Isodicentricism

There are many chromosomal variations that cause the 45,X/46,XY karyotype, including malformation (isodicentricism) of the Y chromosomes, deletions of Y chromosome or translocations of Y chromosome segments.

Isodicentric Y chromosome. Apart from deletions, duplications, or both, other structural changes that might alter the natural composition and integrity of the Y chromosome are isodicentricism, truncation, or ring formation [...]