Biallelic pathogenic variants in EXTL3 are associated with neuro-immuno-skeletal dysplasia syndrome, a rare congenital syndrome. EXTL3 encodes for the Exostosin-like 3 protein, a glycosyltransferase that regulates the biosynthesis of heparan sulfate. Pathogenic variants in this gene lead to abnormal glycosaminoglycan concentrations. EXTL3 is involved in the generation of a cellular surface for adhesion properties as well as professional extracellular matrix to let tissue cells bind and grow normally.
The majority of reported pathogenic variants in EXTL3 are missense variants. The variants can be located in any part of the gene, however, most of the pathogenic variants are located in the exostosin domain (amino acids 190-500) or the glycosyl transferase domain (amino acids 663-904).
Variants in EXTL3 can be identified using molecular genetic testing and data should be analysed for a recessive inheritance pattern.
EXTL3