The smallest reported deletion is of 880 kb encompassing SLC25A13 and part of DYNC1I1, but leaving DLX5 and DLX6 intact.3 In the developing limb, both Dlx5 and Dlx6 are thought to be regulated by the transcription factor tumour protein p634 and TP63 mutations cause split-hand/split-foot malformation 4 (SHFM4; OMIM #605289). The gene discussed is TP63; the disease is split hand-foot malformation 4.