Congenital malformations - Edocr

Chapter 46
Skeletal Dysplasias
PRAVEEN KUMAR
INTRODUCTION
Skeletal dysplasias, also known as osteochondrodysplasias,
refer to a group of disorders which
are characterized by abnormalities in the development,
growth, and maintenance of both bone
and cartilage. 1,2 The osteodysplasias are usually
characterized by osteopenia or osteosclerosis,
whereas chondrodysplasias usually result in
short stature by affecting cartilage and therefore
the linear growth of bones. 3 Some authors subdivide
these disorders into: dysplasias (abnormalities
of bone and/or cartilage growth) and
osteodystrophies (abnormalities of bone and/or
cartilage texture). 4 Multiple bones of the axial
and appendicular skeleton and bones developing
both from endochondral and membranous
ossification are involved and the abnormalities
are intrinsic to bone and cartilage. The phenotypes
in patients with these disorders continue to
evolve throughout life and explain the fact that
many cases of osteochondrodysplasia are diagnosed
later in life. It is important to differentiate
osteochondrodysplasias from dysostoses which
occur as a result of abnormalities of blastogenesis in
the first 6–8 weeks of life resulting in defective bone
formation. 4 Patients with dysostoses have regional
bone abnormalities and the phenotype
remains static throughout life. The skeletal dysplasias
have been classified in many different
ways over the years, but the most commonly used
classification is from the International Working
Group (IWG) on the Classification of Constitutional
Disorders of Bone (CCDB). The last updated
version was published in 2002 and includes
33 groups of osteochondrodysplasias and
3 groups of dysostoses. 5 Although individual
skeletal dysplasias are rare, they are relatively
common as a group and have a significant effect
on morbidity and mortality at all ages. Over 200
skeletal dysplasias have been described and
nearly half of these are lethal which account for
almost 9 per 1000 perinatal deaths. 6 A complete
review of all disorders in this category is beyond
the scope of this book. This chapter provides an
approach to evaluation of common skeletal dysplasias
presenting in perinatal period only.
EPIDEMIOLOGY
Although individual skeletal dysplasias are rare,
they are relatively common as a group with a
reported prevalence rate of 1.1–7.6 per 10,000
births in previous epidemiologic studies. 7 This
wide range of prevalence in different studies is
attributed to differences in case ascertainment,
definition of dysplasias, inclusion age of patients,
and differences in inclusion of still births, and
pregnancy terminations after a prenatal diagnosis.
The study reporting a prevalence rate of 7.6 per
10,000 births was based on inclusion of cases
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