PATHOPHYSIOLOGY OF TETRAPLOIDY

Tetraploid fetuses have duplication of both maternal and paternal haploid sets (there is probably normal division of chromosomes and suppression of cytoplasmic cleavage at the first mitotic division).

• All tetraploids are therefore XXXX or XXYY.
• There is duplication of both maternal and paternal chromosomes.
• Some cases of aneuploidy / tetraploidy 94 XXXX, +20 +20 and 94 XXYY, +16 +16 show a meiotic error creating a 24 chromosome gamete followed by a 47 - chromosome zygote and a second error during the first mitotic cleavage producing a 94 - chromosome conceptus.