Metabolic disorders of embryogenesis.

Prevention of major physical malformations would represent a significant reduction in the burden of mortality and morbidity in infants and young children. However, preventive and therapeutic approaches must be based on a clear understanding of underlying pathogenic mechanisms. While it is estimated that single gene defects account for up to 10% of cases of major malformation, relatively few of these have been identified and analysed in detail. The recognition of characteristic patterns of developmental anomalies associated with specific enzyme defects has highlighted the important role of the metabolic environment in normal development and offers the possibility of correlating biochemical abnormalities with particular teratogenic effects. Once it is generally appreciated that some forms of structural malformation have a specific biochemical basis, metabolic studies should be performed more often in patients with major developmental anomalies. This should lead to identification of other examples of diseases of this type and the elucidation of molecular mechanisms of human teratogenesis.