EXTL3 gene defects are the cause of a multisystem disorder defined as immune-skeletal dysplasia with neurodevelopmental abnormalities.
The main clinical features consist of skeletal dysplasia and mild-to-severe neurodevelopmental delay. These manifestations are universal. Skeletal abnormalities consist of severe platyspondyly resulting in disproportionate short stature with progressive kyphosis. Other skeletal features may include cervical malformations, limb shortening, and brachydactyly.
About half of the patients may exhibit a T-, B+, NK+ severe combined immune deficiency (SCID) phenotype in the first month of life, but later showed partial recovery of T-cell count and function, and mounted normal antibody responses to killed and live vaccines.
EXTL3