Osteogenesis imperfecta (OI) is a genetic disorder characterized by bones that break easily, often with little or no apparent cause. It is caused by defects affecting collagen production and bone mineralization. There are 8 types of OI that vary in severity from lethal in infancy to only a few fractures in a lifetime. Treatment focuses on prevention of fractures, maximizing mobility, and physical therapy. Prognosis depends on the type and severity of symptoms but many people with OI live productive lives.

1. Biology 33 Micaela Wolfe

2. Definition
Osteogenesis Imperfecta
(OI) is a genetic disorder
characterized by bones that
break easily, often from little
or no apparent cause. A
classification system of
different types of OI is
commonly used to help
describe how severely a
person with OI is affected.
For example, a person may
have just a few or as many
as several hundred fractures
in a lifetime.
www.oif.org

3. Prevalence
While the number of
people affected with OI
in the United States in
unknown, the best
estimate suggests a
minimum of 20,000 and
possibly as many as
50,000
www.oif.org

4. Causes
OI is caused by
genetic defects that
affect the body’s ability
to make strong bones.
Collagen is a major
protein of the body’s
connective tissue. It is
part of the framework
that bones are formed
around. Collagen is
affected by OI. www.oif.org

5. Genetics
Dominant (classical) OI: A person has too little type I collagen or a poor quality
of type I collagen due to a mutation in one of the type one collagen genes.
Recessive OI: There are mutations in other genes that interfere with collagen
production
www.oif.org

6. Diagnosis
Clinical geneticists can
perform biochemical
(collagen) or molecular
(DNA) tests that can
help confirm a
diagnosis. These tests
take several weeks. A
negative test could
mean there is a
recessive form of OI or
there is a mutation
present.
www.oif.org

7. Clinical Features
Features vary greatly from
person to person, even
among people with the
same type of OI, and even
within the same family.
There are 8 different types
of OI. Types 7 and 8 are
newly discovered, and they
are inherited in a recessive
manner.
www.oif.org

8. Type I
• Most Common and mildest
type of OI
• Bones fracture easily,
occurring mostly before
puberty
• Normal or near normal stature
• Loose joints and muscle
weakness
• Sclera (whites of the eyes)
usually have a blue, purple or
grey tint
• Triangular face
• Tendency toward spinal
curvature
• Bone deformity absent or
minimal
• Brittle teeth possible
• Collagen structure is normal,
but the amount is less than
normal
www.oif.org

9. Type II
• Most severe form
• Lethal at or shortly after
birth (respiratory problems
numerous fractures and
bone deformity)
• small stature and
underdeveloped lungs
• tinted sclera
• collagen improperly
formed
www.oif.org

10. Type III
• Bones fracture easily,
fractures present birth, x-ray
may show healed fractures
before birth
• Short stature
• Sclera with blue, purple or
gray tint
• Loose joints and poor muscle
development in arms and legs
• Barrel-shaped rib cage
• Triangular face
• Spinal curvature
• respiratory problems often
possible
• Collagen improperly formed
www.oif.org

11. Type IV
• Between type I and Type
III in severity
• Bones fracture easily,
most before puberty
• Shorter than average
stature
• Mild to moderate bone
deformity
• Barrel-shaped rib cage
• Triangular face
• Hearing loss possible
• Collagen improperly
formed
www.oif.org

12. Type V
• Clinically similar to Type IV in
appearance and symptoms of
OI
• Calcification of the membrane
between the radius and the
ulna leading to restriction of
forearm rotation
• White sclera
• Normal teeth
• Bone has mesh-like
appearance under the
microscope
www.oif.org

13. Types VI, VII & VIII
• Share many of the same
features
• Severe growth deficiency
• Extreme skeletal under
mineralization
• Short Stature
• Short humorous and short
femur
www.oif.org

14. Treatment
• Not yet a cure for OI
• Treatment directed toward
preventing or controlling
symptoms
• Maximizing independent
mobility, and develop bone
strength
• Physical therapy to build
surrounding muscle
• Braces to help with everyday
tasks
• Mobility aids
www.oif.org

15. Prognosis
• Depends on number
and severity of
symptoms
• Respiratory failure is
the most frequent
cause of death,
followed by accidental
trauma
• Besides fractures,
short stature and
restrictions on physical
activity most live
productive successful
lives
www.oif.org