Osteogenesis imperfect (OI) or
brittle bone disease is a rare clinically and genetically heterogeneous
systemic disorder of bone and connective tissue.
It is a group of genetic diseases of collagen in which the bones are formed improperly, making them fragile and prone to breaking. (TheFreeDictionary.com, 2017)
Type of OI:
According to the
Osteoporosis and Related Done Disease National Resource Center there are four
type of OI following:
Type I: The mildest and most common type _usually inherited.
Type II: The most severe type _frequently life-threatening.
Type III: Severe type_ usually no family history.
Type IV: Moderate type_ often traced through family lines.
People with OI are born with defective connective tissue (bone,
ligament) or inability to make it because of deficiency of type-I collagen. This
deficiency arises from amino acids substitution of glycine to bulkier amino
acids in collagen triple helix structure which compromises interaction with
other molecules. The body responds by hydrolysing the improper collagen
structure, however, if this does not happen then improper association between
collagen fibre and hydroxyapatite crystals ensure resulting in brittle bones.
Another theory explains the stress state of collagen fibrils at mutation sites
are altered leading to structural failure. These recent findings suggest that
the disease is a multi-level phenomenon occurring at the genetic, macro, micro
and nano levels.
There are many
reasons that causes Osteogensis imperfect. One of the most reasons is the
dominant mutations happen on the gene (COL1A1 or COL1A2). Genetic (genes carry
our hereditary and what make us look like our biological family) which do not
work properly. In fact, people have two copies of most genes that are come from
their parent. If these gens do not work properly that mean there is not enough
collagen in the body or the collagen do not work properly. This is lead to weak
bones that break easily. Secondly, medical characteristics and issues such as
bone deformity, short stature, and lower bone density. Finally, failure of the
osteoclasts (a large multinucleate bone cell which absorbs bone tissue during
growth and healing to resorb none).
Brittle bone disease is genetically inherited. In fact, there is a
50% chance children will have OI if there parent has this disease. Occasionally
a child may be born with OI despite neither parent having the condition.
Sign and symptom:
As mention above
there are many type of OI that mean this disease can range from mild to severe.
In the mild OI the patient has following signs and symptoms: first, the bones break
easily. This is because the density of bone is reducing due to luck of collagen
which is response for produce protein. In fact, fracture of OI very highly from
person to person even the patient have same type of OI or are in same family.
Second, reduce muscular strength or extra skeletal problem. Skeletal deformity is an important
characteristic of OI such as coxa vara (it is a deformity of the hip and it is not rare in OI speciality
in severe form of this disease), whereby the angle between the head and the
shaft of the femur is reduced to less than 120 degrees. In addition,
there will be abnormal curvature of the spine (kyphosis and scoliosis). In
fact, the degree and severity of scoliosis depend on aged of patient. In some
cases the scoliosis associated with vertebra flatting and deformity of ribs which
all causes abnormality of pulmonary function. Third, abnormality in healing of
wound and surgical incisions. Final, Obesity is a serious issue for some
children and adults with OI. Lack of physical activity, small body size and a
diet high in fat, salt and calories can quickly cause a person to be overweight. However, in sever forms of the disease can cause hearing loss,
heart failure, spinal cord problems and permanent deformities. It is important
to note that OI can sometimes be life-threatening if it occurs in babies either
before or after short time of birth.
Doctor cannot always be diagnosed this disease at birth or during early
infancy because there are different types of OI and differing degrees of
severity .The OI Foundation believes that genetic counselling should always be
part of the process when genetic testing for OI is done. The first step doctor
do is collecting information about mutation because it helps them to know the
causes and identifying potential cures. In fact there are many tests which require
to identify OI such as collagen biochemical (skin biopsy), Collagen Molecular Testing (DNA analysis) and Testing for Recessive OI
which give information about defects in the genes controlling
CRTAP or P3H1. Second X-Ray graphs which show abnormality in the bone. For
example head, neck and spine X-Ray graphs show additional small bone kyphoscoliosis (is a deformity of the spine
characterized by abnormal curvature of the vertebral column in two planes
(coronal and sagittal). Also X-Ray graph in chest shows pigeon chest ( chest
wall deformity in which the sternum protrudes inward). Finally MRI graph that can be used to assess
extent of basilar invagination (it is infolding of the base of the skull
that occurs when the top of the C2 vertebra migrates upward).
There is not yet any
care for OI. The only thing which doctor can do are preventing or controlling
the symptoms and develop bony mass and muscle strength.
1- Paediatric Treatment
bisphosphonates and zoledronate which use to increase bone mass. In fact
sometime start in neonatal period if infant can breathe by own.
Physical and occupational therapy:
mobility of the joint and improve function, address joint, and improve
rodding surgery which use to support long bones. Also osteotomies which use to
correct bowing of long bone. Other surgery like fixation use to stabilize the
medication of adult is similar to paediatric.
The aim of
physical therapy is to maintain mobility and adjust to physical changes due to
injury or aging.
many surgeries available such as joint replacement, fracture repair and rod
prognosis for a person with OI different depending on number and severity of
symptoms. The most frequent causes of death for people with OI is respiratory