De novo nonsense or frameshift mutations in the AHDC1 gene have been identified as the causative factor for Xia-Gibbs syndrome (XGS, OMIM#615829) in 2014, a neurodevelopmental disorder characterized by intellectual disability and developmental delay (1). Here, AHDC1 is linked to AHDC1-related intellectual disability-obstructive sleep apnea-mild dysmorphism syndrome.