Skeletal Disorder - Osteogenesis Imperfecta

• Disease: Osteogenesis Imperfecta (OI)
  
• Common Name: Brittle Bone Disease
• Age of Onset: Present from conception as a gene abnormality.
• Duration: There is no cure; the disease is present for the victim's entire life. There are some treatment options to make the disease more manageable. Fractures due to the disease decrease throughout one's life time.
  
• Most Common in...: The gene defect is more common in people from Zimbabwe, Nigeria, and South Africa. The reason for this is unknown, but the defective gene is frequently passed down in these regions.
• Cause: There are seven different types of OI. Each type has slightly different effects and is caused by a different gene defect. Types I-IV are caused by COL1A1 and/or COL1A2 genes. The defective gene is autosomal dominant. COL1A1 is found on chromosome 17 and COL1A2 is found on chromosome 7. One could use a Punnett square or have a clinical geneticist predict if a child will inherit the defective gene. The genes produce only half of the normal pro-alpha1(I) collagen chains made in the bones. This lack of type I collagen results in bone fragility and thus OI. OI types V-VII are more rare and will not be discussed here, but the basic concept is the same. A defective dominant gene is passed down that makes the victims bones brittle. This skeletal dissorder is usually hereditary, but there have been reported cases where the gene is newly mutated.
• Symptoms: The following are symptoms that may been seen in most types of OI: multiple fractures, blue or gray whiteness of the eyes, demineralized bone at the site of a previous fracture (appears darker than normal bones on X-rays), wormian bones (extra small bones found in the sutures in the skull), weak bone density, defective collagen producing genes (as shown through culturing skin cells or examining blood). Specifically, type I, has spine curvature, loose joints, poor muscle tone, loss of hearing in children, protruding eyes. Type II has respiratory problems, small stature, and infants with it usually die in the first year of life to lung failure. Type III has bone deformities, respiratory problems, short stature, and the symptoms of type I. Type IV has barrel shaped rib cage, bone deformity, and early hearing loss. These symptoms may all be present, or very few may be present. The most obvious sign is repeated bone fractures due to the weak and deformed bone growth.
• Prognosis: The disease is present from conception. At birth and in early childhood, the above symptoms may be present. The may fall victim to several fractures as a result of poor bone density. As the person ages, more treatment options become available. The disease can be managed to where the victim can live a mostly normal life. He or she will be asked to refrain from highly physical sports like football and soccer, and may have to keep a therapy regiment for the majority of his or her life. Women with OI have an increase in bone fractures later in life as they lose bone during menopause. They can do hormone replacement therapy to reverse this problem. Smoking can take out another 5 percent of a person's bone; so it is very important not to smoke if you have OI.
• Treatment Options: There is no cure for OI. Treatment is meant to increase bone density to reduce the number of fractures a person will have. Fosamax and Pamidronate have been approved to help build bone density. Physiotherapy is used to slowly strengthen one's muscles in an attempt to take some of the stress off of the bones. It is also used to improve one's posture to help proper bone formation. This is hard to administer to children because they will shy away from any movement that will cause pain. Biophosphonates such as alendronate or pamidronate are used to directly increase bone mass. Surgery can be used to insert bone or metal rods to correct bone posture, which could help with the pain of OI. All in all, most of the treatment options for OI are painful techniques to help ease this painful disease. The problems never go away, but the symptoms can be reduced.
• Sources: http://en.wikipedia.org/wiki/Osteogenesis_imperfecta, http://www.nlm.nih.gov/medlineplus/osteogenesisimperfecta.html, http://www.netdoctor.co.uk/diseases/facts/brittlebones.htm