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Osteogenesis imperfecta (OI) is a genetic disorder characterized by bones that break easily, often from little or no apparent cause. There are at least four recognized forms of the disorder, representing extreme variation in severity from one individual to another. For example, a person may have just a few or as many as several hundred fractures in a lifetime (OI foundation).

OI is caused by a genetic defect that affects the body’s production of collagen. It is a defect in either of the two genes that code for collagen I, called COL1A1 on chromosome 17, or COL1A2 on chromosome 7. (OIFE) Collagen is the major protein of the body’s connective tissue and can be likened to the framework around which a building is constructed. In OI, a person has either less collagen than normal, or a poorer quality of collagen than normal that leads to weak bones that fracture easily (Smith). 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.

The signs and symptoms of OI vary greatly depending on the type. There are 4 main types: Type I, Type II, Type III, and Type IV.

Type I

Type I is the most common and mildest type of OI. The bones predisposed to fracture. Most fractures occur before puberty. People with it have normal or near-normal stature. They have loose joints and low muscle tone. The sclera, which is the whites of the eyes, usually have a blue, purple, or gray tint. They have a triangular face. Their spine tends to have a slight curvature. Bone deformity is absent or minimal. It is possible to have brittle teeth. Hearing loss is also possible, often beginning in early 20s or 30s. The collagen structure is normal, but the amount is less than normal. (OI Foundation) Type I is broken down into IA and IB, in which the difference being whether dentinogenesis is present. IA has a life expectancy nearly the same as the general public. The physical activity is limited, and may appear to have no disability at all. The bones have a mottled or wormian appearance, forming small islands. (Isselbacher)

Type II

Type II is the most severe form of OI. It is frequently lethal at or shortly after birth, often due to respiratory problems. In recent years, some people with Type II have lived into young adulthood. They have numerous fractures and severe bone deformities. They have a small stature with underdeveloped lungs. In this type, the collagen is improperly formed. (OI Foundation) This type is broken down into three subgroups: IIA is characterized by a broad, crumpled femora and continuous rib beading, IIB by minimal to no rib fractures, and IIC by a thin femora and ribs with extensive fracturing. While in the uterus, there is poor fetal movement, low fetal weight, poor ossification of the fetal skeleton, hypoplastic lungs, the long bones of the upper and lower limbs are shortened or deformed, and the head is soft. The bones and other tissues are extremely fragile, and massive injuries occur in utero or delivery. The ribs appear beaded or broken and the long bones crumpled. (Isselbacher)

Type III

In Type III the bones fracture easily. The fractures are often present at birth, and x-rays may reveal healed fractures that occurred before birth. They tend to have short stature. The scleras of the eyes have a blue, purple, or gray tint. They have loose joints and poor muscle development in the arms and the legs. They have a barrel-shaped rib cage, triangular face, and a spinal curvature. Respiratory problems are possible. Bone deformity is often severe and brittle teeth are possible. Hearing loss is also possible. In this type, the collagen is improperly formed. (OI Foundation)

Type IV

Type IV is between Type I and Type III in severity. The bones fracture easily, most before puberty. They have a shorter than average stature. The sclera of the eyes is white or near white or normal in color. They have mild to moderate bone deformity, a tendency toward spinal curvature, and a barrel-shaped rib cage. They have a triangular face and brittle teeth are possible. Hearing loss is also possible. In this type, the collagen is improperly formed. (OI Foundation)

Most cases of OI are caused by a dominant genetic defect. Some children with OI inherit the disorder from a parent. Other children are born with OI even though there is no family history of the disorder. In these children, the genetic defect occurred as a spontaneous mutation. Because the defect, whether inherited or due to a spontaneous mutation, is usually dominant, a person with OI has a 50 percent chance of passing on the disorder to each of his or her children. Genetic counselors can help people with OI and their family members further understand OI genetics and the possibility of recurrence. (OI foundation)

Osteogenesis imperfecta is the most common genetic disorder of the bone. It occurs in about 1 in 20,000 live births, and is equally prevalent in all races and both sexes. The Type I OI has a population frequency of about 1 in 30,000. Type II has a birth incidence of about 1 in 60,000. Types III and IV are less common and may be as high as 1 in 20,000. (Isselbacher) The occurrence of OI in families with no history or blue sclera is about 1 in 3,000,000 births. (Smith) The reappearance risks in families is estimated to be 6 to 10%, but is only estimated because most couples choose not to have any more children. 15 to 20% of patients with OI do not carry the gene for abnormal collagen, making many wonder if there is yet another genetic problem undiagnosed at this time. (Smith)

There is not yet a cure for OI. The 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 among people with more severe types of OI. (OI foundation)

A surgical procedure called “rodding” is frequently considered for individuals with OI. This treatment involves inserting metal rods through the length of the long bones to strengthen them and prevent or correct deformities. Several medications and other treatments are also being explored for their potential use to treat OI.

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 to early to draw a conclusion. (Isselbacher)

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 an excellent exercise. Individuals with OI should consult their physician or physical therapist to discuss appropriate and safe exercise. (OI Foundation)

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, in which all of which may deplete bone and intensify bone fragility. (OI Foundation)

False accusations of child abuse may occur in families with children who have milder forms of OI, which were not previously diagnosed. OI is characterized by bones that break easily. A minor accident may result in a fracture; some fractures may occur while a child is being diapered, lifted, or dressed. It is possible for a person with OI to break a bone without being aware of it. Child abuse is also characterized by broken bones. In recent years, Americans have become increasingly aware of this problem and major efforts have been undertaken to protect children. When the fracture seems incompatible with the reported cause of the injury, child abuse is often suspected. And, unfortunately, when false accusations of child abuse occur, families become victimized. (OI Foundation)

“Management of patients with OI should address the child’s functional needs. Even though the degree of disability may be severe, management should not be limited to orthopedic procedures and bracing. Treatment planning should be considered, but not totally based on genetic, anatomical, and biochemical abnormalities. Our experience suggests that clinical grouping based in part on functional potential can be useful in the appropriate management of children with OI.”(Binder) People with OI can lead a healthy life despite the restrictions they have. Doing mild exercise and eating right can help them live a healthier life.

Works Cited

Binder, Helga, MD, et al. “Rehabilitation Approaches to Children With Osteogenesis

Imperfecta: A Ten-Year Experience” Arch Phys Med Rehabil 74 (1993).

Isselbacher, et al. Harrison’s Principles of Internal Medicine New York: McGraw Hill,

1994.