Our study outlines the discovery of a novel null mutation in the HERC2 gene, which is a significant advance in delineating the broad range of neurodevelopmental conditions that are caused by mutations in this gene. We describe a family with children affected with a very severe developmental disorder, causing paediatric lethality in two individuals. The HERC2 protein mediates the tagging of other proteins that are destined for a fundamental process of regulated disposal in cells. In patient cells that lack HERC2 protein, our data suggests that disruptions in protein disposal include other cellular functions such as DNA damage response and mitochondrial function. This provides insight into disease mechanism for HERC2-related disorders. Our genetic findings should improve clinical diagnosis and management of previously undiagnosed cases with developmental delay. (By Dr Marilena Elpidorou, https://jmg.bmj.com/content/early/2020/06/22/jmedgenet-2020-106873 )