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 
The first four types are the most common. The last four are extremely rare, and most are subtypes of type 4 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 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 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 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 first sign that a baby or toddler may have OI is frequently broken bones that appear without any stress. Broken bones are frequently present at birth in infants with moderate or severe forms of OI. When performing routine tasks like changing diapers, being raised, being burped, or when they first start standing and walking, kids with milder OI (Type I) frequently break their first bone. Some extremely mild OI Type I instances don’t get diagnosed until adolescence or adulthood.

The symptoms of brittle bone disease differ according from one person to another pending on the type of the disease. Everyone with brittle bone disease does have 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 colour 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

OI is still mostly diagnosed by clinical means. Based on the existence of fractures and other clinical signs, a doctor, typically a geneticist, can frequently make the diagnosis. A genetic examination can validate the diagnosis. To distinguish the injury from those brought on by physical child abuse, this is very crucial. To exclude conditions like Hypophosphatasia or rickets, further blood and urine tests are frequently performed. Prenatal testing is available for the more severe cases of OI.

Your doctor can diagnose brittle bone disease by taking X-rays. X-rays, this allows 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 analyse 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 counselling 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.
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.
It is said there OI is now up to type 20. There can be a combination of symptoms of different type in one individual.