Brittle Bone diseases

Also known as: Osteogenesis Imperfecta

Background

Brittle bone disease or osteogenesis imperfecta (OI) is a genetic condition that causes abnormality in collagen protein that the body needs for bones as well as other structures such as skin, ligaments and teeth. Seven forms of OI have been described. They include mild, moderate and severe forms.

Credits

Medical text written November 2002 by Professor SF Ahmed. Last updated December 2012 by Professor SF Ahmed, Consultant in Paediatric Endocrinology and Bone Metabolism, Royal Hospital For Sick Children, Yorkhill, Glasgow, UK.

What are the symptoms?

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 (deafness).

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.

What are the causes?

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 it 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.

How is it treated?

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.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
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.

Is there support?

Brittle Bone Society

Tel: 01382 204 446
Email: admin@brittlebone.org
Website: brittlebone.org

The Society is a Registered Charity in England and Wales No. 272100 and Scotland No. SC010951. It provides information and support to people affected by the bone condition Osteogenesis Imperfecta in the UK and Republic of Ireland.

Group details last updated December 2020.

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