The disease osteogenesis imperfecta (OI), more commonly known as brittle bone disease,
is a congenital disease causing bone fractures in children and adults.
Osteogenesis Imperfecta (OI) is a genetic condition characterised by bones that break easily, often from little or no apparent cause. The condition can vary quite drastically from person to person so a classification system has been identified to describe the different types of OI which is commonly used to help describe how severely a person with OI is affected. For example, a person may have just a few or as many as several hundred fractures in a lifetime.
Case studies of fragile bones and hearing loss have appeared in the medical literature since the 1600s.The term “osteogenesis imperfecta” was originated by W. Vrolik in 1849, and the condition was loosely divided into “congenita” and “tarda” by E. Looser in 1906. Van der Hoeve in 1918 described the occurrence of fragile bones, in combination with blue sclera and early deafness as a distinct inherited syndrome.
Brittle Bone Disease - Books
Barnaby and His Brittle Bones
The Unbreakable Boy
A Little More Than Perfect: My Life with (and in Spite Of) Osteogenesis Imperfecta
The Symptoms of brittle bone disease:
All people with OI have weak bones, which makes them susceptible to fractures. People 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 the eyes (blue sclera)
- multiple bone fractures - the frequency of fractures may increase in adolescence
- early hearing loss
- bone deformities
- multiple broken bones
- loose joints
- short stature
- weak teeth
- triangular-shaped face
- early hearing loss
- respiratory problems
- heart defects
Because collagen is also found in ligaments, people 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 (over-curvature of the upper back)
- scoliosis (an abnormal lateral curve of the spine)
The Causes of brittle bone disease
OI is a genetic disorder. Most cases (90 percent) involve a change (mutation) in type 1 collagen - the protein 'scaffolding' of bone and other connective tissues. Other cases of OI are caused by changes in other genes in bone development.
How is the disease diagnosed
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 on the basis of examination of the person, examining the skeleton by X-rays, excluding other causes of bone fragility and sometimes by genetic tests.
Types of Brittle Bone Disease
There are four different genes responsible for collagen production, and any combination, or all, of them can be affected. These combinations 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 types are extremely rare and most are subtypes of type 4 OI. Details for each type include:
Type 1 OI is the mildest and most common form of brittle bone disease your baby can have. With this type, your child’s body produces normal quality collagen, but just not enough of it. This results in only mildly fragile bones. Children with type 1 OI typically experience 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
Type 2 OI, the most severe form of brittle bone disease, is fatal. In type 2 OI, your child’s body either produces poor-quality collagen or not enough of it. Type 2 OI can produce bone deformities. Infants born with type 2 OI may have narrowed chests, broken or misshapen ribs, and underdeveloped lungs. Babies with type 2 OI die either in the womb or shortly after birth.
Type 3 OI is a severe form of brittle bone disease that also causes bones to break easily. In Type 3 OI, your child’s body produces enough collagen, but it is of poor quality. A baby’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, the body produces enough collagen, but the quality is poor. Infants with type 4 OI are typically born with bowed legs, although the bowing tends to lessen with age.
Treatment for the disease
Fractures need to be treated, but the immobilisation period should be kept to a minimum as activity allows muscles and bones to stay as strong as possible. It is important for someone with OI to have a well-balanced diet with adequate calcium.
There is no specific drug therapy for OI, but it has been shown that a group of drugs called bisphosphonates can reduce bone loss, the number of fractures and the chronic pain experienced by these children. Most children obtain maximum benefit from this drug over the first two years of treatment.
Some children may benefit from insertion of rods to support the bones. Regular monitoring of other functions such as hearing is required.
Although there is no cure for brittle bone disease, there are supportive therapies that help reduce the risk of broken bones and increase quality of life. Treatments for brittle bone disease include:
- physical and occupational therapy to increase your child’s mobility and muscle strength to help reduce risk of fractures
- medication to reduce any pain
- low-impact exercise to help build bone
- reconstructive surgery to correct bone deformities
- mental-health counseling to help with body-image issues
Managing brittle bone disease
- Techniques for safe handling, protective positioning and safe movement are taught to parents
- Infancy, early childhood and the pre-teen years are often challenging
- Growth and hormonal changes can affect the frequency of fractures
- Children and youth learn which activities to avoid and how to practice energy conservation
- The number of fractures usually decreases in adulthood
- Following a healthy lifestyle including not smoking, and maintaining a healthy weight is beneficial
Inheritance patterns and prenatal diagnosis
Type I and IV are usually inherited in an autosomal dominant manner but new mutations in a family (sporadic) often occur. Affected families should be referred to a genetics centre for information and support. Prenatal diagnosis Severe cases may be detected by ultrasound scanning. A DNA test may be available at eight weeks for some affected families where the genetic mutation is already known.
Your prognosis varies depending on the type of brittle bone disease. Outlooks for the four main types of brittle bone disease are:Type 1
People with type 1 OI can live a normal lifespan with relatively few problems.Type 2
Type 2 OI is fatal. Infants with type 2 OI may die in the womb, or shortly after birth from respiratory problems.Type 3
Children with type 3 OI may have severe bone deformities and often require a wheelchair to get around. People with type 3 OI usually have shorter lifespans than anyone with type 1 or 4 OI.Type 4
Children with type 4 OI may need crutches to walk. The lifespan of people with type 4 OI is normal or close to normal.
Sources of Help
Osteogenesis imperfecta - Wikipedia - https://en.wikipedia.org/wiki/Osteogenesis_imperfecta
Healthline - Brittle Bone Disease (Osteogenesis Imperfecta) - https://www.healthline.com/health/osteogenesis-imperfecta#Overview1