People with OI type I have an average of 20 to 40 fractures before puberty. Fewer fractures occur after puberty. Prenatal diagnosis often is possible. OI type II results from a new mutation. Infants with this form of OI have fractures before birth, have extremely fragile bones, and usually die shortly after birth.
Prenatal diagnosis is possible.
It usually results from a new dominant mutation. These people often have many spontaneous fractures. It is not unusual for a person to have 20 or more fractures occurring during the first three years of life and more than 100 fractures by puberty. Loose joints and poor muscle development are common. Prenatal diagnosis often is possible.