When the bone formation is less than perfect
Osteogenesis imperfecta is a serious disease of the bone with no known cause. As the name indicates, the disease affects the bones during their formation in vivo and renders them brittle. This condition occurs in two forms—one is present at birth and the other manifests later in childhood. Almost all infants with the former type of Osteogenesis imperfecta are stillborn or die shortly after birth.