Chromosomal and genetic forms of growth failure

This chapter does not deal with single diseases, but gives a general account of chromosomal and genetically caused disturbances of growth; even a complete list and description of the various disorders would, in view of the large number of syndromes involving short stature, exceed its scope. Many chromosomal aberrations are non-viable disturbances of growth that lead to intrauterine amniotic death. Following a brief account of the normal development of the germ cell (gametogenesis, embryogenesis, phenogenesis) to the newborn, the incidence of the various chromosomal disturbances in the different stages of development and the effects on growth are discussed. In the case of chromosomal aberrations, particular attention is paid to the significance of mosaic formation. In addition, the new phenomena of genomic imprinting and uniparental disomy, exemplified by the Prader-Willi syndrome, are dealt with. Uniparental disomy, which was first demonstrated with the aid of molecular genetics, may provide an explanation for the sporadic appearance of many syndromes involving short stature. Many genes and environmental influences are involved in the individual shaping of body size so that a systematic classification of the various syndromes involving short stature is not possible. Finally, attention is drawn to the increased rate of formation of malignant tumours in certain syndromes involving disturbances of growth.