Brittle bone disease is a disorder that results in fragile bones that break easily. It’s typically present at birth, but it only develops in children who have a family history of the disease.
The disease is often referred to as osteogenesis imperfecta (OI), which means “imperfectly formed bone.”
Brittle bone disease can range from mild to severe. Most cases are mild, resulting in few bone fractures. However, the severe forms of the disease can cause:
- hearing loss
- heart failure
- spinal cord problems
- permanent deformities
OI can sometimes be life-threatening if it occurs in babies either before or shortly after birth. Approximately one person in 20,000 will develop brittle bone disease. It occurs equally among males and females and among ethnic groups.
Brittle bone disease is caused by a defect, or flaw, in the gene that produces type 1 collagen, a protein used to create bone. The defective gene is usually inherited. In some cases, however, a genetic mutation, or change, can cause it.
Four different genes are responsible for collagen production. Some or all of these genes can be affected in people with OI. Defective genes can produce eight types of brittle bone disease, labeled as type 1 OI through type 8 OI. The first four types are the most common. The last four are extremely rare, and most are subtypes of type 4 OI. Here are the four main types of OI:
Type 1 OI
Type 1 OI is the mildest and most common form of brittle bone disease. In this type of brittle bone disease, your body produces quality collagen but not enough of it. This results in mildly fragile bones. Children with type 1 OI typically have bone fractures due to mild traumas. Such bone fractures are much less common in adults. The teeth may also be affected, resulting in dental cracks and cavities.
Type 2 OI
Type 2 OI is the most severe form of brittle bone disease, and it can be life-threatening. In type 2 OI, your body either doesn’t produce enough collagen or produces collagen that’s poor quality. Type 2 OI can cause bone deformities. If your child is born with type 2 OI, they may have a narrowed chest, broken or misshapen ribs, or underdeveloped lungs. Babies with type 2 OI can die in the womb or shortly after birth.
Type 3 OI
Type 3 OI is also a severe form of brittle bone disease. It causes bones to break easily. In type 3 OI, your child’s body produces enough collagen but it’s poor quality. Your child’s bones can even begin to break before birth. Bone deformities are common and may get worse as your child gets older.
Type 4 OI
Type 4 OI is the most variable form of brittle bone disease because its symptoms range from mild to severe. As with type 3 OI, your body produces enough collagen but the quality is poor. Children with type 4 OI are typically born with bowed legs, although the bowing tends to lessen with age.
The symptoms of brittle bone disease differ according to the type of the disease. Everyone with brittle bone disease has fragile bones, but the severity varies from person to person. Brittle bone disease has one or more of the following symptoms:
- bone deformities
- multiple broken bones
- loose joints
- weak teeth
- blue sclera, or a bluish color in the white of the eye
- bowed legs and arms
- kyphosis, or an abnormal outward curve of the upper spine
- scoliosis, or an abnormal lateral curve of the spine
- early hearing loss
- respiratory problems
- heart defects
Your doctor can diagnose brittle bone disease by taking X-rays. X-rays allow your doctor to see current and past broken bones. They also make it easier to view defects in the bones. Lab tests may be used to analyze the structure of your child’s collagen. In some cases, your doctor may want to do a skin punch biopsy. During this biopsy, the doctor will use a sharp, hollow tube to remove a small sample of your tissue.
Genetic testing can be done to trace the source of any defective genes.
There’s no cure for brittle bone disease. However, there are supportive therapies that help reduce your child’s risk of broken bones and increase their quality of life. Treatments for brittle bone disease include:
- physical and occupational therapy to increase your child’s mobility and muscle strength
- bisphosphonate medications to strengthen your child’s bones
- medicine to reduce any pain
- low-impact exercise to help build bone
- surgery to place rods in your child’s bones
- reconstructive surgery to correct bone deformities
- mental health counseling to help treat issues with body image
The long-term outlook varies depending on the type of brittle bone disease. Outlooks for the four main types of brittle bone disease are:
Type 1 OI
If your child has type 1 OI, they can live a normal life with relatively few problems.
Type 2 OI
Type 2 OI is often fatal. A child with type 2 OI may die in the womb or shortly after birth from respiratory problems.
Type 3 OI
If your child has type 3 OI, they may have severe bone deformities and often require a wheelchair to get around. They usually have shorter lifespans than people with type 1 or 4 OI.
Type 4 OI
If your child has type 4 OI, they may need crutches to walk. However, their life expectancy is normal or close to normal.