Osteogenesis imperfecta

Inheritance

How is osteogenesis imperfecta inherited?

Most people with osteogenesis imperfecta (OI) have an altered COL1A1 or COL1A2 gene, which are inherited in an autosomal dominant manner. This is one way a disorder or trait can be passed down through a family. The first word, "autosomal," means on a chromosome that both males and females carry. Therefore, OI can affect either gender. The second word, "dominant," means a change in one copy of a person's COL1A1 or COL1A2 gene is enough for them to develop OI. We have two copies of every gene - one from our mother and one from our father - for a dominant condition, only one of them needs to have the problem. This means that if a parent carries altered form of one of these genes, they have a 50% chance to pass the affected gene to each of their offspring, regardless of gender. This also means that there is a 50% chance that an affected parent would not pass this on to their children. Genetic testing may be available to determine if a child has inherited the altered gene.

Some people, especially those with the severe forms of OI, may be the first person in the family with the disorder. This occurs because of a de novo mutation, which means that the altered gene occurs randomly, most likely after fertilization. The child who carries the altered gene can pass on the alteration in an autosomal dominant manner. In families with a child with a de novo mutation, the likelihood of having another child with OI is extremely low.

Less often, people with OI have autosomal recessive inheritance. Everyone has two copies of the autosomal genes; one received from their father and one from their mother. Autosomal recessive inheritance means that a person receives a nonworking copy of a specific gene from both parents. The parents have one working copy of the gene and one nonworking copy; they are carriers for autosomal recessive OI. Carriers do not develop symptoms of the disorder. If two people who are carriers for autosomal recessive OI, there is a 25% chance with each pregnancy that the child will have the disorder and a 50% chance the child will also be a carrier.

If you have a family member with OI and you would like to know if you are a carrier, talk to your doctor or meet with a genetic counselor to discuss testing options.

SOURCE: Emory University - Department of Human Genetics in collaboration with ThinkGenetic • https://www.thinkgenetic.com/diseases/osteogenesis-imperfecta/inheritance/27305 • DATE UPDATED: 2017-04-10

References

Osteogenesis Imperfecta. The Genetics Home Reference website. Accessed April 6, 2017. https://ghr.nlm.nih.gov/condition/osteogenesis-imperfecta

Osteogenesis Imperfecta. The National Organization for Rare Disorders website. Accessed April 6, 2017. https://rarediseases.org/rare-diseases/osteogenesis-imperfecta/

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