Table 1.

Classification of osteogenesis imperfecta into the four most frequent types^∗.

Types∗∗	Main features
Type IA	Mild absence of bone deformity Caused by mutations in COL1A1 or COL1A2 Affects approximately 60–70% of carriers of OI Blue sclerae Normal stature
Type IB	Dentinogenesis imperfecta associated with type IA
Type II	More severe form High antenatal mortality rate due to extreme bone fragility
Type IIIA	Presence of progressive bone deformities and short stature Presence of extreme ligamentous laxity Affects approximately 20% of carriers of OI
Type IIIB	Dentinogenesis imperfecta associated with type IIIA
Type IVA	Mild deformities with variable degrees of short stature Diversified form Blue and white-grayish sclerae Associated hearing loss Mutations in COL1A1 or COL1A2 Affects approximately 10% of carriers of OI
Type IVB	Dentinogenesis imperfecta associated with type IVA

∗Modified from Sillence et al. [14].

∗∗Additional subtypes: I-A and I-B (Levin et al. [15]); III-A and III-B (adopted in the present study); IV-A and IV-B (Paterson et al. [16]).

Footnote. OI may also be classified into types V (Glorieux et al. [17]), VI (Glorieux et al. [18]), VII (Ward et al. [19]), and VIII (Cabral et al. [20]) based on clinical and bone histological parameters.