OI is a genetic disease. A number of genetic defects cause the abnormal type I collagen synthesis that leads to OI. OI generally arises from mutations in 1 of 2 genes that encode for the synthesis and/or structure of type I collagen.

The inheritance pattern is usually autosomal dominant. This means an affected person will have OI even though only one faulty gene has been passed along. This faulty gene can come from either parent, and it can affect either sex. Each child of an affected parent will have a 50 percent chance of developing OI.

Occasionally, a person will develop OI even though neither parent carried the faulty gene. This is called a spontaneous mutation. A person who develops OI will have the same chance of passing it on to a child as does someone who inherited the autosomal dominant gene.

Milder forms of OI are caused primarily by a decrease in production of normal collagen, whereas more severe forms are caused primarily by the production of abnormal collagen. These abnormalities may be dominantly inherited, or they may be the result of sporadic mutation.

Genetic Counselling ....
It is important for you to understand that nothing you or your spouse did during conception or pregnancy caused this condition in your child. OI has been prevalent for thousands of years. Genetic counselling, which is available at most hospitals, may help you understand the type of OI your child has.

Parents of a child with Osteogenesis Imperfecta should receive genetic counselling if they wish to have more children. You should consider contacting a geneticist who can help determine the probability of recurrence of OI in your family. Types I through III of the disorder are inherited in an autosomal dominant pattern, meaning only one defective gene needs to be inherited for Osteogenesis Imperfecta to appear. Therefore, each future child has a 50% chance of being born with the disorder.