The genetics of congenital malformations.

In this paper I have attempted to review briefly both how and why visible chromosome and invisible gene abnormalities may cause congenital malformations and syndromes. The causes may represent nonspecific disturbances in the timing of embryologic events or specific effects on a particular tissue, organ, or cell type. Several different biochemical pathways or structural proteins may impinge upon a single or several embryological events; several genes may be involved in a single pathway, and different changes may affect a single gene. The end result of many of these different processes may well be a similar morphological manifestation. An appreciation and understanding of the potential diversity of genetic causes for a malformation, and the wide variation in the phenotypic expression of malformations or syndromes that is typically seen, is essential if one is to provide adequate medical management to patients and their families. The rapid advances being seen today in the fields of genetics and embryology hold great potential for a true understanding of the developmental biology of, and the ultimate prevention of, congenital malformations.