Maia, NNabais Sá, Maria JoãoOliveira, CláudiaSantos, FláviaSoares, Celia APrior, CatarinaTkachenko, NataliyaSantos, Rosáriode Brouwer, Arjan P. M.Jacome, ArianaPorto, BeatrizJorge, Paula2023-10-242023-10-242021-12Maia N, Nabais Sá MJ, Oliveira C, et al. Can the Synergic Contribution of Multigenic Variants Explain the Clinical and Cellular Phenotypes of a Neurodevelopmental Disorder?. Genes (Basel). 2021;13(1):78.doi:10.3390/genes130100782073-4425http://hdl.handle.net/10400.16/2840We describe an infant female with a syndromic neurodevelopmental clinical phenotype and increased chromosome instability as cellular phenotype. Genotype characterization revealed heterozygous variants in genes directly or indirectly linked to DNA repair: a de novo X-linked HDAC8 pathogenic variant, a paternally inherited FANCG pathogenic variant and a maternally inherited BRCA2 variant of uncertain significance. The full spectrum of the phenotype cannot be explained by any of the heterozygous variants on their own; thus, a synergic contribution is proposed. Complementation studies showed that the FANCG gene from the Fanconi Anaemia/BRCA (FA/BRCA) DNA repair pathway was impaired, indicating that the variant in FANCG contributes to the cellular phenotype. The patient's chromosome instability represents the first report where heterozygous variant(s) in the FA/BRCA pathway are implicated in the cellular phenotype. We propose that a multigenic contribution of heterozygous variants in HDAC8 and the FA/BRCA pathway might have a role in the phenotype of this neurodevelopmental disorder. The importance of these findings may have repercussion in the clinical management of other cases with a similar synergic contribution of heterozygous variants, allowing the establishment of new genotype-phenotype correlations and motivating the biochemical study of the underlying mechanisms.engDNA repair pathwayschromosome instabilityneurodevelopmental disorderjournal article10.3390/genes13010078