*** WHAT IS OI ***
Osteogenesis Imperfecta (OI) is a rare heritable disorder
of the connective tissue. Literally OI means imperfect bone formation.
This refers to the most prominent feature of OI: bone fragility. Without a clear
immediate cause the bones of an affected person may fracture. This can happen
at any age, even before birth. There are various synonyms
for OI in most languages.
Symptoms of OI
Fragility differs widely from person to person, so the number of fractures can vary from a few
to over a hundred. All connective tissue is involved, not only that in bone.
Besides bone fractures this may cause a variety of symptoms like:
- curvature of arms, legs or spine (scoliosis or kyphosis)
- deformities of the skull,
- triangular face,
- small stature,
- extreme laxity of the joints,
- luxations,
- easy bruising (haematoma),
- blue sclerae,
- hearing loss,
- abnormal teeth (dentinogenesis imperfecta),
- heart valve insufficiency,
- basilar impression,
- extreme tiredness,
- excessive sweating,
- OI can lead to physical disability, requiring the use of crutches or a wheelchair.
It must be stressed that:
- An affected person may show some but usually does not show all these symptoms.
- Many people are only very lightly affected and show hardly any symptoms at all.
- OI expresses itself very individually.
- It is variable between persons and unpredictable per person.
Classification
In 1979 Sillence proposed a classification of OI in
4 types based on the clinical features. With some minor alterations this classification
is still used.
It is not always possible to determine the OI type for every individual.
Diagnosis
OI can be quite difficult to diagnose.
Many doctors are not familiar with it, and many cases go undetected.
It is a myth that all people with OI have blue sclerae. Only a certain percentage of people with
OI have blue sclerae.
Occasionally child abuse is suspected when the child in fact has OI, this is a particularly
frustrating experience for the family involved.
If you think that you or your child may have OI ask your
national OI society to direct you to a specialist who is familiar with OI.
Cause of OI
In most cases OI is caused by a defect in either of the two genes that code for collagen I, i.e.
COL1A1 on chromosome 17 or COL1A2 on chromosome 7. The defect disturbs the production
of collagen.
In OI type I too little, but normal, collagen is produced.
In the other types the collagen is of bad structural quality, while the amount of collagen may be reduced as well.
Treatment
It is not expected that the cause of OI can be eliminated in the near future. Therefore OI can not
be cured at the moment. However, careful treatment can alleviate the circumstances.
Treatments are aimed at reducing the impact of the consequences and at the prevention of
complications. Often this calls for an integral management plan, which may encompass:
orthopedic treatment of fractures, hearing improvement, dental intervention, physical therapy,
psychological assistance, genetic counselling and DNA testing, social advisory, ergotherapy
with advice on crutches and wheelchairs and other equipment, sometimes also dietary advice.
Attention should be given to the prevention of osteoporosis, as people with OI are more
vulnerable to this than other people.
Recently several types of bisphosphonates have been used as drugs with apparently good results, but it is still too early to draw
conclusions.
Prognosis
Because of the individual variability of OI it is impossible to make general statements about the
prospects of an affected person. It is recommended to seek personal advice.
In many cases fragility diminishes after puberty for reasons still unknown.
Inheritance
OI is dominantly inheritable, which means that when one of the parents has OI then for each
newborn child the chance to be affected is 50%.
In many cases OI is not inherited but is caused by a mutation. In these cases none of the parents
shows any sign of OI. The mutation is again dominantly inheritable.
For further details see the page on inheritance.
The issue is further complicated by the possibility of mosaicism.
Because of the complexity of the matter it is recommended to seek personal genetic advice.
Incidence
OI is a rare disorder. Its incidence is estimated at 1:10.000 to 15.000. This estimate is a lower
limit because light forms of the disease are quite often not recognised. OI occurs in all races and
is independent of gender.
Only 0.008% of the world population is affected by OI. This means that at present there are
about 0.5 Million persons with OI in the world.
In Australia one may expect at least
1220 people suffering from OI in some form.
Details on the OIFE members can be found on the
statistics page.
Life & OI
In spite of the restrictions that OI may impose People with OI can lead a happy life as a valued member
of society. Many people with OI live independently and pursue careers (some are even
famous). They can be married or living in stable relationships and have children.
Mutual support by exchange of experience and information is of prime importance for people
with OI and their families.
Please contact your national OI
society for further information and help.
page last updated 31 July 2005