A.D.A.M. Medical Encyclopedia.

Osteogenesis imperfectaBrittle bone disease

Last reviewed: August 2, 2011.

Osteogenesis imperfecta is a condition causing extremely fragile bones.

Causes, incidence, and risk factors

Osteogenesis imperfecta (OI) is a congenital disease, meaning it is present at birth. It is frequently caused by defect in the gene that produces type 1 collagen, an important building block of bone. There are many different defects that can affect this gene. The severity of OI depends on the specific gene defect.

OI is an autosomal dominant  disease. That means if you have one copy of the gene, you will have the disease. Most cases of OI are inherited from a parent, although some cases are the result of new genetic mutations.

A person with OI has a 50% chance of passing on the gene and the disease to their children.

Symptoms

All people with OI have weak bones, which makes them susceptible to fractures. Persons 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 their eyes (blue sclera)

Multiple bone fractures

Early hearing loss (deafness)

Because type I collagen is also found in ligaments, persons 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

Scoliosis (S-curve spine)

Signs and tests

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 using a skin punch biopsy. Family members may be given a DNA blood test.If there is a family history of OI, chorionic villus sampling   may be done during pregnancy to determine if the baby has the condition. However, because so many different mutations can cause OI, some forms cannot be diagnosed with a genetic test.

The severe form of type II osteogenesis imperfecta can be seen on ultrasound when the fetus is as young as 16 weeks.

Treatment

There is not yet a cure for this disease. However, specific therapies can reduce the pain and complications associated with OI.

Bisphosphonates are drugs that have been used to treat osteoporosis. They have proven to be very valuable in the treatment of OI symptoms, particularly in children. These drugs can increase

the strength and density of bone in persons with OI. They have been shown to greatly reduce bone pain and fracture rate (especially in the bones of the spine).

Low impact exercises such as swimming keep muscles strong and help maintain strong bones. Such exercise can be very beneficial for persons with OI and should be encouraged.

In more severe cases, surgery to place metal rods into the long bones of the legs may be considered to strength the bone and reduce the risk of fracture. Bracing can also be helpful for some people.

Reconstructive surgery may be needed to correct any deformities. Such treatment is important because deformities (such as bowed legs or a spinal problem) can significantly affect a person's ability to move or walk.

Regardless of treatment, fractures will occur. Most fractures heal quickly. Time in a cast should be limited since bone loss (disuse osteoporosis) may occur when you do not use a part of your body for a period of time.

Many children with OI develop body image problems as they enter their teenage years. A social worker or psychologist can help them adapt to life with OI.

Expectations (prognosis)

How well a person does depends on the type of OI they have.

Type I, or mild OI, is the most common form. Persons with this type can live a normal lifespan.

Type II is a severe form that is usually leads to death in the first year of life.

Type III is also called severe OI. Persons with this type have many fractures starting very early in life and can have severe bone deformities. Many become wheelchair bound and usually have a somewhat shortened life expectancy.

Type IV, or moderately severe OI, is similar to type I, although persons with type IV often need braces or crutches to walk. Life expectancy is normal or near normal.

There are other types of OI, but they occur very infrequently and most are considered subtypes of the moderately severe form (type IV).

Complications

Complications are largely based on the type of OI present. They are often directly related to the problems with weak bones and multiple fractures.

Complications may include:

Hearing loss (common in type I and type III)

Heart failure (type II)

Respiratory problems and pneumonias due to chest wall deformities

Spinal cord or brain stem problems

Permanent deformity

Calling your health care provider

Severe forms are usually diagnosed early in life, but mild cases may not be noted until later in life. Make an appointment with your health care provider if you or your child have symptoms of this condition.

Prevention

Genetic counseling is recommended for couples considering pregnancy if there is a personal or family history of this condition.

References

1. Marini JC. Osteogenesis imperfecta. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds.Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 692.

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002540/

Osteogenesis Imperfecta

Cause

Symptoms and Signs

Description

Doctor Examination

Treatment

Living with Ostogenesis Imperfecta

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Osteogenesis imperfecta (OI) literally means "imperfectly formed bone." People with osteogenesis imperfecta have a genetic defect that impairs the body's ability to make strong bones.

Some people have a more severe form of the condition. Their bones break easily and they may break hundreds of bones during their lives. Many people, however, have a milder form of OI, and go through life with few fractures.

