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Osteogenesis imperfecta (OI), commonly known as brittle bone disease, is a group of genetic bone disorders. People with OI do not produce enough good quality collagen to produce healthy, strong bones. Collagen is an important protein and without a good enough supply the bones are weak and break very easily.
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.
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
There are no known cures for osteogenesis imperfecta, with the emphasis being on prevention of breakages. Those with OI are advised to exercise, maintain a positive diet and generally lead a healthy life.
One severe method of treatment is a procedure called rodding. This involves the insertion of metal rods through the length of the bone in order to strengthen them.
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