2458_2459delCT), and Koifman’s research group used chromosome microarray analysis and PCR technology to identify a 141.46 kb homozygous deletion in TRAPPC9, resulting in severe DD and agenesis of the corpus callosum (Koifman et al., 2010; Masih et al., 2022). The gene discussed is TRAPPC9; the disease is dentin dysplasia.