CDKL5 and craniodiaphyseal dysplasia: Cyclin‐dependent kinase‐like 5 (CDKL5) is a poorly characterized protein kinase, which is mutated in a rare, debilitating condition known as CDKL5 deficiency disorder (CDD; OMIM 300203; 300672) (Kalscheuer et al, 2003; Fehr et al, 2013).