Osteogenesis imperfecta

Brittle bone disease. Osteogenesis imperfecta (OI) is not one but a group of genetic diseases, all of which affect collagen in connective tissue in the body and all of which result in fragile bones. The best known types are types I and II.

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osteogenesis im·per·fec·ta -.im-pər-'fek-tə n a hereditary disease caused by defective or deficient collagen production and marked by extreme brittleness of the long bones and a bluish color of the whites of the eyes called also fragilitas ossium, osteopsathyrosis

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a congenital disorder in which the bones are unusually brittle and fragile. It has an incidence of 1 in 20, 000. No treatment is available, but the tendency to fracture sometimes diminishes at adolescence. There are four types, of varying severity, the worst being lethal at birth. The sclerae may be blue, and the teeth can be deformed.

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(OI) a group of inherited connective tissue disorders characterized by brittle, easily fractured bones and sometimes other manifestations, including blue sclerae, wormian bones, shortened limbs and limb deformities, fragile skin, muscle weakness, lax joints, bleeding and easy bruising, hearing loss, dyspnea, and dentinogenesis imperfecta. It is subdivided into eight types, I–VIII, on the basis of clinical features, course, and radiographic findings, but phenotypes vary greatly within types. Most cases are caused by autosomal dominant mutations in COL1A1 or COL1A2, genes that encode the a1 chain of type I collagen; the mutations may result in production of abnormal collagen or in decreased production of normal collagen. There are several rarer types caused by autosomal recessive mutations of the cartilage-associated protein (CRTAP) or prolyl 3-hydroxylase 1 (LEPRE1) genes, both of which are involved in processing of the a1 chain of type I collagen. Type I, the most common, is also the mildest, and accounts for approximately 50 per cent of cases. Type II is the most severe, and is usually lethal in infancy.

Osteogenesis imperfecta type II. The infant was born with multiple fractures and limb deformities and had dark bluish-gray sclerae.