Definition:

Sacral defect with anterior meningocele (SDAM), also known as caudal regression syndrome, is a rare malformation that represents a spectrum of caudal anomalies. Clinical findings include varying degrees of agenesis of the vertebral column (usually sacral or lumbosacral spine), as well as anorectal and genitourinary anomalies. The most severe end of this spectrum is known as sirenomelia which is characterized by fused lower limbs. These are caused by developmental field defects of blastogenesis involving the caudal mesoderm and are usually sporadic.