The clinical features of spondyloepiphyseal dysplasia congenita resulting from the substitution of glycine 997 by serine in the alpha 1(II) chain of type II collagen.

The features of a child with spondyloepiphyseal dysplasia congenita resulting from a mutation in one COL2A1 allele were studied. The child was heterozygous for a G to A transition in exon 48 that resulted in the substitution of glycine 997 by serine in the triple helical domain of alpha 1(II) chains of type II collagen. Her longitudinal growth was close to the mean growth curve for children with this chondrodysplasia. Expression of the mutation by chondrocytes would account for the abnormal growth and development of the bones of the limbs and spine. Early expression of the mutation by epithelial cells and later expression by chondrocytes of the developing craniofacial structures would also account for her complex pattern of craniofacial anomalies. The findings in this study confirm that mutations of exon 48 of the COL2A1 gene, that alter the normal Gly-X-Y triplet structure of the corresponding region of alpha 1(II) chains of type II collagen, produce the spondyloepiphyseal dysplasia congenita phenotype.