Cause

In people with osteogenesis imperfecta, one of the genes that tells the body how to make a specific protein does not function. This protein (type I collagen) is a major component of the connective tissues in bones. Type I collagen is also important in forming ligaments, teeth, and the white outer tissue of the eyeballs (sclera).

As a result of the defective gene, not enough type I collagen is produced, or the collagen that is produced is of poor quality. In either case, the result is fragile bones that break easily but can heal at a normal rate.

In most cases of OI, children inherit the defective gene from one of their parents. But, the child's symptoms and the degree of disability can be very different from that of the parent.

In some children, neither parent has osteogenesis imperfecta. In these cases, the genetic defect is a spontaneous mutation (change) in the gene, and it stops functioning correctly.

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Symptoms and Signs

There are different types of osteogenesis imperfecta with symptoms that range from mild to severe. Each person with the condition may have a different combination of symptoms. All people with OI, however, have weaker bones.

Some common symptoms of OI include:

Short stature Triangular-shaped face Breathing problems Hearing loss Brittle teeth Bone deformities, such as bowed legs or scoliosis

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Description

This 16-year-old boy has bone deformities in both his shinbones that have not yet been straightened with surgery.

Courtesy of Texas Scottish Rite Hospital for Children.

Osteogenesis imperfecta is relatively rare. Approximately 20,000 to 50,000 people in the United States have the condition.

In many children with osteogenesis imperfecta, the number of times their bones fracture decreases significantly as they mature. However, osteogenesis imperfecta may become active again after menopause in women or after the age of 60 in men.

Scoliosis, or curvature of the spine, is a problem for many children with osteogenesis imperfecta.

There are several types of osteogenesis imperfecta and they vary in severity and characteristics. As scientists have discovered new genetic problems causing OI, new types of the disorder have been recognized. All types of the disorder, however, have symptoms and severity that fall somewhere within the range of the first four types recognized. These four types are described below.

Type I Osteogenesis ImperfectaType I osteogenesis imperfecta is the most common and mildest type of this disease. While the structure of the collagen is normal, there is less collagen than there should be. There is little or no bone deformity, although the bones are fragile and easily broken. The effects of osteogenesis imperfecta may extend to the teeth, making them prone to cavities and cracking. The whites of the eyes may have a blue, purple, or gray tint.

Type II Osteogenesis ImperfectaType II osteogenesis imperfecta is the most severe form of the disease. The collagen does not form properly. Bones may break even while the fetus is in the womb. Many infants with type II osteogenesis imperfecta do not survive.

Type III Osteogenesis ImperfectaType III osteogenesis imperfecta also has improperly formed collagen and often severe bone deformities, plus additional complications. The infant is often born with fractures. The whites of the eyes may be white, blue, purple, or gray. People with type III osteogenesis imperfecta are generally shorter than average. They may have spinal deformities, respiratory complications, and brittle teeth.

Type IV Osteogenesis ImperfectaType IV osteogenesis imperfecta is moderately severe, with improperly formed collagen. Bones fracture easily, but the whites of the eyes are normal. Some people with type IV osteogenesis imperfecta may be shorter than average and may have brittle teeth. Bone deformities are mild to moderate.

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Doctor Examination

In many cases, broken bones that occur with little or no force are the first sign of osteogenesis imperfecta, and will cause your doctor to suspect the condition.

Medical History and Physical ExaminationBecause osteogenesis imperfecta is often inherited, your doctor will discuss family medical history in addition to your child's medical history. Your doctor will also complete a thorough physical examination that includes checking your child's eyes and teeth.

TestsX-rays will provide your doctor with clear images of your child's bones, showing fractures as well as malformations of bone.

Your doctor may take blood or tissue samples for genetic testing. In many cases, these tests are able to identify the mutation, particularly if the parent's mutation is also known.

Ultrasound can often detect severe cases of osteogenesis imperfecta during pregnancy.

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Treatment

While there is no cure for osteogenesis imperfecta, there are ways to improve a child's quality of life. Treatment is individualized and depends on the severity of the disease and the age of the patient. Care is provided by a team of healthcare professionals, including several types of doctors, a physical therapist, a nurse-clinician, and a social worker. Support from a social worker or psychologist is very helpful for both the child and the family, and often becomes even more important during adolescence.

