Osteogenesis Imperfecta (OI) is a group of genetic disorders that mainly affect the bones. The term “osteogenesis
imperfecta” means imperfect bone formation. People with this condition have bones
that break easily, often from mild trauma or with no apparent cause. Multiple fractures
are common, and in severe cases, can occur even before birth. Milder cases may involve
only a few fractures over a person's lifetime.
There are at least eight recognized forms of osteogenesis imperfecta, designated type
I through type VIII. The types can be distinguished by their signs and symptoms, although
their characteristic features overlap. Type I is the mildest form of osteogenesis
imperfecta and type II is the most severe; other types of this condition have signs
and symptoms that fall somewhere between these two extremes. Increasingly, genetic
factors are used to define the different forms of osteogenesis imperfecta.
The milder forms of osteogenesis imperfecta, including type I, are characterized by
bone fractures during childhood and adolescence that often result from minor trauma.
Fractures occur less frequently in adulthood. People with mild forms of the condition
typically have a blue or grey tint to the part of the eye that is usually white (the
sclera), and may develop hearing loss in adulthood.
Other types of osteogenesis imperfecta are more severe, causing frequent bone fractures
that may begin before birth and result from little or no trauma. Additional features
of these conditions can include blue sclerae, short stature, hearing loss, respiratory
problems, and a disorder of tooth development called dentinogenesis imperfecta. The
most severe forms of osteogenesis imperfecta, particularly type II, can include an
abnormally small, fragile rib cage and underdeveloped lungs. Infants with these abnormalities
have life-threatening problems with breathing and often die shortly after birth.
DIAGNOSTIC TESTING AND CODING
Ultrasound can often detect severe cases of OI during pregnancy. The severe form of
OI Type II can be seen on ultrasound when the fetus is as young as 16 weeks. Genetic
testing may be able to identify the mutation. Most infants with more severe forms
of osteogenesis imperfecta (such as type II) have no history of the condition in their
family. In these infants, the condition is caused by new (sporadic) mutations in the
COL1A1 or COL1A2 gene.