TWO SIBLINGS WITH FRAGILE X SYNDROME

Year 2001, Volume: 54 Issue: 3, 241 - 245, 30.09.2001

Ajlan Tükün

Abstract

Th.e fragile X syndrome is the most common spe- cific cause of familial mental retardation. It is asso- ciated with fragility at Xq27.3. Because of varia- tions in route of inheritance and clinical features, ° it can only be diagnosed through genetic studies. However, cytogenetic éxfi›ression levels of fragility in lymphocytes show variation, and r is not always possible to identify affected males with a /ower degree of fragility expression using cytoge- netic techniques.

In this study, two siblings with Martin-Bell phe- notyfiie are reported. A/though they had typical clinical findings and positive family history, fragili- ty at Xq27.3 could not be demonstrated in the first cytogenetic studies. Two years later, in re|oeated cultures of the siblings, 2%- and 5%-fragility was found. The conflicting results of repeated cultures confirmed that the expression variability of fragili- ty might be the reason for false negative cytoge- netic results in affected patients with low fragility ratios.

Keywords

Fra (X)(q27’.3) , Mental Retardation , Manin Bell Phenotype

FRAGİL X SENDROMLU İKİ KARDEŞ

Abstract

Ailesel mental retardasyonu nedenleri arasında ilk sırada yer alan Frajil X sendromu, Xq27.3 böl- gesindeki frajilite ile birliktelik gösterir. Kalıtım ve klinik bulgularındaki değişkenlik nedeni ile kesin tanısı ancak genetik çalışma ile koyulabilir. Ancak, sitogenetik ekspresyon d'üzeyIeri de değişkenlik göstermektedir ve d'üşük eksfiıresyon d‘üzeyi olan hastalara sitogenetik yöntemlerle her zaman ranı koyulamayabilir.
Bu çalışmada, Martin Bell fenotipi gösteren iki olgu sunulmaktadır. Ti|aik klinik bulgularına ve pozitif aile öyk'ûs'üne rağmen ilk sitogenetik ça//şmada Xq27.3’te frajilite gözlenememiş, ancak iki yıl sonra tekrarlanan lenfosit k'üIt'ürIerinde 2% ve 5% oranlarında frajil X sa[:ıtanmıştır. Bu olgu- ların tekrarlanan küIt'ürIerindeki çelişkili sonuçlar, düşük frajilite oranlarına sahip hastalarda frajilite değişkenliğinin yanlış negatif sonuçlara neden ola- bileceğini desteklemektedir

Keywords

Fra (X)(q27’.3) , Mental Retardasyon , Martin Bell Fenotipi

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