OSTEOGENESIS IMPERFECTA

WHAT IS OSTEOGENESIS IMPERFECTA?

Osteogenesis Imperfecta (OI) is a group of inherited disorders in which 
the most common feature is bones that break easily OI results from a 
defect in the chemical make-up or in the production of collagen, 
(Collagen is the protein "glue" that holds tissues together and gives 
strength to bones.) While there is no cure for OI, early diagnosis and 
treatment can help to ease a person's symptoms and prevent 
complications.

HEREDITY AND GENETICS

This brief section on heredity may answer some of your questions, but we 
encourage you to discuss your concerns with a genetic counselor or with 
a knowledgeable doctor. Contact the March of Dimes for a referral to a 
genetic counseling center in your area.

Remember parents have no control over which genes they pass on to their 
children, and should not feel at fault if one or more of their children 
inherits OI.

How is OI Inherited?

An inherited disorder is one that is passed on from parent to child. it 
is a disorder that results from a defect in one of our 50,000 or so 
genes. Genes are the units of hereditary material that direct the 
development and function of every cell in the body Genes exist in pairs, 
but the reproductive cells called "germ cells" have only one gene from 
each pair. At conception, these genes combine to form new gene pairs 
that determine which features or traits the child inherits.

Most inherited genes function normally. Sometimes, however, a gene 
becomes changed from its original form. This is called a ``mutation" The 
exact reason why mutations occur is usually unknown; but if a mutant 
gene functions improperly it can cause a disease, malfunction or 
malformation. WithOI, it is thought that the mutant OI gene causes 
defects of collagen.

There are different ways in which OI can be inherited: autosomal 
dominant inheritance, autosomal recessive inheritance, or the OI gene 
may arise as a result of a new or "spontaneous" mutation.

Autosomal Dominant Inheritance, in which the OI gene is dominant, is the 
most common inheritance pattern. The dominant gene overrides the effects 
of the normal gene of the pair. Therefore, even when the OI gene is 
paired with a normal gene, the child will get OI. With autosomal 
dominant inheritance, there is a 50% chance that an affected parent will 
have a child with OI. On the other hand, both parents may contribute the 
normal gene, resulting in a 50% chance that the child will not inherit 
the autosomal dominant types of OI.

Autosomal Recessive Inheritance is a pattern in which the disorder is 
inherited only if both genes of the pair are OI genes. In other words, a 
child can only be affected if he or she inherits one OI gene from each 
parent. Parents who have one recessive OI gene are "gene carriers:' (A 
carrier is an individual who carries the Ol gene, but does not have the 
effects of 01.) Autosomal recessive inheritance results in a 25% chance 
that each child will inherit the disorder; a 50% chance that each child 
will be a gene carrier and a 25% chance that the child will inherit the 
normal gene from both parents and be unaffected.

New or Spontaneous Mutations make it possible for a child to get OI 
though neither parent carries the OI gene.

FOUR TYPES OF OSTEOGENESIS IMPERFECTA AND THEIR SYMPTOMS

Type I

There are four distinct types of OI. Type I is the most common. It is 
inherited as an autosomal dominant trait, but may occur as a result of a 
spontaneous mutation. Most people with Type I have an average of 5 to 15 
fractures before puberty Fewer fractures occur after puberty People with 
Type I have one or more of the following features which may be mild to 
moderate in severity:
fragile bones triangular-shaped face blue sclerae (the white part of
the eye), hearing loss beginning in a person's teens, twenties or
thirties curvature of the spine thin, somewhat smooth skin discolored
teeth 

Type II

About 10% of people with OI have Type II. Most often, Type II results 
from a new mutation, although some people have inherited the disorder 
through autosomal recessive inheritance. Type II is a very severe form 
of OI. Infants who are born with Type II have extremely fragile bones. 
They may also have many fractures before birth and may die shortly after 
birth due to complications. Prenatal diagnosis using ultrasound may be 
possible (starting at about the sixteenth week) and should be used in 
families with a known history of OI.

