Definition of Agenesis, sacral

Agenesis, sacral: Failure of formation of all or part of the sacrum (the lowest section of the
spine).
Currarino syndrome is a condition characterized by the combination of:

Partial absence of the sacrum (the lowest portion of spine),
Anorectal (anal and rectal) abnormalities, and
An abnormal mass in front of the sacrum (due to a meningocoele or
teratoma).

The malformations in Currarino syndrome are all in tissues that have their
embryological origin in the tail bud and may reflect disturbances in its
formation during early embryonic life. A mutation (change) in a gene called the
HLXB9 homeobox gene has been identified as responsible for autosomal dominant
Currarino syndrome, also known as hereditary sacral agenesis.