Clinical features vary widely not only between types, but within types, and even within the same family. Bones predisposed to fracture. Normal or near-normal stature. Brittle teeth possible. Hearing loss possible, beginning in early 20s or 30s.
Most fractures occur before puberty.
Type II Most severe form. Frequently lethal at or shortly after birth. Numerous fractures and severe bone deformity. Small stature with underdeveloped lungs. Type III Bones fracture easily.