Osteogenesis Imperfecta

Osteogenesis imperfecta (OI), also known as brittle bone disease or Lobstein syndrome, is a common heritable disorder of collagen synthesis that results in defective, weak bony matrix, leading to bone fragility with fractures and deformity. A wide range of clinical manifestations may be seen, ranging from perinatal death to premature osteoporosis presenting in middle-aged adults. Important secondary clinical features are growth impairment resulting in a rhizomelic dwarfism, hearing loss, blue sclerae, dentinogenesis imperfecta, cardiopulmonary complications, and neurologic compromise due to basilar invagination. The radiologic findings play a key role in diagnosing the condition. The multiple fractures encountered in OI often raise suspicion of nonaccidental injury, and, therefore, radiologists must have an understanding of the clinical manifestations of OI, the range of its genetic variability, and its imaging findings. Type I OI is the most common form of disease, comprising up to 60% of people with OI. It is generally associated with the best prognosis. This condition is transmitted as an autosomal dominant trait, although new mutations may occur. The most frequent genetic mutation causing type I OI results in a decreased production of normal collagen. Many imaging features of type I OI are shared with other types, particularly type IV. The radiographic hallmark is osteopenia, which is manifest by decreased bone density and cortical thinning, particularly of the metaphyses. “Feathering” and coarsening of trabeculae may also be seen (Bauze RJ, Smith R, Francis MJ, J Bone Joint Surg Br 57:2–12, 1975). Harris growth-arrest lines are often present, corresponding to transient periods of epiphyseal disturbance and growth arrest. Apart from osteopenia, bowing and healing fractures may be evident. The long bones may appear overtubulated and gracile. In mild forms of OI, radiographs of the skull may be normal. With more severe forms, the skull demonstrates poor mineralization and multiple wormian, or intrasutural, bones (Cremin B, Goodman H, Spranger J, Beighton P, Skeletal Radiol 8:35–8, 1982). Wormian bones are considered significant when there are more than 10 in number, they measure greater than 6 by 4 mm, and are arranged in a general mosaic pattern.