Since the advent of exome sequencing studies, causative mutations have been described in the TLDc proteins Tre2/Bub2/Cdc16 (TBC)1 domain family member 24 (TBC1D24) and oxidation resistance 1 (OXR1) in a range of NDD, some characterised by seizures and neurodegeneration as well as developmental delay [15–17]. This evidence concerns the gene OXR1 and Global developmental delay.