Identification of the triploid genome by the C-banding method

Genetic studies on hydatidiform moles

Using an historical approach, this article describes how genetic studies have elucidated the two entities into which the syndrome of hydatidiform mole can now be divided. Partial moles are triploid, have a maternal chromosomal set, and are associated with the presence of a fetus. Complete moles lack a fetus and are always diploid and androgenetic in origin, having two sets of paternal chromosomes. They are most often XX and homozygous, the most likely origin being by duplication of a haploid sperm. About 4% of complete moles have been shown to by XY and heterozygous, the most likely origin being by dispermy. The frequency of partial and complete mole observed depends on the method of ascertainment. Among spontaneous abortions, partial moles are more common than complete moles, but among cases having an elective termination of pregnancy because of a prior diagnosis of hydatidiform mole, complete mole is the more common. Patients with either type of mole may require treatment for persistent trophoblastic activity. More prospective studies of cases in which the type of mole has been confirmed by genetic studies are required in order to find out whether (a) patients with complete moles are more likely than those with partial moles to require treatment for persistence of trophoblastic activity after evacuation; and (b) heterozygous complete moles have a different prognosis from the point of view of malignant sequelae than homozygous complete moles.

Genetic studies on hydatidiform moles. I. The origin of partial moles

A study was designed to investigate the genetic origin of hydatidiform moles. Fifty-nine specimens were obtained and, on a histological basis, separated into two entities: complete and partial. The study of the genetic origin of the 15 partial moles, using cytogenetic and biochemical markers, is described. All the partial moles examined cytogenetically were triploid. One had 71 chromosomes. The sex chromosome complements of seven cases were six XXY and one XXX. Origin by dispermy was possible in seven cases and was proven in four. With the use of biochemical markers a maternal contribution was identified in three cases, and the isoenzyme pattern suggested a trisomic state for at least one locus in four cases. The mechanism of origin of partial moles was compared with spontaneously aborted and liveborn triploids. All the patients were followed up for at least 9 months, and none required treatment for persistent trophoblastic activity.