Nonsurgical TreatmentIn most cases, treatment is nonsurgical.

Medication. Medical bisphosphonates, given to the child either by mouth or intravenously, slow down bone resorption. In children with more severe osteogenesis imperfecta, bisphosphonate treatment often reduces the number of fractures and bone pain. These medications must be administered by properly trained doctors and require close monitoring.

Immobilization. Casting, bracing, or splinting fractures is necessary to keep the bones still and in line so that healing can occur.

Exercise. After a fracture, movement and weight bearing are encouraged as soon as the bone has healed. Specific exercises will increase mobility and decrease the risk of future fractures.

Low-impact exercise, such as swimming and walking, can help strengthen bones and the muscles that support them. Exercise is part of a healthy lifestyle for every child.

Surgical TreatmentSurgery may be recommended in cases of:

Repeated fractures of the same bone Fractures that do not heal properly Bone deformity, such as scoliosis

This 14-year-old boy with osteogenesis imperfecta has scoliosis. Scoliosis is a sideways curve of the spine. Instead of a straight line down the middle of the back, this spine has two curves.

Courtesy of Texas Scottish Rite Hospital for Children.

Rodding. Metal rods may be inserted in the long bones of the arms and legs to help reinforce the bone, and subsequently lessen the number of fractures. Some rods are a fixed length and must be replaced as a child grows. Other rods are designed like telescopes, and they expand as a child's bones grow. There are,however, other complications that may occur with telescoping rods. Do not hesitate to ask your orthopaedic surgeon about both rodding options.

Spinal fusion for scoliosis. Although bracing is the usual treatment for scoliosis, it is not often effective in children with osteogenesis imperfecta because the ribs will become deformed from the brace, without preventing the scoliosis from worsening. Spinal fusion, a surgery in which the bones of the spine are realigned and fused together, may be recommended when the scoliosis becomes severe.

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Living with Ostogenesis Imperfecta

Below are some tips developed by the Osteogenesis Imperfecta Foundation for taking care of children with osteogenesis imperfecta. Most importantly, do not feel guilty if your child breaks a bone. Children

must grow and develop, and fractures will occur no matter how careful you are.

Do not be afraid to touch or hold an infant with osteogenesis imperfecta, but be careful. To lift an infant with osteogenesis imperfecta, spread your fingers apart and put one hand between the legs and under the buttocks, and place the other hand behind the shoulders, neck, and head.

Never lift a child with osteogenesis imperfecta by holding him or her under the armpits.

Do not pull on arms or legs or, in those with severe osteogenesis imperfecta, lift the legs by the ankles to change a diaper.

Select an infant car seat that reclines. It should be easy to place or remove your child in the seat. Consider padding the seat with foam and using a layer of foam between your child and the harness.

Be sure your stroller is large enough to accommodate casts. Do not use a sling- or umbrella-type stroller.

Follow your doctor's instructions carefully, especially with regard to cast care and mobility exercises. Swimming and walking are often recommended as safe exercises.

Adults with OI should avoid activities such as smoking, drinking, and taking steroids because they have a negative impact on bone density.

Increasing awareness of child abuse and a lack of awareness about osteogenesis imperfecta may lead to inaccurate conclusions about a family situation. Always have a letter from your family doctor and a copy of your child's medical records handy

http://orthoinfo.aaos.org/topic.cfm?topic=a00051

Fast Factson Osteogenesis Imperfecta

DefinitionOsteogenesis imperfecta (OI) is a genetic disorder characterized by bones that break easily, often from little or no apparent cause. A classification system of different types of OI 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.PrevalenceWhile the number of people affected with OI in the United States is unknown, the best estimate suggests a minimum of 20,000 and possibly as many as 50,000.DiagnosisOI is caused by genetic defects that affect the body’s ability to make strong bones. In dominant (classical) OI, a person has too little type I collagen or a poor quality of type I collagen due to a mutation in one of the type I collagen genes. Collagen is the major protein of the body’s connective tissue. It is part of the framework that bones are formed around. In recessive OI, mutations in other genes interfere with collagen production. The result in all cases is

