonun en sık rastlanan genetik nedenidir. Çoğunlukla ekstra kromozom 21 varlığı ile karakterizedir. Sıklığı yaklaşık olarak 1000 canlı doğumda birdir. Genellikle klasik trizomi ve translokasyon tipi Down sendromu arasında fenotipik farklılık bulunmamaktadır. Klasik Down sendromu şüphesiyle laboratuarımıza gönderilen iki hastanın, konvansiyonel sitogenetik tekniklerle incelemeleri yapıldı. Sitogenetik analiz sonucunda hastaların karyotipleri 46,XY, rob(21)(q10q10) ve 46,XX, rob(21)(q10q10) olarak tespit edildi. Ebeveynlerinin karyotipleri normaldi. Translokasyon tipi Down sendromu riski, ebeveynlerin her ikisinde de translokasyonlu kromozomun varlığı araştırılarak tahmin edilebilir. Kromozomal çalışma, aile hikayesi, pedigri analizi, parental yaşlar ve parental karyotipler genetik danışmanlık ve sonraki gebelik için risk tahmininde temel faktörlerdir. Bu çalışmada da Robertsonian translokasyon tipi Down sendromlu hastaların klinik özellikleri ve genetik danışmanlık süreci literatür bilgileri ışığında değerlendirilerek sunulmuştur.

Keywords

• Down sendromu, sitogenetik analiz, translokasyon, genetik

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