Osteogenesis imperfecta also called Brittle bone disease; Lobstein’s syndrome
Incidence of Osteogenesis imperfecta
The ‘Brittle bone disease’ is a rare disorder; number of children born with the condition being around 3-4 per 100 000.
There appear to be 4 different types of osteogenesis imperfecta and their incidence varies slightly with each type.
- Type 1: It is the commonest form found in most populations.
- Type 2: It is usually so severe that most babies with this manifestation of brittle bone disease are still-born or die in the first few weeks of life.
- Type 3: It is more frequently found in South Africa amongst the black population.
- Type 4: It is similar to type 1, the main difference being that the ‘whites’ of the eyes do not show the characteristic blue coloration of type 1. Type 1, being the most frequently seen manifestation of this rare condition, will be described.
Causes of Osteogenesis imperfecta
Osteogenesis imperfecta is a genetic disease which is inherited as an autosomal dominant. Biochemically there is a defect in the production of one of the precursors of collagen.
In present condition, there is no such antenatal test for this disorder.
Characteristic Feature Osteogenesis imperfecta:
- Skeletal changes: All bones, particularly those of the arms and legs, are especially fragile and prone to fractures after a minimal amount of injury. Most children with brittle bone disease will have had at least one fracture before they reach five years of age.
- Spinal deformities: Spinal deformities can occur, both kyphosis and scoliosis, later in life, but this rarely occurs during childhood. In adults this can result in a loss of height.
- Eyes: Children with type 1 osteogenesis imperfecta have a marked blue colour to the sclera of their eyes. This unusual coloration of sclera persists throughout life and is a consistent aid which help to diagnose type 1 osteogenesis imperfecta.
- People with type 4 often have blue sclera at birth, but this gradually fades, until by the time adulthood is reached, eyes look completely normal.
- (Vision is not affected by this manifestation.)
- Teeth: Type 1 is further divided into two distinct sub-groups,
- Group A: No dental involvement, only minor skeletal changes.
- Group B: Have teeth which are a yellowish-brown colour. Teeth are of normal size and shape, but can be easily cracked or broken and must be watched for decay due to the excessive wear seen.
- Hearing can be impaired in children with osteogenesis imperfecta. A conductive type of hearing loss is common and is due to deformity in the ear ossicles.
- Blood vessels: Blood vessels are also often excessively fragile, so that in addition to frequent fracture on minimal injury, bruising also occurs easily.
- Skeletal system: The peak ages for fractures are between two and three years, and again between ten and 15 years of age.
- Physiotherapy is often needed after a fracture has healed so that resultant deformity is minimized.
- It is of vital importance in possible cases of child abuse that the diagnosis of osteogenesis imperfecta is known, both from the point of view of easily fractured limbs and excessive bruising following minimal trauma.
- Dental treatment: Teeth must receive on-going and adequate dental care. Advanced dental techniques can change the yellow colour of some children’s teeth to a more attractive colour.
- Hearing: It must be assessed at regular intervals and hearing aids supplied if necessary.
- Trials with calcitonin and fluoride are currently being undertaken in an endeavour to reduce the number of fractures suffered by children with osteogenesis imperfecta.
- Counselling in the adolescent years is of importance so that the young person has an understanding of his/her genetic condition, and the care that he/she should take in the future.
- Pregnancy: Pregnancy in women who are more severely affected can pose problems. The hormonal changes occurring at this time increase laxity of ligaments and so predispose to fractures – again on minimal trauma. Cesarean section is often considered a wise mode of delivery.
A normal lifespan can be expected in the vast majority of people with osteogenesis imperfecta, often with very few problems due to their inherited condition. Careers with minimal physical contact which could result in fractures should be chosen.
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