What Is Osteogenesis Imperfecta?

Created by Blake Anthony Vardaro

Definition

Osteogenesis Imperfecta is a genetic disorder that causes bones to break and fracture more easily for no apparent cause.

Symptoms

  • Blue tint to the whites of your eyes
  • Multiple bone fractures
  • Early hearing loss
  • Bowed legs and arms
  • Kyphosis(excessive outward curvature of the spine, causing hunching of the back)
  • Scoliosis(curved spine)

How do you become infected/affected?

  • Most cases of Osteogenesis Imperfecta have an autosomal dominant pattern of inheritance, which means one copy of the altered gene in each cell is sufficient to cause the condition. Many people with type I or type IV Osteogenesis Imperfecta inherit a mutation from a parent who has the disorder.
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Type I OI

  • most common and mildest type of OI
  • bones predisposed to fracture (most fractures occur before puberty)
  • normal or near-normal stature
  • loose joints and muscle weakness
  • blue, purple, or gray tint to sclera (whites of the eyes)
  • triangular face
  • tendency toward spinal curvature
  • absent or minimal bone deformity
  • possible brittle teeth
  • possible hearing loss, often beginning in early twenties or thirties
  • normal collagen structure, but less than normal amount
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Type II OI

  • most severe form of OI
  • frequently causes death at birth or shortly after, because of respiratory problems
  • numerous fractures and severe bone deformity
  • small stature with underdeveloped lungs
  • blue, purple, or gray tinted sclera
  • improperly formed collagen
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Type III OI

  • easily fractured bones (Fractures often present at birth, and x-rays may reveal healed fractures that occurred before birth.)
  • small stature
  • blue, purple, or gray tinted sclera
  • loose joints and poor muscle development in arms and legs
  • barrel-shaped rib cage
  • triangular face
  • spinal curvature
  • possible respiratory problems
  • often severe bone deformity
  • possible brittle teeth
  • possible hearing loss
  • improperly formed collagen
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Type IV OI

  • between Type I and Type III OI in severity
  • bones easily fractured (most fractures occur before puberty)
  • smaller than average stature
  • sclera normal in color (i.e., white or near-white)
  • mild to moderate bone deformity
  • tendency toward spinal curvature
  • barrel-shaped rib cage
  • triangular face
  • possible brittle teeth
  • possible hearing loss
  • improperly formed collagen
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Type V OI

  • clinically similar to Type IV OI in appearance and symptoms
  • a dense band seen on x-rays adjacent to the growth plate of the long bones
  • unusually large calluses, called 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), which leads to restriction of forearm rotation
  • sclera normal in color (i.e., white or near-white)
  • normal teeth “mesh-like” appearance to bone when viewed under the microscope
  • dominant inheritance pattern
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Type VI OI

  • clinically similar to Type IV OI in appearance and symptoms
  • slightly elevated activity level of alkaline phosphatase (an enzyme linked to bone formation), which can be determined by a blood test
  • distinctive “fish-scale” appearance to bone when viewed under the microscope
  • diagnosed by bone biopsy
  • unknown whether this form is inherited in a dominant or recessive manner, but researchers believe the mode of inheritance is most likely recessive
  • eight people identified with this type of OI to date
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Type VII OI

  • resembles Type IV OI in many aspects of appearance and symptoms in the first described cases
  • in other instances, similar appearance and symptoms to Type II lethal OI, except infants had white sclera, a small head, and a round face
  • small stature
  • short humerus (arm bone) and short femur (upper leg bone)
  • coxa vara (a deformed hip joint in which the neck of the femur is bent downward) is common; the acutely angled femur head affects the hip socket
  • results from recessive inheritance of a mutation in the CRTAP gene. Partial (10 percent) expression of CRTAP leads to moderate bone dysplasia. Total absence of the cartilage-associated protein has been lethal in all identified cases
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Type VIII OI

  • resembles lethal Type II or Type III OI in appearance and symptoms, except infants have white sclera
  • severe growth deficiency
  • extreme skeletal undermineralization
  • caused by absence or severe deficiency of prolyl 3-hydroxylase activity due to mutations in the LEPRE1 gene
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ALL INFORMATION ON TYPES OF OI FOUND AT:
(http://www.niams.nih.gov/health_info/bone/osteogenesis_imperfecta/overview.asp)

Treatment

Osteogenesis Imperfecta is a genetic disorder so it has no cure, but you can have surgery to help improve the condition.
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Interesting Facts

  • Characterized by breaking of the bones for no apparent reason
  • A surgical procedure called "rodding" is used to support bones in the body and prevent them from breaking
  • You can inherit Osteogenesis Imperfecta from your parents
  • It can cause brittle teeth
  • If a child is born with it, the parent has a 25% chance of having another baby with OI

Mortality Rate

Osteogenesis imperfecta (OI) is a group of closely related inherited diseases characterized by abnormal bone fragility. The current clinical classification system delineates 6 types, one of which (type II) is so severe that mortality is 100%, either intrauterine or perinatal. The types are differentiated by clinical groups, by severity, and by the presence or absence of other features such as blue sclerae or dentinogenesis imperfecta. There are no known previous studies of mortality in OI.

From a registry created in association with the Brittle Bone Society, 743 patients with OI in England and Wales were observed in the period 1980-1993. These were classified into 3 groups (type IA, type III, and types IB, IVA, and IVB combined). Average annual mortality rates were determined in each group by sex and attained age. These rates were compared with 1981 rates in the population of England and Wales, matched by sex and age. Results are given in terms of exposures, observed and expected deaths, and 2 indices of excess mortality: mortality ratios and excess death rates per 1000 person-years.

In type IA, 51.5% of the OI cases overall, there was no significant excess mortality (mortality ratio 108%, based on 15 deaths). In type III, on the other hand, excess mortality was very high in children and still significantly high at ages 15-34 years. In the combined group of types IB, IVA, and IVB, the mortality ratio was 157% in patients aged 45 and up (not significant at the 95% confidence level), but higher ratios at younger ages were significant, even though based on a total of only 5 deaths.

(http://www.ncbi.nlm.nih.gov/pubmed/11558400)