Sacral agenesis, also known as hypoplasia of the sacrum or caudal regression syndrome, is a rather obscure and extremely rare congenital condition characterized by spinal deformity in the sacrum (i.e. the spine's caudal partition). It affects an estimated one in 15,000 births.

Affected patients have weak motor function in the area below the normal portion of the spine, as well as impaired sensory function below the level of the affected vertebrae. In its most severe form, sacral genesis can lead to a partial or complete absence of the lumbar spine and even the lower thoracic spine. If severe, the disease is commonly referred to as lumbosacral agenesis.

Sacral agenesis is linked to a number of factors that occur approximately during the third to seventh week of fetal development. By the fourth week of development, the formation of the sacrum (lower back) and corresponding nervous system are usually nearing completion. Factors that facilitate this process are believed to trigger this congenital condition. However, the exact etiology of sacral agenesis remains unknown. It has been speculated that deficiencies in the mother's diet during her pregnancy as well as maternal diabetes are risk factors for sacral genesis in infants. Other less common risk factors have also been enumerated, including exposure to certain organic solvents during the early stage of pregnancy.

sacralagenesis