What other genetic problems might someone have if they have a child with holoprosencephaly?

Multiple: Holoprosencephaly is seen frequently with trisomy 13. It is also found in partial chromasome deletion syndromes for 11, 13 &18. One of my few cases was an affected fraternal twin that also had 21 trisomy Down syndrome (the other twin was normal).

Maybe none: If I am understanding the question correctly, you're asking if someone who has a child with holoporsencephaly has genetic problems themselves. As dr ferfuson said, this problem is sometimes associated with genetic problems *in the kid.* children with these types of problems can be born from perfectly normal parents. It just happens. To be sure, parents can get tested if they want.