Skeletal Dysplasia-T-Cell Immunodeficiency-Developmental Delay Syndrome, is also known as neuro-immuno-skeletal dysplasia syndrome due to extl3 deficiency. An important gene associated with Skeletal Dysplasia-T-Cell Immunodeficiency-Developmental Delay Syndrome is EXTL3 (Exostosin Like Glycosyltransferase 3). Affiliated tissues include bone and liver, and related phenotypes are global developmental delay and abnormality of the skeletal system