Osteopetrosis is a rare genetic disease which affects osteoclasts. These are cells which dissolve bone, so that it can be reshaped during growth or repaired after injury. This defect causes bones throughout the body to become excessively dense and to fracture easily. Nerves which sit in bony channels (such as those which pass through the skull to the eye or ear) can be damaged since these channels do not enlarge as the nerves grow.

Infantile ('malignant') Osteopetrosis is the most severe form of the disease. Affected children tend to be short but with relatively large heads. They often sustain birth fractures and may be jittery or or have convulsions during the first month of life due to a low blood calcium. Subsequently they develop persistent snuffles (narrow nasal passages) and are prone to infections. Bone marrow cavities are reduced: blood is then, established in the liver and spleen, causing swelling of these organs and a low blood count may result. Many children become blind by six months of age, deafness and hydrocephalus may develop later. A variety of different forms of the disease have been described, although the genetic cause is only known in approximately fifty per cent of affected children.

Without treatment many affected children die before adolescence. However, in those for whom suitable donors can be found, bone marrow transplantation may be curative. Alternatively, injections of gamma interferon may alleviate some symptoms of the disease.

Adult ('benign') Osteopetrosis tends to be diagnosed in late adolescence or early adulthood when bones are X-rayed due to a fracture. Some people may go on to develop bone pain, dental problems and deafness or facial nerve paralysis. There is no specific treatment.

Inheritance patterns
There has been rapid increase in the understanding of the genetics of osteopetrosis since 2000. Now it is known that mutation in any one of four genes (CAII, ATP6i, ClCN7, GL) is responsible for over three quarters of cases, with no causative gene having so far been identified in the remaining quarter. Autosomal recessive disease may result from mutation of any of these genes. Autosomal dominant disease results from mutations of ClCN7 in most cases.

Prenatal diagnosis
Accurate antenatal diagnosis is possible in families with known gene mutations by either chorionic villus sampling or amniocentesis from ten weeks of pregnancy onwards. For other families prenatal diagnosis is less reliable and depends on detection of changes in the fetus by X-ray or ultrasound in the last third of pregnancy.

Medical text written November 2000 by Dr C G Steward. Last updated October 2005 by Dr C G Steward, Reader in Stem Cell, Bristol Children's Hospital, Bristol, UK.

Further Online Resources
Medical texts in The Contact a Family Directory are designed to give a short, clear description of specific conditions and rare disorders. More extensive information on this condition can be found on a range of reliable, validated web sites and links to them are included in the CD-ROM version of this Directory. Further information on these resources can be found in our Medical Information on the Internet article.

OSTEOPETROSIS SUPPORT TRUST - OST

Osteopetrosis Support Trust - OST
26 Doniford Road
Williton
Taunton TA4 4SE
Tel: 01984 639416
e-mail: alison@osteopetrosis.co.uk
Web: http://www.osteopetrosis.co.uk

The Trust is a National Registered Charity No. 1013052, established in 1991. OST is a parent-run support group offering support after diagnosis and bereavement and linking families where possible. It is supported by medical and scientific advisers and has information available for families and professionals, details on request (please send SAE). As this is such a rare disease the trust is run by the parents and families of Osteopetrosis sufferers and anyone is welcome to join and support at anytime.

Group details last updated October 2007.