OI is caused by genetic defects that affect the body’s ability to make strong bones. In dominant (classical) OI, a person has too little type I collagen or a poor quality of type I collagen due to a mutation in one of the type I collagen genes. Collagen is the major protein of the body’s connective tissue. It is part of the framework that bones are formed around. In recessive OI, mutations in other genes interfere with collagen production. The result in all cases is fragile bones that break easily.

There is not yet a cure for OI. Treatment is directed toward preventing or controlling the symptoms, maximizing independent mobility, and developing optimal bone mass and muscle strength. Care of fractures, extensive surgical and dental procedures, and physical therapy are often recommended for people with OI. Use of wheelchairs, braces, and other mobility aids is common, particularly (although not exclusively) among people with more severe types of OI.

Despite numerous fractures, restricted physical activity, and short stature, most adults and children with OI lead productive and successful lives. They attend school, develop friendships and other relationships, have careers, raise families, participate in sports and other recreational activities and are active members of their communities.

The prognosis for a person with OI varies greatly depending on the number and severity of symptoms. Respiratory failure is the most frequent cause of death for people with OI, followed by accidental trauma.