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Skeletal dysplasias are generalized disorders of bone and/or cartilage that can produce short stature, osseous deformity, and functional disabilities. More than 372 different genetic disorders of the skeleton have been described by the International Skeletal Dysplasia Society as constitutional diseases of bone1; collectively, dysplasias represent most of the intrinsic disorders of bone with the dysostoses comprising the rest. The overall frequency of the skeletal dysplasias is about 1 in 4000 births,2 making this class of disorders about as common as neurofibromatosis type 1 or Turner syndrome, conditions much better known to the pediatric practitioner.

Skeletal dysplasias have traditionally been divided into the disorders that primarily affect the growth of cartilage and bone, the chondrodystrophies (eg, achondroplasia) and disorders with primary abnormalities of bone that lead to defects in bone density or mineralization (eg, the osteogenesis imperfectas).1,3 Included in the former group are a special class of disorders caused by disorganized development of skeletal components with multiple cartilaginous exostoses, fibrodysplasia ossificans progressiva being the proteotypic syndrome. The dysostoses or disorders of bone structure that cause malformations and functional abnormalities of individual bones are also encompassed under the broader categorization of genetic skeletal disorders. Over the past decade, the distinction between these groups has become increasingly blurred and some mutations can cause abnormalities of bone and cartilage that affect various skeletal elements.1

Skeletal dysplasias can cause substantial morbidity in children and adults, yet many affected individuals lead relatively normal lives, albeit with some special challenges. Historically, the term dwarf has been used to refer to persons with bone dysplasias and disproportionate short stature. Because of the pejorative nature of this label and because it evokes thoughts of a different class of personhood, the use of the term is discouraged. The preferred terminology is to refer to a condition by its medical designation (eg, diastrophic dysplasia); however, the term dwarfism as a medical term is still widely used and accepted by many. This section describes the classification, distinguishing characteristics, and management of selected disorders.

Conventionally, the skeletal dysplasias are often grouped according to the anatomic location of the bones that are most severely affected and the histologic abnormalities that are commonly observed. For example, skeletal dysplasias that affect the spine and the epiphyses are called spondyloepiphyseal dysplasias. However, the criteria used to categorize disorders into this classification are inconsistently applied to many skeletal dysplasias (eg, achondroplasia), and this diminishes its heuristic value. The classification schemes used to organize dysostoses are quite varied. No single system has become widely adopted,1,3 and, accordingly, the clinical presentation and varied expressions of the dysostoses tend to be difficult to remember accurately.

The strategy of classifying malformations according to the developmental pathway that is disrupted can be applied to the skeletal dysplasias.1,3 The logic of the classification is to separate development of the skeleton into three primary phases: patterning, ...

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