Dysmorphic disorders--an overview.

Clinical delineation of dysmorphic syndromes is important for patient management, family counselling and basic research. Productive areas of research in dysmorphology and developmental biology have included the study of the mouse homologies of human disease. Mutations have been identified in both species in highly conserved 'developmental' genes, and also because of phenotypic similarity of syndromes. Mosaicism--somatic, germline and placental--involving chromosomal aneuploidy, single gene mutations and functional differences between cell lines is an important cause of malformations and syndromes. Many recurrent pattern malformation syndromes of previously unknown cause have now been found to be due to chromosomal microdeletions. Diagnosis has been greatly aided by the molecular cytogenetic technique of fluorescent in situ hybridization.