By Marjorie Vargas
Osteogenesis imperfecta is a disorder of bone that results from abnormalities in a group of genes that code for bone formation. The bones formed are weak and break very easily. Consequently, affected persons will frequently suffer multiple injuries following mild trauma or just spontaneously. It is estimated that close to 7 people are affected per 100,000 of population. The distribution is almost the same worldwide.
At least 8 types of the disorder have been profiled to date. These are type I through VII. The different types have many overlapping features and a few differences in terms of signs and symptoms. Type I is regarded as the least severe and type II is the most severe. The rest are somewhere in-between. Studies are going on to try and establish the reason as to why some people are affected by one type and not the other.
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.
In the severe forms, the frequency of fractures is much higher. The problem starts even before the child is born. They suffer multiple fractures while still in the uterus usually without any predisposing trauma. There are other accompanying features that include abnormal teeth, blue sclerae, short stature and respiratory problems. The respiratory problems are caused by fragile ribs and the presence of underdeveloped lungs.
A lot of studies have been carried out in this area. In terms of genetics the genes believed to be responsible for the abnormality include COL1A1, COL1A2, LEPRE1 and CRTAP. Mutations affecting the COL1A1 and COL1A2 alone are responsible for more than 90% of the cases. These genes code for proteins that are required for the synthesis of collagen type 1. This collagen is very important in the integrity of skin and bone as well as other connective tissues.
The type of inheritance pattern that is seen in this condition is what is known as autosomal dominant inheritance. In this kind of inheritance diseases are inherited when a copy of a gene in a pair is mutated as opposed to the autosomal recessive where both copies in the pair have to be mutated. This is the case with types IV and I. Types II and III come about as a result of sporadic gene mutations.
There is no definitive treatment for this disorder at present. The available modes of management are aimed at strengthening the bones so as to reduce the incidence of fractures. The drug alendronate, a bisphosphonate, has undergone several clinical trials to check for its effectiveness but the results are still inconclusive. Other conservative measures include engagement in weight bearing exercises regularly and increasing the intake of calcium and vitamin D. Bone infections should be treated promptly.
There are other options that may be considered in managing osteogenesis imperfecta. These include physiotherapy, surgery and the use of physical aids. Physiotherapy involves the stretching of muscles and joints regularly by a trained professional in a bid to increase the strength and reduce the chances of getting fractures. Surgery is done to insert metal rods in some long bones and to correct spine defects. The physical aids that can be used include crutches, grabbing arms, splints and wheelchairs.
At least 8 types of the disorder have been profiled to date. These are type I through VII. The different types have many overlapping features and a few differences in terms of signs and symptoms. Type I is regarded as the least severe and type II is the most severe. The rest are somewhere in-between. Studies are going on to try and establish the reason as to why some people are affected by one type and not the other.
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.
In the severe forms, the frequency of fractures is much higher. The problem starts even before the child is born. They suffer multiple fractures while still in the uterus usually without any predisposing trauma. There are other accompanying features that include abnormal teeth, blue sclerae, short stature and respiratory problems. The respiratory problems are caused by fragile ribs and the presence of underdeveloped lungs.
A lot of studies have been carried out in this area. In terms of genetics the genes believed to be responsible for the abnormality include COL1A1, COL1A2, LEPRE1 and CRTAP. Mutations affecting the COL1A1 and COL1A2 alone are responsible for more than 90% of the cases. These genes code for proteins that are required for the synthesis of collagen type 1. This collagen is very important in the integrity of skin and bone as well as other connective tissues.
The type of inheritance pattern that is seen in this condition is what is known as autosomal dominant inheritance. In this kind of inheritance diseases are inherited when a copy of a gene in a pair is mutated as opposed to the autosomal recessive where both copies in the pair have to be mutated. This is the case with types IV and I. Types II and III come about as a result of sporadic gene mutations.
There is no definitive treatment for this disorder at present. The available modes of management are aimed at strengthening the bones so as to reduce the incidence of fractures. The drug alendronate, a bisphosphonate, has undergone several clinical trials to check for its effectiveness but the results are still inconclusive. Other conservative measures include engagement in weight bearing exercises regularly and increasing the intake of calcium and vitamin D. Bone infections should be treated promptly.
There are other options that may be considered in managing osteogenesis imperfecta. These include physiotherapy, surgery and the use of physical aids. Physiotherapy involves the stretching of muscles and joints regularly by a trained professional in a bid to increase the strength and reduce the chances of getting fractures. Surgery is done to insert metal rods in some long bones and to correct spine defects. The physical aids that can be used include crutches, grabbing arms, splints and wheelchairs.
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