trisomy 13
noun
\ -ˈthər(t)-ˈtēn
\
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Medical Definition of trisomy 13
: a congenital condition that is characterized especially by usually severe intellectual disability and by craniofacial, cardiac, ocular, and cerebral abnormalities, is caused by trisomy of the human chromosome numbered 13, and is typically fatal especially within the first six months of life
— called also Patau syndrome