Recognizing the clinical features of Trisomy 13 syndrome.

Recognition of the clinical features of Trisomy 13 syndrome, a common autosomal trisomy, provides the basis for diagnostic testing and counseling of families. This article provides a systematic guide to physical assessment and photographs to enhance recognition of this genetic disorder. The principles of numerical chromosomal abnormalities as related to trisomies are reviewed. An abnormal development of the forebrain, holoprosencephaly, is the most common cranial abnormality in infants with Trisomy 13. The embryology and implications of holoprosencephaly are described. A discussion of antenatal diagnosis of Trisomy 13 and delivery room management is also provided. The diagnosis of Trisomy 13 is confirmed antenatally or after delivery with genetic testing. Prognosis of infants with Trisomy 13 and implications for the infants development are described.