A De Novo Xp11.23 Duplication in a Girl with a Severe Phenotype: Expanding the Clinical Spectrum

Impact of copy number variants in epilepsy plus neurodevelopment disorders

INTRODUCTION

Epilepsy, a neurological disorder characterized by recurring unprovoked seizures due to excessive neuronal excitability, is primarily attributed to genetic factors, accounting for an estimated 70 % of cases. Array-comparative genomic hybridization (aCGH) is a crucial genetic test for detecting copy number variants (CNVs) associated with epilepsy. This study aimed to analyze a cohort of epilepsy patients with CNVs detected through aCGH to enhance our understanding of the genetic underpinnings of epilepsy.

METHODS

A retrospective cross-sectional study was conducted using the aCGH database from the Genetics Department of the Faculty of Medicine of the University of Porto, encompassing 146 patients diagnosed with epilepsy, epileptic encephalopathy, or seizures. Clinical data were collected, and aCGH was performed following established guidelines. CNVs were classified based on ACMG standards, and patients were categorized into four groups according to their clinical phenotype.

RESULTS

Among the 146 included patients, 94 (64 %) had at least one CNV, with 22 (15.1 %) classified as pathogenic or likely pathogenic. Chromosomes 1, 2, 16, and X were frequently implicated, with Xp22.33 being the most reported region (8 CNVs). The phenotype "Epilepsy and global developmental delay/intellectual disability" showed the highest prevalence of clinically relevant CNVs. Various CNVs were identified across different groups, suggesting potential roles in epilepsy.

CONCLUSIONS

This study highlights the significance of aCGH in unraveling the genetic basis of epilepsy and tailoring treatment strategies. It contributes valuable insights to the expanding knowledge in the field, emphasizing the need for research to elucidate the diverse genetic causes of epilepsy.

Xp11.2 Duplication in Females: Unique Features of a Rare Copy Number Variation

Among the diseases with X-linked inheritance and intellectual disability, duplication of the Xp11.23p11.22 region is indeed a rare phenomenon, with less than 90 cases known in the literature. Most of them have been recognized with the routine application of array techniques, as these copy number variations (CNVs) are highly variable in size, occurring in recurrent and non-recurrent forms. Its pathogenic role is not debated anymore, but the information available about the pathomechanism, especially in affected females, is still very limited. It has been observed that the phenotype in females varies from normal to severe, which does not correlate with the size of the duplication or the genes involved, and which makes it very difficult to give an individual prognosis. Among the patients studied by the authors because of intellectual disability, epilepsy, and minor anomalies, overlapping duplications affecting the Xp11.23p11.22 region were detected in three females. Based on our detailed phenotype analysis, we concluded that Xp11.23p11.22 duplication is a neurodevelopmental disorder.

Chromosomal Microarray Analysis in Children with Unexplained Developmental Delay/Intellectual Disability

Chromosomal microarray (CMA) analysis for discovery of copy number variants (CNVs) is now recommended as a first-line diagnostic tool in patients with unexplained developmental delay/intellectual disability (DD/ID) and autism spectrum disorders. In this study, we present the results of CMA analysis in patients with DD/ID. Of 210 patients, pathogenic CNVs were detected in 26 (12%) and variants of uncertain clinical significance in 36 (17%) children. The diagnosis of well-recognized genetic syndromes was achieved in 12 patients. CMA analysis revealed pathogenic de novo CNVs, such as 11p13 duplication with new clinical features. Our results support the utility of CMA as a routine diagnostic test for unexplained DD/ID.