Type III

Approximately 20% of people with OI have Type III. People with Type III 
usually have many spontaneous fractures, with 20 or more fractures 
occurring during the first three years of life. Loose joints and poor 
muscle development of the arms and legs are also common symptoms. 
Prenatal diagnosis may be possible during the early first or second 
trimester of pregnancy. Characteristic features include:
soft bones, which not only break, but bend easily severely deformed
arms and legs collapsed vertebrae and severe curvature of the spine
severely deformed rib cage (thorax) which may cause lung problems poor
development of the teeth (dentinogenesis imperfecta), causing teeth to 
break easily mild to severe hearing loss short stature (some people
may only grow to 3 feet tall) high-pitched voice

Type IV

People with Type IV have characteristics similar to Type I. Type IV is 
most often associated with autosomal dominant inheritance, although some 
people acquire the disorder as a result of a new mutation. Most Type IV 
fractures also occur during childhood, but women often have a recurrence 
of fractures after menopause. Typical features include:
blue sclerae (the whites of the eye) at birth that become white by
adulthood curvature of the spine loose, easily overstretched joints
(extreme double jointedness) poor tooth development (dentinogenesis
imperfecta) 

TREATMENT AND PRECAUTIONS

There is as yet no cure for OI, but various treatments are recommended 
to reduce the severity of symptoms. Anyone experiencing pain should ask 
their doctor to prescribe an appropriate pain medication. Rehabilitative 
therapy such as braces to aid walking, and muscle-strengthening 
exercises are major parts of treatment. Swimming may be recommended 
because it helps strengthen joints and muscles without undue stress.

For some types of OI (especially Type I) fractures usually heal, but 
will require close attention to prevent deformities or prolonged 
disability. If fractures do not heal properly orthopedic surgery may be 
needed to correct deformities, particularly of the limbs and spine. Rods 
are often placed inside the long bones of children to correct 
deformities and to give strength to their arms and legs.

People having difficulty walking due to frequent fractures or 
deformities may be more mobile using a cane, crutches or walker. 
Wheelchairs may be required by some people. Individuals with hearing 
loss can benefit from hearing aids. individuals who have dentinogenesis 
imperfecta (fragile teeth) should ask their dentist about capping their 
teeth early to minimize wear and breakage.

Individuals with OI must naturally take more safety precautions than 
most. At home, avoid using area rugs because they can cause slips and 
falls; install and use hand rails on stairs and in bathtubs; make sure 
counters and tables have rounded corners; keep hallways, stairways and 
rooms well lit - use night lights wherever necessary. Since even minor 
bumps or accidents can fracture a bone, take precautions to avoid large 
crowds, unknowing toddlers or large dogs.

Parents should lift and diaper infants with OI with extreme care, being 
careful to support their limbs at all times. Many parents successfully 
transport their children on a pillow or a foam pad. Contact the 
Osteogenesis Imperfecta Foundation, Inc. for information that addresses 
the care of infants with OI.

If you have children with 01, discuss their symptoms with teachers and 
other caregivers so they will know that frequent fractures are common 
symptoms of OI and not signs of child abuse. Although OI does not affect 
intelligence, medical problems and disabilities may present adjustment 
problems for children in school or in social and family situations. If 
so, you and your child might benefit from short-term psychological 
counseling. You can ask your doctor for a referral.

Though children with OI need special protection, they also need to play 
and have friends. Involve your children in activities they an safely 
enjoy and encourage them to be as independent as possible.

There are special legal rights to education for children with disabling 
disorders. For more information contact the American Juvenile Arthritis 
Organization (AJAO) - a membership organization of the Arthritis 
Foundation concerned with the issues of arthritis and related diseases 
in children. Also request AJAO booklets about the special needs of 
children with chronic illness and how parents and teachers can help.

THE FUTURE

Medical researchers are studying inherited disorders such as OI. By 
analyzing the chemical make-up of collagen and the result of gene 
mutations, they will some day find ways to treat OI more effectively and 
perhaps cure or even prevent it.