The chondrodysplasia are a heterogeneous group of disorders that have been classified on the basis of clinical, radiographic, and pathologic criteria. We have evaluated an unusual child with short-limbed dwarfism, manifested at birth, who does not appear to have any of the presently classified disorders. This child has a unique deficiency of both primary and secondary enchondral ossification, which appears to be secondary to a defect in chondroosseous transformation. Clinically this disorder can be classified in the general group of nonlethal types of short-limbed dwarfism manifested from birth. There were no additional distinctive extraskeletal anomalies, with the exception of communicating hydrocephalus. The radiographic findings appear unique: deficient primary enchondral ossification at the base of the skull, pelvis, and vertebral bodies; and absence of secondary ossification, as late as 21 months of age, at all epiphyseal centers. Only the two forms of achondrogenesis display such a severe and generalized deficiency of enchondral ossification. They can be differentiated from this disorder radiographically by severe shortening of the tubular bones and their abnormalities in membranous ossification, and clinically by their marked micromelia and rapid lethality. This disorder can also be readily differentiated radiographically from other chondrodysplasias that display delayed secondary enchondral ossification, such as spondyloepiphyseal dysplasia congenita, by the extensive involvement of primary endochondral ossification. The pathologic findings at the growth plate can also be utilized to differentiate this disorder from other types of neonatal dwarfism, such as achondrogenesis. The appearance of the clusters of hypertrophic cells, surrounding by dense collagen, resembles the histologic change seen in the metaphyseal chondrodysplasias, but the defect in the metaphyseal dysplasias is less severe and the clusters of hypertrophic cells do not contain calcified cartilage. The dilation of the cisternae of rough endoplasmic reticulum of the chondrocytes is nonspecific and has been observed in several other chondrodysplasias such as the Kniest syndrome and pseudoachondroplasia. The etiology and biochemical basis of this defect and the resultant failure in chondroosseous transformation remain to be determined.
|Original language||English (US)|
|Number of pages||9|
|Journal||Birth Defects: Original Article Series|
|Issue number||3 D|
|State||Published - Jan 1 1977|
ASJC Scopus subject areas
- Developmental Biology