Trisomy 13 (Patau Syndrome; Trisomy D) By Nina N Powell-Hamilton, MD, Sidney Kimmel Medical College at Thomas Jefferson University Reviewed / Revised Dec 2021 | Modified Sep 2022 View Patient Education Diagnosis Treatment More Information Topic Resources Single Transverse Palmar... Trisomy 13 Karyotype (Patau... Trisomy 13 is caused by an extra chromosome 13 and causes abnormal forebrain, midface, and eye development; severe intellectual disability; heart defects; and small birth size.