Children Of Glass Osteogenesis Imperfecta 1 Use Your Knowledge

children of glass: osteogenesis imperfecta 1. use your knowledge of greek/latin prefixes and suffixes to analyze the disease “osteogenesis

Children of Glass: Osteogenesis Imperfecta
1. Use your knowledge of greek/latin prefixes and suffixes to analyze
the disease “Osteogenesis Imperfecta”? What do you think it means?
(Hint: osteo=?, genesis =?, Imperfecta=?)
2. What are some of the common things sean would do as a child that
would break bones?
3. How long could Rebecca (one of the young twins from china) go
without breaking a bone?
4. Describe the procedure of “Rodding”?
5. How many fractures has JoJo had in just his first 2 ½ years of
life?
6. What type of genetic defect causes O.I.? (which chromosome holds
the defect, what has been deleted from the gene?)
7. What types of positive outcomes did Pamidronate(2nd treatment
tried) have for JoJo?
Understanding the
Structure of Bones
Structural Organization of Bone
The structure of bone is very similar to reinforced concrete that is
used to make a building or a bridge. When the building or bridge is
first assembled, an initial frame that contains long steel rods is put
in place. Cement is then poured around these steel rods. The rods and
the cement form a tight union, producing a structure that is strong
and resilient enough to withstand some rocking motion while
maintaining strength. Without the steel rods, the cement would be
brittle and fracture with only minor movement. Without the cement, the
steel rods would have inadequate support and would bend.
The same organization is true of bone. The steel rods that support the
building are collagen rods in bone. The cement that surrounds and
supports the rods is formed by minerals (including calcium and
phosphorous) from the blood that crystallize and surround the rods.
These minerals give the bones strength while the collagen rods provide
resiliency.
Diseases that interfere with the ability of calcium and phosphorous to
be deposited around the collagen rods yield bones that bend, but do
not necessarily break. These diseases are usually diagnosed as
"rickets" and are seen in patients who are deficient in vitamin D.
Diseases in which the steel rods (collagen rods) are abnormal produce
brittle bones and fall under the category of osteogenesis imperfecta
(OI). To understand OI, it is essential to understand why the collagen
rods are abnormal and how the abnormal rods affect the structure of
bone.
Normal versus OI Collagen Rods
Collagen rods are actually formed by a strict interactive arrangement
of rigid collagen fibers (molecules). This arrangement is similar to
the way that bricks and mortar interact to form a brick wall.. A
strong wall requires that the individual bricks be uniform in size and
shape so that they can be aligned in an overlapping manner. The
collagen molecules are also organized in an overlapping manner and
held together by their attachment to themselves and to other molecules
and by the calcium that comes from the blood.
The collagen rods that make up OI bone do not give the skeleton full
strength because the quantity or shape of the rods is abnormal. There
is a defect in the structure or numbers of collagen molecules. Such
defects are the result of a mutation (a change) in the DNA (the
genetic code) within a gene that makes collagen and often causes
severe OI. When such a mutation occurs, a defective blueprint is
produced that tells the cell to produce deformed collagen, resulting
in bad collagen fibers. Even though the body still makes some good
collagen fibers, these fibers attach to bad fibers so that the rods
and, consequently, the bone never becomes very strong.
In OI, the collagen fibers that form the rods are either "kinked" or
broken, so that the structure is inherently unstable. Between one-half
to three-quarters of all collagen fibers that are formed are
defective. The more severe the defect in the collagen fiber, the
weaker the collagen rod, the greater the severity of OI. As more
patients with OI are studied, researchers will be better able to
predict how severe a new case of OI will be based on the location of
the weakness within the collagen fiber.
In contrast to the more severe forms of OI, mild or Type I OI does not
result from the production of bad collagen fibers. Instead, it results
from the underproduction of otherwise normal collagen fibers. In these
patients, the mutation inactivates or knocks out the function of one
of the two collagen genes that we all inherit (one from each parent).
The presence of only half the number of collagen fibers and rods has a
moderate effect on bone strength, but it is not as severe as the
malformation of bone from a normal number of bad collagen fibers.