Importantly, PDE4D has been implicated in cognitive ability with the observations that (i) missense mutations of PDE4D cause rare neurodevelopmental disorder with intellectual disabilities (Acrodysostosis type 2) and (ii) PDE4D plays a role in regulating levels of cAMP which is an important neurobiological substrate of learning and memory early in development. This evidence concerns the gene PDE4D and neurodevelopmental disorder.