fragile bones that break easily.It is often, though not always, possible to diagnose OI based solely on clinical features. Clinical geneticists can also perform biochemical (collagen) or molecular (DNA) tests that can help confirm a diagnosis of OI in some situations. These tests generally require several weeks before results are known. Both the collagen biopsy test and DNA test are thought to detect almost 90% of all type I collagen mutations.   A positive type I collagen study confirms the diagnosis of dominant OI, but a negative result could mean that either a collagen type I mutation is present but was not detected or the patient has a form of the disorder that is not associated with type 1 collagen mutations or the patient has a recessive form of OI. Therefore, a negative type I collagen study does not rule out OI. When a type I collagen mutation is not found, other DNA tests to check for recessive forms are available.Clinical FeaturesThe characteristic features of OI vary greatly from person to person, even among people with the same type of OI, and even within the same family. Not

all characteristics are evident in each case. The majority of cases of OI (possibly 85-90 %) are caused by a dominant mutation in a gene coding for type I collagen (Types I, II, III, and IV in the following list). Types VII and VIII are newly identified forms that are inherited in a recessive manner. The genes causing these two types have been identified. Types V and VI do not have a type 1 collagen mutation, but the genes causing them have not yet been identified. The general features of each known type of OI are as follows:Type I

Most common and mildest type of OI.

Bones fracture easily. Most fractures occur before puberty.

Normal or near-normal stature. Loose joints and muscle

weakness. Sclera (whites of the eyes)

usually have a blue, purple, or gray tint.

 Triangular face. Tendency toward spinal

curvature. Bone deformity absent or

minimal. Brittle teeth possible. Hearing loss possible, often

beginning in early 20s or 30s.

Collagen structure is normal, but the amount is less than normal.

Type II Most severe form. Frequently lethal at or shortly

after birth, often due to respiratory problems. 

Numerous fractures and severe bone deformity.

Small stature with underdeveloped lungs.

Tinted sclera. Collagen improperly formed.

Type III Bones fracture easily. Fractures

often present at birth, and x-rays may reveal healed fractures that occurred before birth.

Short stature. Sclera have a blue, purple, or

gray tint. Loose joints and poor muscle

development in arms and legs. Barrel-shaped rib cage. Triangular face.  Spinal curvature. Respiratory problems possible. Bone deformity, often severe. Brittle teeth possible. Hearing loss possible. Collagen improperly formed.

Type IV

Between Type I and Type III in severity.

Bones fracture easily. Most fractures occur before puberty.

Shorter than average stature. Sclera are white or near-white

(i.e. normal in color). Mild to moderate bone

deformity. Tendency toward spinal

curvature. Barrel-shaped rib cage. Triangular face. Brittle teeth possible. Hearing loss possible. Collagen improperly formed.

By studying the appearance of OI bone under the microscope, investigators noticed that some people who are clinically within the Type IV group had a distinct pattern to their bone. When they reviewed the full medical history of these people, they found that groups had other features in common. They named these groups Types V and VI OI. The mutations causing these forms of OI have not been identified, but people in these two groups do not have mutations in the type I collagen genes.Type V

Clinically similar to Type IV in appearance and symptoms of

OI. A dense band seen on x-rays

adjacent to the growth plate of the long bones.

Unusually large calluses (hypertrophic calluses) at the sites of fractures or surgical procedures. (A callus is an area of new bone that is laid down at the fracture site as part of the healing process.)

Calcification of the membrane between the radius and ulna (the bones of the forearm). This leads to restriction of forearm rotation. 

White sclera. Normal teeth.  Bone has a “mesh-like”

appearance when viewed under the microscope. 

Dominant inheritance patternType VI

Clinically similar to Type IV in appearance and symptoms of OI.

The alkaline phosphatase (an enzyme linked to bone formation) activity level is slightly elevated in OI Type VI. This can be determined by a blood test. 

Bone has a distinctive “fish-

scale” appearance when viewed under the microscope.

Diagnosed by bone biopsy. Whether this form is inherited in

a dominant or recessive manner is unknown, but researchers believe the mode of inheritance is most likely recessive.

Eight people with this type of OI have been identified.

Recessive Forms of OIAfter years of research, two forms of OI that are inherited in a recessive manner were discovered in 2006. Both types are caused by genes that affect collagen formation. These forms provide information for people who have severe or moderately severe OI but who do not have a primary collagen mutation.Type VII

The first described cases resemble Type IV OI in many aspects of appearance and symptoms.

