[Genetics of hydatidiform moles]

Newer genetic investigations show that the complete or classical hydatidiform mole has in over 90% of the cases a diploid female set of chromosomes which is exclusively of paternal origin. The 23 X sperm genom is doubled and the nucleus of the ovocyte is degenerated. In contradistinction the nucleus of the ovocyte persists in partial moles. The normal ontogenesis is also disturbed by a preponderance of paternal genetic material. By melting of 2 instead of 1 paternal germ cell (Dispermia) the genom of partial moles is to 1/3 of maternal and to 2/3 of paternal origin. The triploid set of chromosomes shows usually 69xxy. Whereas the potential of malignancy of partial moles is low a choriocarcinoma results from 2 to 10% of the complete moles. Responsible maybe recessive hereditary mutations of growth controlling genes, which are present in complete moles in a homozygote form due to the doubling of a single paternal set of chromosomes. Total absence of the growth controlling loci of these genes maternally permits an unhibited expression of the growth controlling paternal genes.