Osteogenesis imperfecta is a condition causing extremely fragile bones.

Osteogenesis imperfecta (OI) is a congenital disease, meaning it is present at birth. It is frequently caused by defect in the gene that produces type 1 collagen, an important building block of bone. There are many different defects that can affect this gene. The severity of OI depends on the specific gene defect.

OI is an autosomal dominant disease. That means if you have one copy of the gene, you will have the disease. Most cases of OI are inherited from a parent, although some cases are the result of new genetic mutations.

A person with OI has a 50% chance of passing on the gene and the disease to their children.

All people with OI have weak bones, which makes them susceptible to fractures. Persons with OI are usually below average height ( short stature). However, the severity of the disease varies greatly.

The classic symptoms include:

• Blue tint to the whites of their eyes (blue sclera)
• Multiple bone fractures
• Early hearing loss (deafness)

Because type I collagen is also found in ligaments, persons with OI often have loose joints (hypermobility) and flat feet. Some types of OI also lead to the development of poor teeth.

Symptoms of more severe forms of OI may include:

• Bowed legs and arms
• Kyphosis (S-curve spine)
• Scoliosis

OI is usually suspected in children whose bones break with very little force. A physical examination may show that the whites of their eyes have a blue tint.

A definitive diagnosis may be made using a skin punch biopsy. Family members may be given a DNA blood test.

If there is a family history of OI, chorionic villus sampling may be done during pregnancy to determine if the baby has the condition. However, because so many different mutations can cause OI, some forms cannot be diagnosed with a genetic test.

The severe form of type II osteogenesis imperfecta can be seen on ultrasound when the fetus is as young as 16 weeks.