Classification of osteogenesis imperfecta into the four most frequent types∗.
|Type IA||Mild absence of bone deformity|
Caused by mutations in COL1A1 or COL1A2
Affects approximately 60–70% of carriers of OI
|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|
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. .|
**Additional subtypes: I-A and I-B (Levin et al. ); III-A and III-B (adopted in the present study); IV-A and IV-B (Paterson et al. ).
Footnote. OI may also be classified into types V (Glorieux et al. ), VI (Glorieux et al. ), VII (Ward et al. ), and VIII (Cabral et al. ) based on clinical and bone histological parameters.