The odyssey of complex neurogenetic disorders: From undetermined to positive.

The genetic and phenotypic heterogeneity of neurogenetic diseases forces patients and their families into a "diagnostic odyssey." An increase in the variability of genetic disorders and the corresponding gene-disease associations suggest the need to periodically re-evaluate the significance of variants of undetermined pathogenicity. Here, we report the diagnostic and clinical utility of Targeted Gene Panel Sequencing (TGPS) and Whole Exome Sequencing (WES) in 341 patients with suspected neurogenetic disorders from centers in Buenos Aires and Cincinnati over the last 4 years, focusing on the usefulness of reinterpreting variants previously classified as of uncertain significance. After a mean of ±2years (IC 95:0.73-3.27), approximately 30% of the variants of uncertain significance were reclassified as pathogenic. The use of next generation sequencing methods has facilitated the identification of both germline and mosaic pathogenic variants, expanding the diagnostic yield. These results demonstrate the high clinical impact of periodic reanalysis of undetermined variants in clinical neurology.

DEPDC5 mutation and familial focal epilepsy with variable foci: genotype and phenotype of a family.

Familial focal epilepsy with variable foci is a relatively rare autosomal disease with an unclear incidence, which is characterized by focal seizures arising from different cortical regions in different family members. We describe three members of a two-generation Argentine family with familial focal epilepsy with variable foci syndrome and a DEPDC5 gene mutation. The mean onset age was nine years old. The father experienced episodes with occipital semiology and both siblings exhibited frontal lobe seizures. Their neurological examination and neuroimaging studies were normal. All three patients are currently seizure-free, in spite of initially experiencing frequent seizures. Complete exome sequencing revealed a new DEPDC5 gene mutation (NM_001242896: c.4718T>C; p.L1573P). This study of a family with clinical characteristics that met all the criteria for familial focal epilepsy with variable foci demonstrates the usefulness of exome sequencing as a diagnostic tool. [Published with video sequence on www.epilepticdisorders.com].