Osteogenesis Imperfecta (OI) is a disorder in which there is either not enough collagen, or the collagen is formed abnormally. The disease can be very mild but can also be lethal. There are many different types of collagen in the body, and OI specifically is a disorder of Type I collagen. The most visible place in which type I collagen is located is in bone; however, type I collagen is also located in teeth, the whites of the eyes, ears, skin, ligaments, heart valves, and blood vessels. Therefore, even though OI is characteristically known as a bone disorder, the disease can affect other organ systems as well.

Consequences of OI

• Scoliosis
  Curving of the spine can occur because of a weakening in the bones. Fractures and loosening of the ligaments surrounding the spine can also occur.
  
  
• Skull abnormalities
  In more severe types of OI, the skull is weakened. As a result, these children (and adults) will sometimes have unusually large heads and their faces can be flattened and appear triangular.
  
  
• Short stature
  There is a direct relationship between the severity of OI and the amount that it restricts a person’s height.  Scoliosis of the spine can make the trunk shorter as the spine twists, curving of the bones and fractures of the growth areas of bone can severely restrict ultimate height.
  
  
• Dentinogenesis Imperfecta
  Type I collagen found in a person’s teeth is called Dentin. If the dentin becomes abnormal, teeth become weaker, and they are more prone to rapid wear, breakage and tooth loss.  Approximately 30% of all children with OI have significant dental issues.  Teeth may appear brown as the enamel has worn away.
  
  
• Blue Sclera
  A child’s eye can appear translucent because of a collagen deficiency in their cornea. As the eye becomes more translucent, it reveals underlying pigments and blood vessels; thus, the whites of the eyes actually appear blue.
  
  
• Hearing loss
  Small fractures of the ear bones can lead to hearing loss, and almost half of adults with OI have some type of hearing loss.
  
  
• Heart and Blood Vessel Problems
  OI can cause expansion of the aorta, brain blood vessels, and heart chambers. Consequently during surgery, children and adults with OI may have increased tendencies to bleed.

Causes

Osteogenesis Imperfecta is an inherited disorder, caused by a DNA mutation. Currently, there are over 300 known genetic mutations associated with OI, which is one of the reasons why some forms of OI are much more severe than others. However, approximately half of those who have OI have no family history, and so their DNA underwent a spontaneous mutation. Approximately 1 out of every 20,000 live births results in Osteogenesis Imperfecta.

Diagnosis

Classically, OI is described as having four main types (from the Sillence classification). A genetic test can often determine which type of OI your child has. Since the Sillence classification was described in 1979, there has been a multitude of new types of OI discovered. Nevertheless, the “classic” four types are as follows:

• Type 1: Mild OI

These children often have blue sclera, meaning that the whites of the eyes, rather than being white, are blue.  They are typically normal to short stature, and fractures typically do not occur until preschool when children are walking.  Their teeth may be affected as well (known as dentinogenesis imperfect).

• Type II: Lethal usually at birth

Unfortunately, the collagen is extremely abnormal with this type of OI.  The reason why this type is so dangerous is because the bone is so weak.  Fractures occur, often to the skull and ribs, while the baby is still in utero causing respiratory failure and/or stroke.

• Type III: Severe

These children typically have fractures when they are born.  The whites of the eyes may continue to stay white.  Their stature is extremely short, and their spine is often deformed.  While life expectancy is decreased, typically because of respiratory illness, with new advances, these children are living longer and longer.

• Type IV: Moderate to severe OI

These children are usually short in stature with teeth that are often affected. Fractures and crooked bones are quite common. A pediatric orthopaedic surgeon is often required to care for these patients as surgeries are likely required to protect the bone against future fractures and to straighten out crooked bones. Medications to make bones stronger, known as bisphosphonates, are typically prescribed

Treatment

From the perspective of the orthopaedic surgeon, the treatment of children with OI is focused on maximizing function and minimizing pain. Both of these goals are best accomplished by decreasing the number of fractures that a child with OI endures. Strategies used to improve bone health include:

• Encouragement of walking, as putting weight on bones actually improves its strength
• Use of braces, when necessary
• Exercise and/or physical therapy
• Taking adequate levels of daily calcium and vitamin D

Bisphosphonates, which improve bone density, can benefit those with more severe OI. This type of medication has revolutionized care for children with OI. It has allowed previously wheelchair-dependent kids to be able to walk. It has allowed children who previously were in chronic pain to live a life with less pain and less fractures. These medications are not without risk, and therefore, must be discussed in detail with your physician before starting such treatment. Lastly, your surgeon may recommend a procedure to straighten out the bones and insert rods to protect against future deformity and fracture. All of these options are discussed in detail during your office visits.

For more information about treatment recommendations for osteogenesis imperfecta, please visit the OI Foundation.