In other instances the appearance and symptoms are similar to Type II lethal OI, except infants had white sclera, a small head and a round face.

Short stature. Short humerus (arm bone) and

short femur (upper leg bone) 

Coxa vera is common (the acutely angled femur head affects the hip socket).

Results from recessive inheritance of a mutation to the CRTAP (cartilage-associated protein) gene. Partial function of CRTAP leads to moderate symptoms while total absence of CRTAP was lethal in all 4 identified cases.

Type VIII Resembles lethal Type II or Type

III OI in appearance and symptoms except that infants have white sclera.

Severe growth deficiency. Extreme skeletal under

mineralization. Caused by a deficiency of P3H1

(Prolyl 3-hydroxylase 1) due to a mutation to the LEPRE1 gene.

Inheritance FactorsMost cases of OI (85-90%) are caused by a dominant genetic defect. This means that only one copy of the mutation carrying gene is necessary for the child to have OI. Children who have the dominant form of OI have either inherited it from a parent or, when the parent does not have OI, as a spontaneous mutation.Approximately 10-15 percent of cases

of OI are the result of a recessive mutation. In this situation, the parents do not have OI, but both carry the mutation in their genes. To inherit recessive OI the child must receive a copy of the mutation from both parents.When a child has recessive OI, there is a 25 percent chance per pregnancy that the parents will have another child with OI. Siblings of a person with a recessive form of OI have a 50 percent chance of being a carrier of the recessive gene. DNA testing is available to help parents and siblings determine if they are carriers of this type of gene mutation.A person with a form of OI caused by a dominant mutation has a 50 percent chance of passing on the disorder to each of his or her children. If one parent has OI because of a recessive mutation, 100 percent of their children will be carriers of the recessive OI mutation. Whether any of these children will have OI will depend on their inheritance from the other parent. Genetic counselors can help people with OI and their family members further understand OI genetics and the possibility of recurrence, and assist in prenatal diagnosis for those who wish to exercise that option. For more information on OI inheritance, see the

OI Foundation fact sheet titled “Genetics.”TreatmentThere is not yet a cure for OI. Treatment is directed toward preventing or controlling the symptoms, maximizing independent mobility, and developing optimal bone mass and muscle strength. Care of fractures, extensive surgical and dental procedures, and physical therapy are often recommended for people with OI. Use of wheelchairs, braces, and other mobility aids is common, particularly (although not exclusively) among people with more severe types of OI.People with OI are encouraged to exercise as much as possible to promote muscle and bone strength, which can help prevent fractures. Swimming and water therapy are common exercise choices for people with OI, as water allows independent movement with little risk of fracture. For those who are able, walking (with or without mobility aids) is excellent exercise. People with OI should consult their physician and/or physical therapist to discuss appropriate and safe exercise.Children and adults with OI will also benefit from maintaining a healthy weight, eating a nutritious diet, and

avoiding activities such as smoking, excessive alcohol and caffeine consumption, and taking steroid medications — all of which may deplete bone and make bones more fragile. For more information on nutrition, see the OI Foundation fact sheet titled “Nutrition.”A surgical procedure called “rodding” is frequently considered for people with OI. This treatment involves inserting metal rods through the length of the long bones to strengthen them and prevent and/or correct deformities. For more information, see the OI Foundation’s fact sheet on “Rodding Surgery.”Several medications and other treatments are being explored for their potential use to treat OI. These include growth hormone treatment, treatment with intravenous and oral drugs called bisphosphonates, an injected drug called teriparatide (for adults only) and gene therapies. It is not clear if people with recessive OI will respond in the same manner as people with dominant OI to these treatments. The OI Foundation provides current information on research studies, as well as information about participating in clinical trials.Prognosis

The prognosis for a person with OI varies greatly depending on the number and severity of symptoms. Respiratory failure is the most frequent cause of death for people with OI, followed by accidental trauma. Despite numerous fractures, restricted physical activity, and short stature, most adults and children with OI lead productive and successful lives. They attend school, develop friendships and other relationships, have careers, raise families, participate in sports and other recreational activities and are active members of their communities.

