Genetic basis for developmental delay/mental retardation

Although developmental delay/mental retardation is a common disorder, the causes remain unknown in about half of the cases. In recent years advances in molecular cytogenetics and molecular genetics have shown that submicroscopic genome abnormalities are a frequent, until now under-recognized cause of mental retardation. The use of new techniques allows recognition of the known clinical entities as well as definition of new disorders. We review today's achievements in this field in the context of recommendations for the rational use of diagnostic procedures in the evaluation of the genetic causes of developmental delay/mental retardation in clinical settings.