Tetraploid partial hydatidiform moles: two cases with a triple paternal contribution and a 92,XXXY karyotype

In the course of a systematic study of cytogenetics, morphology, and clinical follow-up of hydatidiform moles we encountered two unusual cases of partial hydatidiform moles each with a 92,XXXY karyotype. Previously reported cases of tetraploidy, of 92,XXXX or 92,XXYY karyotype, resulted from a failure of the first mitotic division of a normal zygote. This is to our knowledge the first report of tetraploidy with XXXY sex chromosomes. Study of chromosomal heteromorphisms, isozymes, and restriction fragment length polymorphisms reveal that both present cases resulted from a combination of a haploid ovum with three haploid sets of paternal chromosomes either by the mechanism of trispermy (involving three separate haploid spermatozoa) or through dispermy (involving one haploid and one diploid sperm). Both cases resembled closely partial moles in their morphology; one gave a highly typical clinical picture while the other was recognized at an early voluntary abortion. Partial moles are ordinarily triploids of nearly always diandric constitution that evince focal villous swelling with cistern formation and focal trophoblastic hyperplasia. The findings here presented point to an association of molar phenotype with an excess of paternal over maternal haploid sets.