 

For more information about osteogenesis imperfecta contact:

Osteogenesis Imperfecta Foundation804 W. Diamond Avenue, Suite 210,

Gaithersburg, MD 20878Tel: 800-981-2663 or 301-947-0083

Fax: 301-947-0456Internet: www.oif.org

E-mail: bonelink@oif.orghttp://www.oif.org/site/PageServer?pagename=fastfacts

History

Patients often have a family history of osteogenesis imperfecta (OI), but most cases are due to new mutations.

Patients most commonly present with fractures after minor trauma.

In severe cases, prenatal screening ultrasonography performed during the second trimester may show bowing of long bones, fractures, limb shortening, and decreased skull echogenicity. Lethal osteogenesis imperfecta cannot be diagnosed with certainty in utero.

Patients may bruise easily. Patients may have repeated fractures after mild trauma.

However, these fractures heal readily. Deafness is another feature. About 50% of patients with type I

osteogenesis imperfecta have deafness by age 40 years.

Physical examination can vary depending on the severity. Degrees of severity may vary among different affected members of the same family.

Type I - Mild formso Patients have no long-bone deformity.o The sclera can be blue or white. Blue sclera may also occur in

other disorders, such as progeria, cleidocranial dysplasia, Menkes syndrome, cutis laxa, Cheney syndrome, and pyknodysostosis.

o Dentinogenesis imperfecta may be present.o Over a lifetime, numbers of fractures can range from 1-60 or

more.o Height is usually normal in individuals with mild forms of

osteogenesis imperfecta.o People with osteogenesis imperfecta have a high tolerance for

pain. Old fractures can be discovered in infants only after

radiographs are obtained for other reasons other than an assessment of osteogenesis imperfecta, and they can occur without any signs of pain.

o Exercise tolerance and muscle strength are significantly reduced in patients with osteogenesis imperfecta, even in the mild forms.

o Fractures are most common during infancy but may occur at any age.

o Other possible findings include kyphoscoliosis, hearing loss (at any age),[8] premature arcus senilis, and easy bruising.

Type II - Extremely severeo Type II is often (but not always) lethal.o Blue sclera may be present.o Patients may have a small nose, micrognathia, or both.o All patients have in utero fractures, which may involved the

skull, long bones, and/or vertebrae.o The ribs are beaded, and the long bones are severely

deformed.o Causes of death include extreme fragility of the

ribs, pulmonary hypoplasia, and malformations or hemorrhages of the CNS.

Type III - Severeo Patients may have joint hyperlaxity, muscle weakness, chronic

unremitting bone pain, and skull deformities (eg, posterior flattening) due to bone fragility during infancy.

o Deformities of upper limbs may compromise function and mobility.

o The presence of dentinogenesis imperfecta is independent of the severity of the osteogenesis imperfecta.

o The sclera have variable hues.o In utero fractures are common.o Limb shortening and progressive deformities can occur.o Patients may have a triangular face with frontal bossing.

Malocclusion is common.

o Basilar invagination is an uncommon but potentially fatal occurrence in osteogenesis imperfecta.

o Vertigo is common in patients with severe osteogenesis imperfecta.

o The incidence of congenital malformations of the heart in children with osteogenesis imperfecta is probably similar to that of the healthy population.

o Hypercalciuria  may be present in about 36% of patients with osteogenesis imperfecta but does not appear to affect renal function.

o Respiratory complications secondary to kyphoscoliosis are common in individuals with severe osteogenesis imperfecta.

o Constipation and hernias are also common in people with osteogenesis imperfecta.

Type IV - Undefinedo This type of osteogenesis imperfecta is not clearly defined.o Whether patient have normal height or whether scleral hue

defines the type has not been established in consensus.o Dentinogenesis imperfecta may be present. Some have

suggested that this sign can be used to divide type IV osteogenesis imperfecta into subtypes a and b.

o Fractures usually begin in infancy, but in utero fractures may occur. The long bones are usually bowed.

causes

Osteogenesis is an inherited disorder. In almost all cases, mode of inheritance in osteogenesis

imperfecta is dominant or involves a new dominant mutation, regardless of the clinical form of osteogenesis imperfecta observed.

A recessive pattern of inheritance has been demonstrated in some families from South Africa.

Some have proposed possible germ-cell mosaicism as an explanation for cases occurring in families with healthy parents that have more than one child with osteogenesis imperfecta.

Syndromes resembling osteogenesis imperfecta (SROI) are usually inherited in recessive fashion.