Patients with dominant negative mutations in COL1A2 are linked to osteogenesis imperfecta types I–IV, Ehlers-Danlos syndrome type VIIB, recessive Ehlers-Danlos syndrome classical type, idiopathic osteoporosis, and atypical Marfan syndrome (33), whereas haploinsufficiency of COL1A2 leads to milder phenotypes. This evidence concerns the gene COL1A2 and Marfan syndrome.