Osteogenesis Imperfecta:
It represents the most common type of inherited bone disease. Abnormal collagenous maturation results in bone with a thin Cortex, fine trabeculation and diffuse osteoporosis. In patients suffering with Osteogenesis Imperfecta upon fracture healing will occur but will be associated with an exuberant callus formation in the fractured area.
Definition:
It is a heterogenous group of heritable disorders characterized by impairment of collagen maturation.
Osteogenesis Imperfecta is a disorder which arises due to Heterozygosity for mutations in one of the two genes responsible for guiding the formation of Type I collagen. The Genes responsible COL1A1 gene on chromosome 17 and COL1A2 gene on chromosome 7.
This disease in important in dental aspect as Collagen forms a major portion of Bone, Dentin and also Ligaments, Sclerae, ligaments and skin. Osteogenesis imperfect is divided into 4 types based on the severity and parts affected. The 4 types will be explained in detail later on in the post.
This disease represents the most common type of inherited bone disease. Abnormal collagenous maturation results in bone with a thin Cortex, fine trabeculation and diffuse osteoporosis. In patients suffering with Osteogenesis Imperfecta upon fracture healing will occur but will be associated with an exuberant callus formation in the fractured area.
Clinical Features:
It is a Rare Disorder and not commonly seen in all its types.
Incidence: 1 in 8000 individuals are affected by Osteogenesis Imperfecta and many are born dead (Stillborn) or die shortly after birth who are suffering with this disease.
Genetic: Both the Autosomal Dominant and recessive hereditary patterns occur and in many cases these are Sporadic.
Family: The severity of Osteogenesis imperfecta differs widely in affected members of a single family.
Clinical findings: Bone Fragility, Blue Sclera, Hearing Loss (Hypoacusis), Spine and Long Bone deformity, altered teeth, Joint hyperextensibility.
Oral Findings:
- Many findings seen in this disease are similar to Dentinogenesis Imperfecta.
- Both the Primary and Permanent dentition are affected and both teeth show a Blue to Brown translucent colour.
- An increased prevalence of Class 3 malocclusion is seen in patients of Osteogenesis Imperfecta which is due to Maxillary Hypoplasia associated with or without Mandibular Hyerplasia.
Radiographic Features:
- Osteogenesis imperfect includes Osteopenia, Bowing, Angulation or deformity of the long bones, multiple fractures and wormian bones in the skull.
- Wormian bones consists of ten or more sutural bones that are 6 x 4 mm in diameteror larger and arranged in a mosaic pattern.
- Wormian bones are not specific and can be seen in other processes such as Cleidocranial Dysplasia.
- Radiographically it is identical to Dentinogenesis Imperfecta.
- Premature Pulpal Obliteration is seen
- Shell Teeth are rarely seen in Osteogenesis imperfect
- Panaromic Radiographic reveal Multifocal radiolucencies, mixed radiolucencies or radiopacities that resemble those seen in florid cement-osseous dysplasia.
- Predominantly radiopaque these areas are sensitive to inflammation and undergo sequestration easily. In such patients marked coarseness also is noted in the remainder of the skeleton.
Histologic Features:
- Osteoblasts are seen in the affected Bone
- Bone Matrix protein is reduced markedly
- Bone architecture remains immature throughout life
- There is a failure of woven bone to become transformed to lamellar bone
Types of Osteogenesis Imperfecta:
The Classification is based on the severity of the disease and also the parts of the body which are affected.
Type I Osteogenesis Imperfecta:
- It is the mildest form and most commonly occurring.
- It is Inherited as an Autosomal Dominant trait.
- Hypermobile joints and Easy Bruising because of capillary fragility are commonly seen.
- Hearing loss is seen before 30 years of age and in older patients without hearing loss suffer from hearing deficits.
- Bone fragility is seen which is mild to moderately severe.
- Fractures are present in 10% of the children at birth.
- Most fractures are seen in pre school period and are less common after puberty.
- Teeth: Some patients have Opalescent dentin and the others have normal dentin.
- Blue Sclera is an important finding in this type
Type II Osteogenesis Imperfecta:
- It is the most severe form of Osteogenesis Imperfecta at Birth.
- Both Autosomal recessive and dominant patterns may occur and many cases appear to be Sporadic.
- Extreme Bone fragility and Frequent fractures are seen in patients suffering from this type.
- Fractures occur in children even during birth because of the fragility of bones.
- Many children are Born Dead (Stillborn) and those who survive during birth die before the age of 4 weeks.
- Blue Sclera is seen.
- Opalescent Teeth are present in patients.
Image Courtesy: www.nejm.org
- It is the most severe form of Osteogenesis Imperfecta in patients who have survived beyond the perinatal period.
- Both Autosomal Dominant and Recessive hereditary patterns are seen.
- These individuals show moderately severe to severe Bone Fragility.
- Fractures may be present at birth, but mortality rate in Infancy is seen.
- One third of the children survive till adulthood but majority of the individuals die during childhood usually from Cardiopulmonary complications caused by kyphoscoliosis.
- Sclera is Normal or Pale Blue or Gray at birth and as age progresses the discoloration fades off.
- Hearing loss and Ligamentous Laxity is common.
- Some patients have Opalescent Dentin and others have normal teeth.
Type IV Osteogenesis Imperfecta:
- It is inherited as an Autosomal Dominant Trait.
- Mild to Moderately Severe bone fragility is seen in this type.
- Sclera may be pale blue in early childhood and this Blue color fades off as the child grows older.
- 50% of the Children are Born with Fractures.
- The Frequency of Fractures decreases after Puberty, but some patients do not have fractures anytime is their life due to this condition.
Treatment for Osteogenesis Imperfecta:
There is No Treatment for Osteogenesis Imperfecta
Management of Fractures as they occur is the only Treatment which can be done
Bleeding disorders should be kept in mind before going for any treatment plan in these patients and the presence of Cardiac malformations along with risk of hyperthermia should be kept in mind.
Intubation may be a big hassle because the brittle Mandible and Cervical vertebrae may fracture because of the force applied in Kyphoscoliosis patients.
Dental Treatment:
- Due to the presence of Opalescent Dentin there is presence of severe Attrition and consequent Tooth loss is seen.
- In these patients removable dentures is the only treatment plan to replace missing teeth as the use of implants might not be supported by the bone.
- In Class III malocclusion cases Orthognathic surgery can be advised which should be considered keeping in mind medical abnormalities associated.
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