RT Book, Section A1 Wells, Robert G. SR Print(0) ID 1148952827 T1 Skeletal Dysplasias T2 Diagnostic Imaging of Infants and Children YR 2015 FD 2015 PB McGraw-Hill Education PP New York, NY SN 9780071808392 LK accesspediatrics.mhmedical.com/content.aspx?aid=1148952827 RD 2024/03/19 AB Constitutional errors of bone development include dysostoses, disruptions, and skeletal dysplasias. The dysostoses are malformations of single bones, although multiple sites can be involved. These disorders usually are due to genetic defects that predominantly affect organogenesis. Disruptions are secondary malformations of bones, resulting from extrinsic interference with the normal developmental process by a toxic substance, infection, or transiently expressed gene (e.g., rubella embryopathy). The skeletal dysplasias (osteochondrodysplasias) are intrinsic developmental disorders of chondro-osseous tissue. There are over 400 recognized skeletal dysplasias. Unlike the dysostoses, the genetic defects of the dysplasias affect bone development in both fetal and postnatal life, and have little or no affect on organogenesis. The dysplasias consist of primary lesions in which a genetic mutation is expressed in chondro-osseous tissue (e.g., "classic" dysplasias such as achondroplasia) and secondary dysplasias that are caused by factors extrinsic to the skeletal system (e.g., metabolic disorders). There are also mixed disorders that have features of a dysostosis and a dysplasia, for example, cleidocranial dysostosis and nail-patella syndrome.1–8