Time and natural history: the changing face.

There is a considerable body of knowledge on the changing structures of the craniofacial complex in the anthropology literature, which dates back to the late 19th century. This awareness of change in phenotype has not been emphasized in dysmorphology and incorporated into syndrome diagnosis until recently. In contrast to the anthropological data, where serial craniofacial measurements document different rates of growth in the individual structures of the craniofacial complex, awareness of the evolution of phenotype, in dysmorphology, has been based on an appreciation of a changing gestalt. This work has been carried out principally in Noonan syndrome. Noonan syndrome is a cardiofacial syndrome in which affected individuals may be short and mildly mentally retarded. In this autosomal dominant disorder, a marked change of phenotype with age from the newborn period, infancy, childhood, adolescence, and adulthood has been documented. Similar variation with age is likely to be found in many other dysmorphic syndromes. Increasing insight into the evolution of phenotypes should markedly increase the potential for diagnosis.