A male newborn with severe congenital abnormalities is described with a de-
novo translocation 16;21 resulting in trisomy 16q. Clinical features were c
onsistent with trisomy 16q cases reported in the literature. Molecular anal
ysis indicate a formation mechanism of the rearrangement restricted to post
zygotic mitosis. Therefore, a low recurrence risk for the parents could be
delineated.