Genetic analysis of a case of ring chromosome 18 child and literature review HUANG Bingyi, ZHAO Qin, YU Donglan, WANG Manyi, ZHU Chunjiang. (Genetics and Precision Medicine Laboratory, the Affiliated Hospital of Guilin Medical University, Guilin 541001, Guangxi, China)
Abstract: Objective To conduct a genetic analysis on a child with mental decline and delayed growth and development, and to analyze the relationship between clinical phenotype and genetic characteristics. Methods The clinical data from the patient with mental decline and delayed growth and development were collected. G-banding karyotype analysis and copy number variation sequencing (CNV-seq) were
performed. Using "ring chromosome 18" as the keyword, the papers included in China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform and PubMed were searched from January 1998 to October 2024. The clinical manifestations and chromosomal karyotype analysis results of patients with ring chromosome 18 were summarized. Results The child had a distinctive facial
appearance，and the chromosomal karyotype analysis result was 46, XY, r (18) (p11.21q23) . The CNV-seq result was seq[hg19]del ( 18 ) ( p11.32p11.21 ) chr18: g.120000_14980000del, indicating a 14.86 Mb copy number deletion in the 18p11.32p11.21 region, diagnosed with ring chromosome 18. The chromosomal karyotypes of the child's parents were both normal. A total of 16 papers on ring chromosome 18 were searched ( 16 cases ) . Among the 17 patients, distinctive facial appearance accounted for 100.00% ( 17/17 ) , mental decline accounted for 93.75% ( 15/16, excluding one prenatally diagnosed fetus ) , language and behavioral delays accounted for 64.71% ( 11/17 ) , short stature accounted for 52.94% ( 9/17 ) , neurodevelopmental abnormalities accounted for 41.18% ( 7/17 ) , microcephaly accounted for 17.65% ( 3/17 ) , cardiac anomalies accounted for 23.53% ( 4/17 ) , endocrine and immune system abnormalities accounted for 17.65% ( 3/17 ) , hypotonia accounted for 17.65% ( 3/17 ) , ocular abnormalities accounted for 17.65% ( 3/17 ) , epilepsy accounted for 11.76% ( 2/17 ) , gonadal dysgenesis accounted for 11.76% ( 2/17 ) , and skin lesions accounted for 5.88% ( 1/17 ) . Conclusions Children with ring chromosome 18 may present with manifestations such as delayed growth and development, mental decline, distinctive facial appearance, neurodevelopmental abnormalities and cardiac anomalies. Their clinical phenotypes are related to the location of the chromosome deletion and the size of the deleted segment.
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