In this study, we assessed the frequency of GABRG2 mutations in a large cohort of families with FS and reported pathogenic mutations in 6/108 (5.6%) families. First, we identified a GABRG2 disease-causing mutation (p.Glu402fs*3) in a multiplex family with FS and TLE, in which linkage analysis previously suggested a possible digenic inheritance on 1q25-q31 and 18qter.19 However, with the finding of a clear pathogenic mutation in GABRG2, leading to the introduction of a premature stop codon (p.Glu402fs*3), both loci were unlikely to cause the phenotype. This study provides a clear example of the limitation of linkage analysis and how phenocopies can distort linkage results (1 affected member of the large family did not carry the GABRG2 mutation). Unbiased next-generation sequencing approaches will undoubtedly unveil additional erroneous genetic claims in the literature. In the follow-up cohort consisting of 107 families with FS (with or without subsequent epilepsy), we identified 2 other frameshift mutations (p.Val462fs*33 and p.Pro59fs*12), 1 nonsense mutation (p.Arg136*), 1 missense mutation (p.Met199Val), and 1 deletion (exons 1–4) in the GABRG2 gene. Most patients carrying a GABRG2 mutation had a
