What condition involves a congenital deficiency of abdominal musculature noted at birth?

Eagle-Barrett syndrome, also known as prune belly syndrome, is characterized by a congenital deficiency of abdominal musculature that becomes evident at birth. This condition manifests in a triad of symptoms: abdominal muscle deficiency, urinary tract anomalies, and cryptorchidism (undescended testes in males). The lack of abdominal musculature can lead to significant complications related to the internal organs and affects the normal functioning of the abdominal cavity.

The other conditions listed do not specifically involve an absence of abdominal muscles at birth. Down syndrome is a genetic disorder caused by the presence of an extra chromosome 21, which leads to intellectual disability and various physical traits but does not involve a deficiency of abdominal musculature. Hirschsprung disease, characterized by a lack of nerve cells in the colon leading to severe constipation or intestinal blockage, does not relate to abdominal muscle development. Prader-Willi syndrome is a genetic disorder associated with developmental delays and obesity but similarly does not involve the absence of abdominal muscles.

Therefore, the defining characteristic of Eagle-Barrett syndrome makes it the correct answer, as it directly addresses the question about congenital abdominal muscle deficiency.