COL2A1 and Achondrogenesis type 2: Premature stop (nonsense, frameshift, or splicing) mutations of COL2A1 usually result in STL1, whereas glycine substitutions in the triple-helix region are typically associated with lethal (such as achondrogenesis type 2/hypochondrogenesis) or more severe short stature (such as spondyloepiphyseal dysplasia congenital, Kniest dysplasia).