osteogenesis imperfecta type II - perinatal lethal
Last reviewed 01/2018
Type II is the lethal neonatal form of osteogenesis imperfecta, characterised by multiple fractures that occur in utero. The neonate will have crumpled long bones and beaded ribs. There is poor ossification of the skull. The sclerae, like those found in the type I form, are blue.
Other features include:
- 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