COL2A1 and achondrogenesis type II: Mutations in COL2A1 cause a wide spectrum of skeletal disorders in humans including achondrogenesis type II (ACG2) (OMIM 200610, achondrogenesis, type II; ACG2) [8, 9] which is characterized by short limbs, short ribs, and absence or abnormal ossification of some skeletal parts [10, 11].