The pathology of cartilage in chondrodysplasias.

The pathology of four types of chondrodysplasias, viz., type II achondrogenesis, thanatophoric dwarfism, Saldino-Noonan syndrome, and chondrodysplasia punctata were studied. In each of these disorders, cells with features similar to the chief and dark chondrocytes of normal hyaline cartilage were seen to be altered in different ways. There was a total absence of chief cells in type II achondrogenesis. All the chondrocytes present were of one variety at different states of maturation, with the fully matured cell having features of dark chondrocytes. The absence of chief cells was associated with marked diminution of interlacunar matrix and failure of growth plate development. The chief chondrocytes in thanatophoric dwarfism appeared diminished in number. They were probably abnormal functionally as evident by their lack of cytoplasmic vacuolation and the formation of thick, occasionally branched collagen in the matrix. The growth plate was stunted and poorly developed. Striking changes involving the dark cells were noted in Saldino-Noonan syndrome, where unusually elongated dark cells were found in groups within abnormal cystic spaces. The chief cells were large and contained abnormal cytoplasmic filaments. There was no formation of a growth plate. In chondrodysplasia punctata, the chief cells were enlarged and abnormally vacuolated. The matrix showed excessive aggregates of coarse granular material. In addition, there were focal accumulations of highly abnormal chief and dark cells with abnormal matrix which contained increased amount of keratan sulphate and culminated in spotty calcification.