Severe achondroplasia: demonstration of probable heterogeneity within this clinical syndrome.

True achondroplasia is a well-delineated and distinct entity as familiar to the layman as it is to the members of the medical profession (Maroteaux and Lamy, 1964). In the past the designation was often assigned to a hotchpotch of entities such as Morquio's disease and spondylo-epiphysial dysplasia (McKusick, 1966; Maroteaux and Lamy, 1959; Jacobsen, 1939). It is considered to be due in all instances to a dominant allele, and is usually the result of a new mutation, as the reproductive fitness of sufferers is much lower than normal (M0rch, 1941). Certainly there is little reason to suppose that there is any genetic heterogeneity among the sufferers from the more commonly seen form of this disorder. The question of whether there might be a different variety of the disease, presenting in a more severe form and with recessive inheritance, arose when there was born to a young Brisbane couple a second child afflicted, like the earlier sib, with a very severe form of chrondrodystrophy associated with multiple congenital defects.