Exome sequencing in Nigerian children with early-onset epilepsy syndromes

Nigeria, along with other Sub-Saharan African countries, bears the highest burden of epilepsy worldwide. This high prevalence is attributed to a combination of factors, including a significant incidence of infectious diseases, perinatal complications, and genetic etiologies. Genetic testing is rarely available and is not typically included in the routine diagnostic work-up for individuals with infantile and childhood epilepsy syndromes in these regions. Exome sequencing (ES) offers a diagnostic yield of 24%-62%, but these figures primarily reflect data from high-income countries (HICs) and may not be applicable to low- and middle-income countries (LMICs). In this study, we employed ES to investigate the genetic basis of early-onset epilepsy in 22 affected children from Nigeria.

The study involved sampling of patients diagnosed with early-onset epilepsy syndromes at the Lagos State University Teaching Hospital (LASUTH) Neurology clinic. Venous blood samples were collected, and genomic DNA was isolated and purified. Molecular analysis included DNA fragmentation, ligation, target enrichment, library preparation, and whole-exome sequencing. Computational analysis involved variant calling, curation, and classification using specialized tools and databases.

Pathogenic variants were identified in 6 out of 22 individuals, equaling a diagnostic yield of 27.3% and comprising variants in BPTF, NAA15, SCN1A, TUBA1A and twice in CACNA1A.

In this study, we present the first exome study on early-onset epilepsy syndromes from West Africa, facilitated by a Nigerian-German research collaboration. Our findings reveal a genetic diagnostic yield comparable to that of HICs. The integration of genomic medicine into epilepsy management in Nigeria holds promising prospects for improving patient care and reducing mortality rates.

This study represents the first published exome findings in Nigerian children with early-onset epilepsy, revealing a genetic diagnosis in 27% of cases. Pathogenic variants were identified in five genes amongst 6 of 22 patients, underscoring the potential of genetic testing to enhance epilepsy management in developing nations like Nigeria.