Coexistence of severe developmental delay, epilepsy, and hemangioma in Snijders Blok-Fisher syndrome suggests the presence of a POU3F3-related SNIBFIS endophenotype: A case report.

POU3F3 proteins are eukaryotic transcription factors and contribute to the processes in the development of brain and kidney. Pathogenic POU3F3 variants cause a neurodevelopmental disorder called Snijders Blok-Fisher syndrome (SNIBFIS). This article reports a new SNIBFIS case harboring a novel heterozygous c.1018_1019delCAinsTT (p.Gln340Leu) variant in the POU3F3 gene. This variant affects the α2 helix of POU-S domain and is predicted to be "pathogenic" by multiple in-silico tools. The proband had severe intellectual disability, hypotonia, autistic features, sleep disturbances, and dysmorphic features. The association with epilepsy and hemangioma like two of the three previously reported patients with mutations in the POU-S domain was also a remarkable finding to understand the importance of POU-S domain. This clinical report also highlights the interest of reinterpretation of molecular data and brings a new perspective to the genotype-phenotype relationship in "Snijders Blok-Fisher syndrome".