A rare connective tissue disorder characterized by fragile bones. Type VII is a severe form of the condition which is recessively inherited.
* Osteopenia * Short arm bone * Short thigh bone * Short stature * Fractures at birth
Osteogenesis imperfecta can result from autosomal dominant inheritance of a defect in the amount of Type I collagen, an important part of the bone matrix. Clinical signs may result from defective osteoblastic activity and a defect of mesenchymal collagen (embryonic connective tissue) and its derivatives (sclerae, bones, and ligaments). The reticulum fails to differentiate into mature collagen or causes abnormal collagen development, leading to immature and coarse bone formation. Cortical bone thinning also occurs. Type I, the most common form of osteogenesis imperfecta, occurs in about 1 in 30,000 live births. Both types I and IV are thought to be inherited as an autosomal dominant trait. Types II and III are believed to be inherited as an autosomal recessive trait.
Family history and characteristic features, such as blue sclerae or deafness, establish the diagnosis. Whenever possible, collagen biochemical studies of cultured skin fibroblasts should be performed. Prenatal diagnosis may be available for certain families with an identified mutation. Prenatal ultrasound performed as early as 16 weeks may show evidence of severe osteogenesis imperfecta. X-rays showing evidence of multiple old fractures and skeletal deformities and a skull X-ray showing wide sutures with small, irregularly shaped islands of bone (wormian bones) between them support the diagnosis. These findings can help differentiate osteogenesis imperfecta from child abuse or from other disorders such as juvenile idiopathic osteoporosis. In a family with a history of type II osteogenesis imperfecta, diagnostic serial ultrasound should be considered for future pregnancies to detect limb shortening, in utero fractures, and polyhydramnios.
Treatment aims to prevent deformities by traction, immobilization, or both and to aid normal development and rehabilitation. Fractures must be repaired quickly to avoid deformities. Surgical procedures such as inserting metal rods through bones can help strengthen bones and prevent deformity. The use of bisphosphonates in children with osteogenesis imperfecta is being researched, as are growth hormone and gene therapies. Other medical interventions include bone marrow transplant. Supportive measures include: ❑ checking the patient's circulatory, motor, and sensory abilities ❑ encouraging the patient to walk when possible (children with osteogenesis imperfecta develop a fear of walking) ❑ teaching preventive measures, such as avoiding contact sports or strenuous activities or wearing knee pads, helmets, or other protective devices when engaging in sports ❑ assessing for and treating scoliosis, a common complication ❑ promoting preventive dental care and repair of dental caries.