Etiology: Autosomal dominant mutation in COL1A1 or COL1A2 genes; decreased formation of hydrogen and disulfide bonds between type 1 preprocollagen molecules → decreased triple helix formation → defective type I collagen synthesis → impaired bone matrix formation (osteogenesis)

Clinical features:- Growth retardation- Skeletal deformities, brittle bones, and recurrent fractures from minimal trauma- Blue sclerae- Progressive hearing loss- Brittle, opalescent teeth- Type II: most severe form; lethal perinatally or within the first year

Therapy- No cure available- IV bisphosphonates to increase cortical thickness- Surgery for functional improvement