Congenital abnormality characterized by malformation or absence of the sacrum, usually with associated spinal dysraphism and tethered cord. Presentation can range from mild to life-threatening. It may be an isolated defect or can be found as part of associated syndromes, such as the VACTERL association (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal abnormalities, renal and radial abnormalities, and limb abnormalities).

Other characteristics include narrow hips, hypoplastic gluteal muscles, short intergluteal cleft, sacral dimple, lower limb flexion contractures, clubfeet, and leg atrophy. Neurological abnormalities such as poorly controlled urinary and bowel function are often observed. Most commonly seen in infants born to mothers with diabetes. Treatment is symptomatic.