[Clinical features analysis of 9 children with ring chromosome syndrome]

Objective: To analyze the clinical features and diagnostic process of ring chromosome syndrome. Methods: Clinical data of 9 children with ring chromosome syndrome who were treated at the Children's Medical Center of Peking University First Hospital from September 2009 to May 2025, were summarized and analyzed in a case series study. The data included clinical manifestations, types of epileptic seizures, genetic testing, treatment outcomes, and follow-up results, et al. Results: Among the 9 children with ring chromosome syndrome, there were 6 girls and 3 boys, including 4 children with ring chromosome 20 syndrome, 3 children with ring chromosome 14 syndrome, and 1 child each with ring chromosome 13 and 17 syndrome. All 9 children had de novo chromosomal variations. Among them, 3 children of ring chromosome 20 syndrome were mosaic, and the remaining 6 children were non-mosaic. All 9 children exhibited diverse clinical features, especially those with ring chromosome 20 syndrome, which presented with specific manifestations. The 4 children with ring chromosome 20 syndrome all had acute epileptic seizures as the initial symptom, with onset ages of 67, 39, 17, and 96 months, and all had focal seizures. One child with ring chromosome 20 syndrome had non-convulsive status epilepticus. Development of all 4 children with ring chromosome 20 syndrome was normal before seizure onset, but 3 children showed regression after onset. No physical deformities were observed in 4 children with ring chromosome 20 syndrome, and 2 children were misdiagnosed, 3 children underwent whole exome sequencing and copy number variation analysis in their families, with no abnormalities detected. All 4 children with ring chromosome 20 syndrome were diagnosed through chromosomal karyotype analysis, the intervals between onset and diagnosis were 2, 81, 19 and 13 months, respectively. Follow-up showed that epileptic seizures were not controlled in all 4 children with ring chromosome 20 syndrome. The other 5 children were characterized by developmental delay as the initial symptom, followed by epileptic seizures between 3 and 24 months of age. Developmental regression of the other 5 children did not occur after onset, 2 of them had microcephaly, and 3 had wide-set eyes. No misdiagnoses were reported in these 5 children, and the intervals between onset and diagnosis were 7, 3, 55, 3, and 106 months, respectively. Follow-up showed that epileptic seizures were controlled in these 5 children. Conclusions: Ring chromosome 20 syndrome typically manifest with epilepsy as the initial symptom and are refractory to drug treatment, their early development is entirely normal. Ring chromosome 13, 14, and 17 syndrome are characterized by developmental delay from an early age, followed by the onset of epileptic seizures, which are easily controlled. Conventional whole-exome sequencing and copy number variation analysis in families rarely detect ring chromosome abnormalities. Early chromosomal karyotype analysis is essential for the diagnosis of ring chromosome syndrome.