Bilateral Perisylvian Polymicrogyria, Intellectual Disability and Nephronophthisis Associated With Compound Heterozygous Pathogenic Variants in the CEP83 Gene.

The centrosomal protein 83 (CEP83) is a centriolar protein involved in primary cilium assembly, an early and critical step in ciliogenesis. Bi-allelic pathogenic variants in the CEP83 gene have been associated with infantile nephronophthisis and, in a few patients, retinitis pigmentosa. We describe a 5-year-old boy with bilateral perisylvian polymicrogyria, intellectual disability, and nephronophthisis in whom, using exome sequencing, we identified the c.1052T>G p.(Leu351*) stopgain variant inherited from the father and the c.2024T>C p.(Leu675Pro) missense variant inherited from the mother, in a compound heterozygous pattern. Polymicrogyria or, in general, malformations of cortical development had not been previously observed in patients with pathogenic CEP83 variants. However, defects in CEP83 can affect the formation and function of cilia or centrosomal structures, resulting in a polymicrogyric pattern overlapping with that associated with pathogenic variants affecting other genes coding for centrosomal components. This observation expands the spectrum of phenotypes associated with the CEP83 gene and adds it to the list of genes associated with bilateral perisylvian polymicrogyria.

Familial dominant epilepsy and mild pachygyria associated with a constitutional LIS1 mutation.

We describe a mother and son with focal epilepsy, mild cognitive impairment, and pachygyria, which was parieto-occipital in the mother and with remarkable posterior greater than anterior severity in the son. Overall clinical manifestations, although overlapping in type, were likewise slightly more severe in the son. Using targeted resequencing through a gene panel for malformations of cortical development, we identified the c.655 T > A [p.(Trp219Arg)] novel missense variant in the LIS1 gene, segregating in the proband and in his mother. Western Blot analysis, qPCR gene expression and RT-PCR disclosed no significant differences between proband, his parents, and controls. Epilepsy and mild cognitive impairment can be the only clinical presentation of constitutional LIS1 mutations, which can therefore be inherited if the associated phenotype implies limited or no reproductive disadvantage. Parents of patients harboring LIS1 mutations should be assessed for their mutation carrier status.

Diagnostic Targeted Resequencing in 349 Patients with Drug-Resistant Pediatric Epilepsies Identifies Causative Mutations in 30 Different Genes.

Targeted resequencing gene panels are used in the diagnostic setting to identify gene defects in epilepsy. We performed targeted resequencing using a 30-genes panel and a 95-genes panel in 349 patients with drug-resistant epilepsies beginning in the first years of life. We identified 71 pathogenic variants, 42 of which novel, in 30 genes, corresponding to 20.3% of the probands. In 66% of mutation positive patients, epilepsy onset occurred before the age of 6 months. The 95-genes panel allowed a genetic diagnosis in 22 (6.3%) patients that would have otherwise been missed using the 30-gene panel. About 50% of mutations were identified in genes coding for sodium and potassium channel components. SCN2A was the most frequently mutated gene followed by SCN1A, KCNQ2, STXBP1, SCN8A, CDKL5, and MECP2. Twenty-nine mutations were identified in 23 additional genes, most of them recently associated with epilepsy. Our data show that panels targeting about 100 genes represent the best cost-effective diagnostic option in pediatric drug-resistant epilepsies. They enable molecular diagnosis of atypical phenotypes, allowing to broaden phenotype-genotype correlations. Molecular diagnosis might influence patients' management and translate into better and specific treatment recommendations in some conditions.