When reviewing the published literature on constitutional bone diseases, for inclusion in a data-processing system, 6 [human] cases of enchondroplasia affecting the spine were discovered. Similar observations were reported under the name of spondylo-enchondroplasia. Radiological signs and genetic information suggest that this group of affections is a heterogenous one. Vertebral lesions vary greatly in extent, reaching in some cases the level of a spheno-occipital synchrondrosis.