Osteogenesis imperfecta is the best known disorder of a group of disorders that disturb bone growth. These disorders are called osteodysplasias. In osteogenesis imperfecta, synthesis of collagen, one of the normal components of bone, is impaired. The bones become weak and break (fracture) easily. There are 4 main types of osteogenesis imperfecta.
Osteogenesis imperfecta can range from mild to severe. Most people with osteogenesis imperfecta have fragile bones, and about 50 to 65% have hearing loss. Osteogenesis imperfecta causes the whites of the eyes (sclerae) in some people to turn blue. The blue color appears because the veins beneath the abnormally thin sclerae show through. The sclerae are thinner than normal because collagen has not been formed correctly. Children may have discolored and poorly developed teeth (called dentinogenesis imperfecta) depending on the type of osteogenesis imperfecta. Sometimes heart or lung diseases develop in children with osteogenesis imperfecta.
Type I osteogenesis imperfecta is the mildest type. Some children may have only symptoms of blue sclerae and muscle and joint pain caused by loose joints. Children with this type may have increased risk of fractures during childhood.
Type II osteogenesis imperfecta is the most severe type and causes death. Infants are usually born with many broken bones. The skull may be so soft that the brain is not protected from pressure applied to the head during childbirth. These infants have shortened arms and legs and blue sclerae. Infants with this type can die before childbirth or within the first few days or weeks of life.
Type III osteogenesis imperfecta is the most severe type that does not cause death. Children with this type are very short and have curving of the spine and frequent fractures. This type causes bones to often break after very minor injuries, usually when children begin to walk. These children also have a large skull and a triangular face shape caused by overdevelopment of the head and underdevelopment of the face bones. Chest deformities are common. The color of the sclerae varies.
Type IV osteogenesis imperfecta is a moderate type. Children with this type have bones that fracture easily during childhood before puberty. The sclerae are typically white. Children are short. Children with this type may benefit from treatment.
Doctors base the diagnosis of osteogenesis imperfecta on the symptoms and on a physical examination.
If the diagnosis is not clear, doctors may remove a sample of skin for examination under a microscope (biopsy) to analyze a type of connective tissue cell (fibroblasts) or they may take a sample of blood to analyze certain genes.
The most severe and lethal form of osteogenesis imperfecta can be detected in pregnant women by an ultrasound.
X-rays may show abnormal bone structure that suggests osteogenesis imperfecta.
A test called audiometry is done often throughout childhood to monitor hearing.
Growth hormone injections can help children with types I and IV.
A type of drug called a bisphosphonate can help strengthen bones and lessen pain and the frequency of fractures. Bisphosphonates can be given by vein (pamidronate) or taken by mouth (alendronate).
Treatment of broken bones is similar to that for children who do not have the disorder. However, broken bones can become deformed or fail to grow. As a result, body growth can become permanently stunted in children with many broken bones, and deformities are common. Bones may require stabilization with internal metal rods. Physical therapy and occupational therapy help prevent fractures and improve function. Taking measures to avoid even minor injuries can help prevent fractures.
Some children may be helped by a cochlear implant (a device that converts sound waves to electrical signals that it sends to electrodes implanted in the inner ear).