An Overview of Osteogenesis Imperfecta Genetics
With rare exceptions,
osteogenesis imperfecta (OI) typically results from mutations in the type I collagen genes and is considered to be a dominantly inherited disorder. On the basis of a limited number of population surveys, the overall frequency of OI in the general population is about 1 in 20,000.
Because some infants die at birth and would not be included in these surveys, the birth incidence is slightly higher, perhaps 1 in 15,000 to 18,000 births. In families in which OI occurs in more than one generation with clearly dominant inheritance, the risk of recurrence of OI is 50 percent for each pregnancy.
How Did My Child Get Osteogenesis Imperfecta?
When parents who have no
osteogenesis imperfecta symptoms have a child with OI, they will inquire about how this occurred in their family and about the risk of recurrence. For the great majority of these families (about 90 percent), their child's OI was caused by a new mutation that took place in the egg or sperm near the time of conception. Their risk of recurrence in subsequent pregnancies is approximately equal to the risk of osteogenesis imperfecta in the general population.
In the remainder of these families (about 10 percent), the child's osteogenesis imperfecta results from mosaicism for the mutation in one parent. A mosaic parent has the mutation in some of the cells of his or her body, including some of the egg or sperm cells. The mosaic parent usually appears to be unaffected or only mildly affected. Parental mosaicism can be determined by genetic testing. For these parents, the risk of subsequent affected children is between 10 and 50 percent per pregnancy.
There are very unusual forms of OI that seem to be inherited in a recessive fashion, which means that each parent is a carrier and contributes one altered gene each to their child, who is then affected with osteogenesis imperfecta.
Add this article to your Favorites
Email this article
Print