osteogenesis imperfecta type III - progressive deforming
Last reviewed 11/2021
Type III is a severely progressive deforming variety of osteogenesis imperfecta with an autosomal dominant pattern of inheritance.
In this form of the condition the child may be born with fractures and the skull may be well ossified. In this condition there are white sclerae and there may be dentinogenesis imperfecta.
Growth is severely stunted and the child may be of short stature. Repeated fractures occur during childhood and there is progressive deformity of the limbs and spine. There may be kyphoscoliosis that is severe enough to predispose the child to chest disease.
- nearly all osteogenesis imperfecta (OI) cases
are due to heterozygosity of dominant mutations in one or other of the two genes
(COL1A1 and COL1A2) that encode for type I procollagen chains (1)
type 1 procollagen chains form type I collagen, the major structural protein of
the extracellular matrix of bone, skin and tendons
- there have been more than 200 mutations identified so far
- some mutations give rise to a qualitative
type I collagen defect caused by a structural alteration of the collagen molecule.
Other mutations maintain the synthesis of normal collagen, but in reduced quantity
- mutations resulting in qualitative changes in type I collagen generally lead to the most severe forms of OI name
- the broad clinical and biomolecular spectrum mean that any classification is unable to be complete or accurate - however it represents a practical tool for the clinician dealing with management of patients
- these type 1 procollagen chains form type I collagen, the major structural protein of the extracellular matrix of bone, skin and tendons