Pallister-Killian syndrome （PKS） is a rare and sporadic genetic disorder due to tissue-limited mosaicism for supernumerary isochromosome 12p（i（12p））, which is usually absent or at low-level mosaicism in cultured lymphocytes but present in fibroblasts. PKS was first described in adults by Pallister in 19771 and later in children by Killian and Teschler-Nicola in 1981.2 An accurate incidence is unknown. It is clinically characterized by profound mental retardation, seizures,hypotonia, supernumerary nipples, pigmentary dysplasia,diaphragmatic hernia, ＂coarse＂ face, including prominent forehead with sparse anterior scalp hair, hypertelorism,short nose with anteverted nares, flat nasal bridge, long philtrum, cleft palate and short neck. Here we report a patient with PKS, who is the first confirmed case with PKS in China's Mainland. Molecular analysis was performed to explore the formation mechanism of i（12p）.The results suggest that the maternal meiosis Ⅱ sister chromatid non-disjunction was likely the first step in the formation of i（12p）, followed by postzygotic mitotic centromeric misdivision.
SHEN Jian-dong LIANG De-sheng ZHOU Zhong-min XIA Yan LONG Zhi-gao WU Ling-qian
为了探究先天性并指畸形的遗传机制,本研究结合临床体格检查、遗传咨询,X线资料、图片等手段,对收治的疑似Ⅰ-c型并指家系(A家系为五代74人家系,其中病人34人)进行了表型鉴定和遗传分析。根据并指畸形(syndactyly,SD)分类标准,该家系表型经判断属于Ⅰ-c型SD和I-a型SD表型,遗传分析表明,供试家系表现度(在一定的环境中,某一突变个体基因型表达的变异程度)具有一定的差异性,外显率(某一基因型个体显示其预期表型的比率)也不完全,属于常染色体显性遗传方式。研究结果进一步暗示,Ⅳ型SD和三节指节拇指一并多指综合征(triphalangeal thumb polysyndactyly syndrome,TPTPS)致病机制具有遗传同质性(同一种疾病临床表现相同,引起疾病的遗传基础不同),表型-基因型分析提示ZRS区(极化活性区(zone of polarizing activity,ZPA)调控序列(ZPA regulatory sequence,ZRS))轻微表型到严重表型过渡具有一定的连续性。我们的研究为并指的遗传机制的揭示和相关疾病的产前诊断、遗传咨询等工作提供了一定的理论依据。
