An increased burden of rare exonic variants in NRXN1 microdeletion carriers is likely to enhance the penetrance for autism spectrum disorder.

Autism spectrum disorder (ASD) is characterized by a complex polygenic background, but with the unique feature of a subset of cases (~15%-30%) presenting a rare large-effect variant. However, clinical interpretation in these cases is often complicated by incomplete penetrance, variable expressivity and different neurodevelopmental trajectories. NRXN1 intragenic deletions represent the prototype of such ASD-associated susceptibility variants. From chromosomal microarrays analysis of 104 ASD individuals, we identified an inherited NRXN1 deletion in a trio family. We carried out whole-exome sequencing and deep sequencing of mitochondrial DNA (mtDNA) in this family, to evaluate the burden of rare variants which may contribute to the phenotypic outcome in NRXN1 deletion carriers. We identified an increased burden of exonic rare variants in the ASD child compared to the unaffected NRXN1 deletion-transmitting mother, which remains significant if we restrict the analysis to potentially deleterious rare variants only (P = 6.07 × 10-5 ). We also detected significant interaction enrichment among genes with damaging variants in the proband, suggesting that additional rare variants in interacting genes collectively contribute to cross the liability threshold for ASD. Finally, the proband's mtDNA presented five low-level heteroplasmic mtDNA variants that were absent in the mother, and two maternally inherited variants with increased heteroplasmic load. This study underlines the importance of a comprehensive assessment of the genomic background in carriers of large-effect variants, as penetrance modulation by additional interacting rare variants to might represent a widespread mechanism in neurodevelopmental disorders.

Neuropsychological implications of adjunctive levetiracetam in childhood epilepsy.

INTRODUCTION: Levetiracetam (LEV) is an effective antiepileptic drug also used in childhood and adolescence. Literature data regarding the long-term effects of LEV in childhood epilepsy and based on extensive neuropsychological evaluations using standardized tools are still scanty. Our study aimed to address this topic. MATERIALS AND METHODS: We studied 10 patients with epilepsy characterized by focal or generalized seizures (4 boys, 6 girls; mean age: 10 years 8 months; range: 6 years 2 months - 16 years 2 months), treated with adjunctive LEV during a follow-up of 12 months. In 6 patients electroencephalogram (EEG) showed continuous spike and waves during sleep. Using standardized tools, we performed seriated assessments of cognitive and behavioral functioning in relation to seizure and EEG outcome. RESULTS: Six patients completed the trial after 12 months of treatment; 1 patient dropped out of the study after 9 months, 3 patients after 6 months. Adjunctive LEV was effective on seizures in 3/10 patients and on EEG in 2/10 patients, and was well tolerated in all examined cases. Overall, no worsening of cognitive or behavioral functions has been detected during the period of the study; even at 6 and 12 months from baseline, an improvement in patients' abstract reasoning has been found, that was not related to seizure or EEG outcome. CONCLUSIONS: In our population of children and adolescents, LEV had no adverse cognitive or behavioral effects, short- or long-term. We found an improvement of abstract reasoning, regardless of seizure and EEG outcome.