In Trisomy 13, which feature is a hallmark sign?

In Trisomy 13, a hallmark sign is holoprosencephaly. This condition is characterized by the failure of the embryonic forebrain to properly divide into two hemispheres, which can lead to a range of neurological and facial deformities. Holoprosencephaly is significantly associated with Trisomy 13 and is often evident upon imaging or in the physical examination of infants with this aneuploidy.

The presence of holoprosencephaly can result in facial anomalies such as cyclopia or a proboscis, and other severe malformations that impact neurodevelopment, making it a defining feature of the syndrome. Understanding this relationship is crucial, as it aids in diagnosing Trisomy 13 and recognizing its potential complications early in the management of affected individuals.