Presence of an extra chromosome 8.
Note: Complete
trisomy 8 is lethal, but most affected individuals show
mosaicism with
craniofacial abnormalities, a short wide neck, multiple joint defects, and deep creases in the palms and soles.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 815 (https://doi.org/10.1515/pac-2015-1202)