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Information About Osteogenesis Imperfecta

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  Brittle Bone Disease
 
Osteogenesis imperfecta (OI), commonly known as brittle bone disease, is a group of genetic bone disorders. People with OI either have less collagen than normal or the quality is poorer than normal. As collagen is an important protein in bone structure this impairment causes those with the condition to have weak or fragile bones.

As a genetic disorder, OI is a autosomal dominant defect. Most people with OI receive it from a parent but it can also be an individual (de novo or "sporadic") mutation.

Types

There are four types of OI, though the symptoms range from person to person. Type I is the most common and mildest form, followed by Type IV, Type III and Type II. A Type V has been proposed based on studies of Type IV.

Type I

Collagen is normal but not of a high enough quantity:

  • Bones fracture easily, especially before puberty
  • Slight spinal curvature
  • Loose joints
  • Poor muscle tone
  • Discolouration of the sclera (whites of the eyes)
  • Early loss of hearing

Type II

Collagen is not of a sufficient quality or quantity

  • Most cases die before adulthood
  • Severe respiratory problems due to underdeveloped lungs
  • Severe bone deformity and small stature

Type III

Collagen quantity is sufficient but is not of a high enough quality

  • Bones fracture easily, sometimes even before birth
  • Bone deformity, often severe
  • Respiratory problems possible
  • Short stature, spinal curvature and barrel-shaped rib cage
  • Loose joints
  • Poor muscle tone in arms and legs
  • Discolouration of the sclera (whites of the eyes)
  • Early loss of hearing

Type IV

Collagen quantity is sufficient but is not of a high enough quality

  • Bones fracture easily, especially before puberty
  • Short stature, spinal curvature and barrel-shaped rib cage
  • Bone deformity is mild to moderate
  • Discolouration of the sclera (whites of the eyes)
  • Early loss of hearing

Treatment

At present there is no cure for OI so treatment is aimed at maintaining mobility and strengthening bones as much as possible.

Physiotherapy is used to strengthen muscles and improve motility in a gentle manner which minimises bone breakages. This often involves hydrotherapy and the use of support cushions to improve posture. Individuals are encouraged to change positions regularly throughout the day in order to balance the muscles which are being used and the bones which are under pressure. One of the biggest problems is that children often develop a fear of trying new ways of moving due to movement being associated with pain. This can make physiotherapy difficult to administer to young children.

With adaptive equipment such as crutches, splints or grabbers and modifications to the home many individuals with OI can obtain a significant degree of autonomy.

Surgery can be carried out to insert metal rods along the long bones to improve strength however this can have the side effect of reduced joint mobility, though not always. Spinal fusion can be performed to correct scoliosis although the inherent bone fragility makes this operation more complex in OI patients. Surgery for basilar impressions can be carried out if pressure being exerted on the spinal cord and brain stem is causing neurological problems.

Infections are treated as and when they occur with the appropriate antibiotics and antiseptics. In severe cases aminohydroxypropylidene bisphosphonate can be administered intravenously to reduce the incidence of bone fracture and increase bone density. Bisphosphonates can also be administered orally in less severe cases to increase bone density however they only significantly improve bone density if used before adulthood while the bones are still growing.

History and alternative names

The condition, or types of it, have had various other names over the years and in different nations. Among some of the most common alternatives are Ekman-Lobstein syndrome, Vrolik syndrome, and the colloquial glass-bone disease. The name "Osteogenesis Imperfecta" dates to at least 1895 and has been the usual medical term in the twentieth century to present. The current four type system began with Sillence in 1979. An older system deemed less severe types "Osteogenesis Imperfecta Tarda" while more severe forms were deemed "Osteogenesis Imperfecta Congenita." As this did not differentiate well, and all forms are congenital, this has since fallen out of favour.

The condition has been found in an Ancient Egyptian mummy from 1000 BC. The earliest studies of it began in 1788 with the Swede Olof Jakob Ekman. He described the condition in his doctoral thesis and mentioned cases of it going back to 1678. In 1831 Edmund Axmann described it in himself and two brothers. Johann Friedrich Georg Christian Martin Lobstein dealt with it in adults in 1833. Willem Vrolik did work on the condition in the 1850s. The idea that the adult and newborn forms were the same came in 1897 with Martin Benno Schmidt.

Frequency is approximately the same across groups, but for unknown reasons the Shona and Ndebele of Zimbabwe seem to have a higher proportion of Type III to Type I than other groups would. Although a similar pattern was found in segments of the Nigerian and South African population. In these varied cases the total number of OIs of all four types was roughly the same as any other ethnicity.

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