唐氏综合征（DS）是由于21号染色体的额外拷贝而发生的。大约3%的唐氏综合征病例是由罗伯逊易位引起的，最常见的是t(14；21)，其他类型的易位是该综合征非常罕见的原因。道路交通事故后，一名10岁的智力低下患者入院。病人肌肉松弛,延迟了英里的石头，发育迟缓的年龄，眼睛倾斜，扁平鼻梁,不合格的演讲。在细胞遗传学分析中，患者的核型显示一条正常的21号染色体和一条罗伯逊易位t（21;21）。患者的父母和兄弟姐妹表型正常。罗伯逊易位t（21;21），可以通过从载波父级传输来发生，由于罗伯逊易位的卵巢镶嵌或可能从头出现。在目前的情况下，父母的核型正常，兄弟姐妹的表型正常，罗伯逊易位可能是从头出现的。本病例是唐斯综合征，罗伯逊易位t（21;21）可能从头出现。
Downs syndrome (DS) occurs due to an extra copy of chromosome 21. About 3% of cases of Downs syndrome occur due to Robertsonian translocation, most commonly t (14; 21), other types of translocations are very rare cause of the syndrome. A 10-year-old patient with mental retardation was admitted following road traffic accident. Patient had flabby muscles, had delayed mile stones, stunted growth for the age, slanting of eyes, flat nasal bridge, and ineligible speech. On cytogenetic analysis the patient had karyotype showing one normal chromosome 21 and one Robertsonian translocation t (21; 21). Parents and siblings of the patient were phenotypically normal. Robertsonian translocation t (21; 21), can occur by transmission from carrier parent, due to ovarian mosaicism for Robertsonian translocation or may appear de novo. In the present
case as the parents had normal karyotype and siblings were phenotypically normal, Robertsonian translocation probably have arisen de novo. The present
case was a
case of Downs syndrome with Robertsonian translocation t (21;21) probably arising de novo.
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