Ortopedická protetika Praha sro - Společnost pro pojivové tkáně

INTRODUCTION
Osteogenesis imperfecta is a heritable
disorder characterised by bone fragility
and low bone mass. The effects of this
disorder are sometimes apparent in utero
and are certainly manifest in early childhood
in most cases. Recurrent fractures and
progressive limb and spine deformities
impact greatly on the wellbeing of affected
children and their families. Our knowledge
of the clinical manifestations, underlying
genetics, bone pathology, treatment modalities
and prognosis has advanced greatly in
the last 30 years.
CLASSIFICATION
The most widely used classification of
osteogenesis imperfecta is that proposed
by David Sillence in 1979 in which he
described 4 main types (1). This classification
is based on
– the severity of skeletal manifestations
– the presence or absence of extra skeletal
manifestations
– the inheritance pattern
The majority of cases of OI types I–IV
are associated with mutations in the genes
encoding collagen type 1. Collagen type
1 is the main structural protein of bone,
skin, tendons, dentin and sclera. The collagen
type 1 in OI bones is defective in
quantity and quality. Over 250 mutations in
genes encoding collagen type 1 have been
reported accounting for the great variability
seen in OI (2). Types V–VII have been
added to the classification. Types V–VII
are not associated with mutations in type
I collagen.
Type I
Type I OI is a relatively mild form with
fractures occurring in early childhood.
It has an autosomal dominant pattern of
inheritance. Patients have blue sclerae,
generalised ligament laxity and relatively
normal stature. Dentinogenesis imperfecta
is uncommon in this form. Radiological
features include osteopenia, thin cortices,
fractures, mild bone deformities and
Wormian bones.
Type II
Type II is the most severe form with
multiple fractures occurring in utero and
in the neonatal period. It has an autosomal
dominant pattern of inheritance. Affected
babies are small, hypotonic with dark blue
sclerae. Radiological features include short
wide bones with cortices so thin that they
tend to crumple.
This form of OI is lethal in the perinatal
period, usually because of respiratory failure
resulting from multiple rib fractures.
Type III
Type III is the most severe form compatible
with life. It has an autosomal dominant
pattern of inheritance. Patients have
a triangular facial appearance. They have
very short stature, blue sclerae which become
whiter with age and dentinogenesis
imperfecta. Multiple fractures may occur
in utero and in the neonatal period. The
tendency to fracture persists into adulthood
and is associated with progressive
deformities in the upper and lower limbs
and spine. Radiological features include
osteopenia, thin cortices, narrow diaphy-
POHYBOVÉ ÚSTROJÍ, ročník 14, 2007, č. 3+4 233