Monosomy 1p36 syndrome is one of the most common submicroscopic deletion syndromes, which is characterized by the presence of delayed developmental milestones, intellectual disability, and clinically recognizable dysmorphic craniofacial features. The syndrome comprises 4 cytogenetic groups including pure terminal deletions, interstitial deletions, complex rearrangements, and derivative chromosomes 1 due to unbalanced translocations, where unbalanced translocations represent the least percentage of all cases of monosomy 1p36 (7%). Most patients with monosomy 1p36 due to an unbalanced translocation can be cytogenetically diagnosed using conventional techniques. However, chromosomal microarray analysis is mandatory in these cases to detect copy number variance and size of the deletion and allows for setting a phenotype-genotype correlation. Here, we studied a 1.5-year-old female patient who showed intellectual disability, delayed milestones, hypotonia, seizures, and characteristic dysmorphic features including brachycephaly, straight eyebrows, deep-set eyes, downslanting palpebral fissures, midface hypoplasia, depressed nasal bridge, long philtrum, and pointed chin. Conventional cytogenetic analysis (CCA), microarray study, and fluorescence in situ hybridization (FISH) analysis were performed. CCA showed a translocation involving chromosomes 1 and 21, 45,XX,der(1)t(1;21)(p36.32;q21.1)dn. Microarray analysis revealed copy number losses at both 1p36 and proximal 21q. FISH confirmed the presence of the 1p36 deletion, but was not performed for 21q. We have concluded that phenotype-genotype correlation for monosomy 1p36 syndrome can be performed for the fundamental clinical manifestations; however, the final aspect of the syndrome depends on composite factors. Monosomy 1p36 due to unbalanced translocation may present either classically or with additional altered features of various severity based on the copy number variations involving different chromosomes.
Mol Syndromol

中文翻译：

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一例不平衡易位引起的1p36单体综合征的表型和分子细胞遗传学分析

Monosomy 1p36综合征是最常见的亚显微缺失综合征之一，其特征是存在发育迟缓的里程碑，智力残疾和临床上可辨认的颅面畸形。该综合征包括4个细胞遗传学组，包括纯末端缺失，间质缺失，复杂的重排和由于不平衡易位引起的衍生染色体1，其中不平衡易位占所有单体性1p36病例的最小百分比（7％）。可以使用常规技术在细胞遗传学上诊断大多数因易位不平衡而导致1p36单体性的患者。但是，在这些情况下必须进行染色体微阵列分析，以检测拷贝数变异和缺失大小，并允许设置表型与基因型的相关性。这里，我们研究了一名1.5岁的女性患者，该患者表现出智力残疾，里程碑时间延迟，肌张力低下，癫痫发作和特征性畸形特征，包括头畸形，直眉，深陷眼，睑裂，下颌发育不全，鼻梁凹陷，长发和尖下巴。进行常规的细胞遗传学分析（CCA），微阵列研究和荧光原位杂交（FISH）分析。CCA显示涉及染色体1和21、45，XX，der（1）t（1; 21）（p36.32; q21.1）dn的易位。微阵列分析显示在1p36和近端21q处的拷贝数丢失。FISH确认存在1p36缺失，但未进行21q。我们得出的结论是，可以针对基本的临床表现进行1s36综合征的表型与基因型相关性。然而，综合症的最终方面取决于综合因素。由于涉及不同染色体的拷贝数变异，由不平衡易位引起的单体性1p36可能具有经典特征，也可能具有其他严重程度不同的附加特征。
摩尔综合症