Osteogenesis imperfecta refers to a group of several genetic disorders that manifest in bone abnormalities. Persons suffering from this condition break their bones very easily usually after mild trauma or even in absence of any apparent cause. They frequently suffer from multiple fractures. Estimates indicate that 6 to 7 in every 100,000 people are affected. The distribution is almost uniform worldwide.
There are about eight types of this condition that have been identified. These are types I to VII. They have many features in common. Only minute differences in signs and symptoms are used to distinguish them. Generally, type I is associated with the least severe signs and symptoms while type II is the most severe of them all. The others lie somewhere in the middle. There is on-going research to identify the genetic basis for the difference in the types.
In type I and all the other milder forms, bone fractures start in childhood and adolescence. In most cases there is preceding minor trauma. As the children grow into adulthood, the incidence of fractures is significantly reduced. The affected persons have a blue-grey tint on their sclera and often develop hearing loss later in adulthood. The height is usually normal in most cases.
Severe forms of the condition present with a high frequency of fractures. This typically starts way before the child is born. They suffer from numerous fractures that are not associated with any trauma. Additional features include hearing problems, abnormal teeth, blue sclera, short stature and respiratory problems. Respiratory problems are due to the presence of very fragile ribs as well as underdeveloped lungs.
Many studies have been done to identify the aetiological factors. IT has been established that a number of genes are responsible. These include COL1A1, CRTAP, LEPRE1 and COL1A2. Close to 90% of the cases result from mutations affecting COL1A1 and COL1A2 genes. These genes code for the synthesis of proteins that make up collagen type 1, an important component of bone, skin and several other connective tissues.
The abnormal genes are inherited through an autosomal dominance pattern. What this means is that as long as one of the copies of genes that code for the collagen synthesis is mutated, the condition will manifest. This is what happens as regards the inheritance of types I and IV. Type II and three usually have no predisposing positive family history; they are just sporadic mutations.
Currently there is no effective treatment for this disorder. The modes of management that are available aim at increasing bone strength and prevention of fractures. A drug known as alendronate has been tried in experimental cases but the results have been inconclusive. Conservative approaches include regular physical exercises, increased dietary calcium and vitamin D and prompt treatment of bone infections.
There several other options that can be considered in the management of osteogenesis imperfecta. These include surgery, physical aids and physiotherapy. Surgery helps to correct spinal defects such as scoliosis. Physiotherapy is done to improve the strength of bone and as a result to reduce fracture incidence. The physical aids used by the affected persons include wheelchairs, grabbing arms, splints and crutches.
There are about eight types of this condition that have been identified. These are types I to VII. They have many features in common. Only minute differences in signs and symptoms are used to distinguish them. Generally, type I is associated with the least severe signs and symptoms while type II is the most severe of them all. The others lie somewhere in the middle. There is on-going research to identify the genetic basis for the difference in the types.
In type I and all the other milder forms, bone fractures start in childhood and adolescence. In most cases there is preceding minor trauma. As the children grow into adulthood, the incidence of fractures is significantly reduced. The affected persons have a blue-grey tint on their sclera and often develop hearing loss later in adulthood. The height is usually normal in most cases.
Severe forms of the condition present with a high frequency of fractures. This typically starts way before the child is born. They suffer from numerous fractures that are not associated with any trauma. Additional features include hearing problems, abnormal teeth, blue sclera, short stature and respiratory problems. Respiratory problems are due to the presence of very fragile ribs as well as underdeveloped lungs.
Many studies have been done to identify the aetiological factors. IT has been established that a number of genes are responsible. These include COL1A1, CRTAP, LEPRE1 and COL1A2. Close to 90% of the cases result from mutations affecting COL1A1 and COL1A2 genes. These genes code for the synthesis of proteins that make up collagen type 1, an important component of bone, skin and several other connective tissues.
The abnormal genes are inherited through an autosomal dominance pattern. What this means is that as long as one of the copies of genes that code for the collagen synthesis is mutated, the condition will manifest. This is what happens as regards the inheritance of types I and IV. Type II and three usually have no predisposing positive family history; they are just sporadic mutations.
Currently there is no effective treatment for this disorder. The modes of management that are available aim at increasing bone strength and prevention of fractures. A drug known as alendronate has been tried in experimental cases but the results have been inconclusive. Conservative approaches include regular physical exercises, increased dietary calcium and vitamin D and prompt treatment of bone infections.
There several other options that can be considered in the management of osteogenesis imperfecta. These include surgery, physical aids and physiotherapy. Surgery helps to correct spinal defects such as scoliosis. Physiotherapy is done to improve the strength of bone and as a result to reduce fracture incidence. The physical aids used by the affected persons include wheelchairs, grabbing arms, splints and crutches.
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