Osteogenesis Imperfecta

All people suffering from osteogenesis imperfecta have relatively softer bones which are perennially susceptible to fractures. Afflicted patients usually appear with a short stature compared to their normal counterparts. The bluish tint found in the sclera of patients is classically seen in the majority of patients. A certain degree of auditory defect is also observable among the afflicted individuals. The defect in collagen type synthesis will sometimes present with hypermobile joints or “loose joints” and they usually have pes planus (flat foot). The defective dentin results in poor dentition in most cases. These patients may also present with bowed legs and arms. Scoliosis and kyphosis are common spinal finding in osteogenesis imperfecta.

The diagnosis of osteogenesis imperfecta is easily clenched with a thorough clinical history and physical examination. A positive history of a bone fracture caused by a little force is very suspicious of the disease. The following diagnostic modalities and tests are further implored for the work up of patients with osteogenesis imperfecta:

• X-ray studies: The radiograph of the child will show multiple fractures and bone deformities characteristic of the bone disease.
• Ultrasound: Sonograms can detect severe osteogenesis imperfecta while the baby is still in the uterus.
• Genetic testing: These tests will identify the mutations of the gene that expresses as osteogenesis imperfecta.
• Skin punch biopsy: Definitive diagnosis can be achieved by a biopsy by the histologic demonstration of defective collagen structures and fibroblasts in the skin and ligaments [7]. 
• Amniocentesis: A chorionic villi sampling through genetic analysis procedures can be done to diagnose the disease even before birth.

There is no cure available yet for osteogenesis imperfecta. However, there are well-established therapies known to allay the symptoms of pain and reduce its complications. The following therapies are available for patients suffering from osteogenesis imperfecta:

• Biphosphonates: This drug are actively given to patients suffering from osteoporosis to foster better bone formation and repair. This will significantly reduce bone pain in osteogenesis imperfecta.
• Regular exercises: Frequent low impact exercises can strengthen the muscles and support the brittle bones from crumbling. 
• Bracing: The use of sturdy or metal bracing in the spine and long bones can help prevent the occurrence of fractures among patients.
• Reconstructive surgery: Complications of osteogenesis imperfecta found in the legs and spine will benefit from reconstructive surgery to restore the ambulation in patients [8]. 
• Plaster casting: Patients presenting with long bone fractures are routinely placed in cast to assist bone healing. However, patients with osteogenesis imperfecta may require a shortened time for casting to avoid the development of osteoporosis of disuse. 
• Psychological support: Children and young adults will need adequate psychological support and therapies to overcome the many challenges associated with the bone disease. 
• Physiotherapy: Patients with severe disability associated with the disease will benefit greatly from physiotherapy and the use of appliances like wheelchairs and canes [9].

There is a wide variation in the outcome of patients suffering from osteogenesis imperfecta in terms of morbidity. The genotypic combination influences directly the severity of disability expressed in each patient [6]. Severe perinatal cases can result to fetal death in utero or death of the infant during the perinatal period. These cases present with several pathologic fractures in the body during autopsies. The life expectancy of patients suffering from osteogenesis imperfecta is comparable to the normal population except for those cases with enduring neurologic and respiratory complications.

Studies have revealed that osteogenesis imperfecta is genetically transmitted from parents to children. The mode of transmission for this bone disease is by means of autosomal dominance. The defective gene has been transmitted from one of the parent or carrier parent to a susceptible offspring, thus, symptoms may vary from parent to child in terms of disability and severity in most cases. The missing gene in the defect codes for collagen type 1 needed for the structural integrity of most long bones in the body [1]. The defective collagen synthesis also gives rise to defective teeth, ligaments and eye sclera.

In general, osteogenesis imperfecta has an incidence rating of 1 case per 20,000 live births. The prevalence of the milder forms of osteogenesis imperfecta is observably higher and often times underdiagnosed in the clinics. In the United States, there are approximately 20,000 to 50,000 people afflicted by this bone defect [2]. The incidence rate is fairly equivalent worldwide but with a slightly higher incidence among two notable tribes in Zimbabwe, Africa. Age of onset for osteogenesis imperfecta varies greatly but first signs of fracture usually start from adolescence to adulthood. There is slight predilection in males than in females but there are no observable racial predilection noted.

The basic pathophysiology seen osteogenesis imperfecta is the absence of one of the two genes responsible for the production of collagen type 1. This collagen is needed to produce sturdy and strong bone, dentin, sclera, and ligaments in the body. This genetic defect accounts for almost 80% of all osteogenesis imperfecta cases [3]. Although genetic science has traced its transmission through either autosomal dominant or autosomal recessive traits, there have been cases documented to have originated from spontaneous mutations or due to gonadal mosaicism [4].

Histologically, bone samples from patients with osteogenesis imperfecta will basically appear osteoporotic with marked decrease in the intracellular matrix formation. The bone trabeculae networks will appear thinned and disorganized [5]. Lamellar bone usually persists between the diaphysis and metaphysis of the long bones. There is also a marked delay in the development of the secondary ossification centers in the long bones. Externally, bones in the skull and the spine will appear thinned and wedged in some areas.

It is imperative that couples with strong familial history of osteogenesis imperfecta should submit for genetic counseling before conceiving [10]. High risk patients must submit to an annual medical examination and physical examination to prevent complication.

Osteogenesis imperfecta is a congenital disease characterized by a defective gene that is unable to produce collagen type 1. The collagen type 1 is an important building block for structural integrity of bones in the body. Osteogenesis imperfecta is characterized by soft and fragile bones, hearing defects, curved spine, and brittle dentition. In some literatures, osteogenesis imperfecta is sometimes referred to as “Brittle bone disease”.

Definition: Osteogenesis imperfecta is a congenital disease characterized by a defective gene that is unable to produce collagen type 1 leading to softer bones that are very prone to fractures.
Cause: Osteogenesis imperfecta is caused by a genetic defect transmitted through autosomal dominance. Spontaneous mutations and gonadal mosaicism are also considered an etiologic cause of the disease.
Symptoms: Patients with osteogenesis imperfecta will present with recurrent bouts of fractures at multiple sites of the body. Patients will present with kyphosis and scoliosis in the majority of cases. Patients will have poor dentition and show a bluish tint in the sclerae.
Diagnosis: A thorough medical history and physical examination will easily reach the diagnosis of osteogenesis imperfecta. X-ray and other imaging tools will reveal multiple fractures and bone deformities among the patients.
Treatment and follow-up: Patients are amply given biphosponate therapy to allay the signs of the concurrent osteoporosis in the disease. Supportive casting and bracing can prevent the occurrence of pathologic fractures in patients. Reconstructive surgery can effectively correct the bone deformities associated with the disease. A regular low impact exercise will strengthen the muscles that supports the weakened bones of the body.

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