Connective tissue is the material between the cells of the body that gives tissues form and strength. This "cellular glue" is also involved in delivering nutrients to the tissue, and in the special functioning of certain tissues. Connective tissue is made up of dozens of proteins, including collagens, proteoglycans, and glycoproteins. The combination of these proteins can vary between tissues. The genes that encode these proteins can harbor defects or mutations, which can affect the functioning of certain properties of connective tissue in selected tissues. This can lead to a HDCT.